Metals and Materials International

https://doi.org/10.1007/s12540-019-00440-x

Dissimilar Cladding of Ni–Cr–Mo Superalloy over 316L Austenitic

Stainless Steel: Morphologies and Mechanical Properties
A. Evangeline1 · P. Sathiya1

Received: 24 June 2019 / Accepted: 26 August 2019

© The Korean Institute of Metals and Materials 2019

Abstract
The solid solution strengthened Inconel 625, a Ni-based alloy is known for its excellent strength and good corrosion resist-
ance at extreme environments used in thermal plants, boiler tubes, petrochemical industry and power plant. The presence of
Cr content (~ 20 wt%) along with Mo-rich, Nb and Fe makes Ni–Cr–Mo–Nb austenitic alloy called as Inconel 625 to achieve
excellent corrosion resistance property. Using cold metal arc transfer (CMT) cladding, the metallurgical, mechanical and
corrosion properties of Inconel 625 on 316L is evaluated. The process parameters selected includes welding current, torch
angle and travel speed with a constant voltage. From the results of microstructural and EDS inferences, the formation of cel-
lular dendritic structure with secondary phases like Laves phase, complex nitrides along with the interdendritic segregation
of Mo and Nb as well as microsegregation of Cr, Ni and Fe. In case of Ni–Cr–Mo alloy, Ni and Cr contribute to resistance to
corrosion in NaCl environments. The formation of C ­ r2O3 and the passivation action of the clad zone is due to the presence of
Cr. The solid solution effect in Ni–Cr matrix is contributed by the presence of Nb and Mo. Apart from that the strengthening
action happens due to the precipitation of N­ i3 (Al, Ti, Nb) commonly known as γ′, γ″ and MC carbides confirmed through
XRD. Uni-axial tensile tests and Vickers-micro hardness indentation tests were performed on Inconel 625 cladded over
316L. Based on the fractographic results fatigue striations, tear rigdes with river markings, dimples with fibrous structure
and cleavages are observed. Unlike other studies, unique type of cuboidal precipitates are seen, which is due to the presence
of Ti, which form carbonitrides containing Ti, which are further characterised as NbC. The potentiodynamic polarisation
tests is performed on 3.5% NaCl solution. The results suggest that Ni–Cr–Mo alloy protects the substrate from corrosion.

Keywords Cold metal arc transfer cladding · Inconel 625 · 316L · Potentiodynamic polarisation tests

1 Introduction called Cold Metal arc Transfer (CMT) was used. Invented
by Fronius, CMT [4] contains droplet deposition by wire
Application of Ni-based Inconel 625 includes power plants, detachment through wire-motions embedded in the digital
boiler tubes, chemical plants and thermal station due to their process-control. The advantage of Cold Metal arc Transfer
excellent performance at high temperature [1, 2]. The out- (CMT) over Cold Arc (CA) is that CMT puts a unique wire
standing commercial grade Ni–Cr–Mo alloy also known as feed system through digital control for achieving controlled
Inconel 625, which contains secondary intermetallic phases droplet deposition with low amount of heat. CMT is advan-
like Laves phases along with Nb and Fe, is used mainly tageous than CA in case of cladding of dissimilar alloys
because of its notable strength, good fabricability and out- pertaining to its low heat input which confines the appear-
standing corrosion resistance [3]. Owing to its high cost ance of brittle intermetallic compound [5].
and also to protect cheaper base material from corrosion, The droplet deposition assisted by short circuiting is pos-
Inconel 625 is used. To perform the Ni-base clad layers with sible through the retraction motion of the wire was coined by
negligible Fe content, a revolutionary GMAW technique Kah et al. [6]. The findings of Schierl [7] revealed that, CMT
offers less spatter. The fundamentals and principles of short
* P. Sathiya circuiting and droplet detachment motion of CMT cladding
psathiya@nitt.edu are observed by Pickin and Young [8]. Findings reported
by Zhang et al. [9] reveals that the application of CMT in
1
Department of Production Engineering, National Institute dissimilar cladding of Ni-based alloys prevents appearance
of Technology, Tiruchirappalli, Tamil Nadu 620015, India

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of intermetallic compounds, owing to the advantage of low solidification occurs at the primary stage L → γ, (2) a reac-
heat input. tion occurs at eutectic stage L → (γ + NbC), at a wide range
The Ni-based superalloy is known as complicated type of of temperature, (3) a reaction at the eutectic terminal stage
superalloy, because of its many phases [10]. The Ni-based L → (γ + Laves) occurs at lower final temperature. Recent
superalloy contains carbides, austenitic matrix γ and tena- research exemplifies that precipitates present in Nb, C, N
cious sediments of γ′ [11–14]. The two types of Ni-based and Ti during the dissimilar welding of Inconel 625, can
superalloy are solid solution type and precipitation hard- change the solidification behaviour of the alloys [25–28].
ening type. The austenitic matrix phase containing FCC Due to the combined effect of microchemical and micro-
network along with the secondary phases containing FCC structural inferences during the solidification of Ni-based
carbides (MC and ­M23C6), γ″ phase (­ Ni3Nbi), are observed alloys, there exist a new relationship between the metallurgi-
in microstructural characterisation of Inconel 625. cal and mechanical properties of Ni-based alloys.
The loss prone by the high temperature Inconel 625 From the past literatures it has been inferred that cladding
superalloy at elevated temperature includes abrasion, cor- of dissimilar materials by proper implications of cladding
rosion, and oxidation [15–18]. Hence, samples should be conditions, there occurs changes in the chemical composi-
cladded in order to protect the surfaces from damage. tion due to improvement of Fe and C present in Ni–Cr–Mo
Abioye et al. [19] in their work on Inconel 625 cladding alloy results in changes in partially melted zone [29, 30].
over AISI 304, from the microstructural analysis reveal the Similar studies have found out that the precipitates of Ni,
presence of formation of dendrite background phase along Cr, Nb and Ti can change the solidification behaviour of
with the precipitates of carbides in γ background and appear- the alloy.
ance of eutectic phase (Laves phase). At the clad region and Many research have been conducted on metallurgical
also on the interface region towards the clad, formation of and phasic formation of variety of similar cladding with
columnar and cellular dendrites are confirmed by Dinda Inconel–Inconel [31]. The cladding of Inconel 625 using
et al. [20]. CMT technique seems to be revolutionary and potentially
The deposition of Inconel 625 on carbon steel using CMT tensile stresses developed during the weld cooling cycle,
exhibits segregation of Ni, Mo, Nb and Cr along the dendrite producing microfissuring high temperature applications.
core. Rozmus et al. examined the cladding of Ni–Cr–Mo Very few information have been given about the dissimilar
alloy using GMAW, GTAW and CMT and identified that the bonding between Inconel 625 and 316L in terms of forma-
metallurgical and mechanical properties of cladding relay tion of secondary precipitates and segregation of Mo. Here a
on the process applied and the as received chemical com- unique cubic precipitates rich in Ti, having a complex struc-
position of the base material. Ola et al. studied about CMT ture containing titanium nitrite encompassed by NbTiC is
cladding of Inconel 718 filler over the same substrate and observed through SEM.
found out that defect free clads with less than 10% dilution
is possible.
Xu et al. [21] evaluated the cladding microstructural 2 Material and Sample Preparation
inferences of Inconel 625 over 316L stainless steel substrate.
From the findings the columnar and coaxial dendrites were The required samples of dimension 200 mm × 100 mm x
seen in the cladded and interface zone towards the clad cel- 10 mm thickness are cladded with Inconel 625 over 316L.
lular structure is observed along with γ phase. Verdi et al. Table 1 shows the as received chemical composition 316L
[22] worked on Inconel 625 cladded over ­Gr22 ferritic steel stainless steel. Inconel 625 filler wire of diameter 1.2 mm
(ASTM A387) base material and observed similar results to is used and the chemical composition is clearly listed in
that of previous studies. DuPont [23] identified that using Table 1.
TIG cladding of Inconel 625, γ + Laves phase are produced The clad, interface and the substrate region of the sam-
during crystallization and derived the following: ple was thoroughly polished using SiC papers made of grit
size 220, 400, 600, 800, 1000, 1200 and also cleaning them
L → 𝛾 → L + 𝛾 → L + 𝛾 + Laves → 𝛾 + Laves. (1) with acetone prevents the sample from oxidation and other
The Nb and Mo get separated from the phases formed at contaminants.
high remperatures. Limited studies are performed on the
metallographical aspects of CMT cladding using Ni-based 2.1 Cold Metal Arc Transfer (CMT) Cladding Process
superalloy [23].
Lots of experimental work were done to identify the Fronius CMT 7000 VR machine is used in cladding of
solidification action of Nb present in the Ni-based super- Inconel 625 over 316L substrate as shown in Fig. 1. The
alloys. DuPont and Robino [24] findings revealed that greater contact angles are possible with pulsed-CMT mode
solidification of Inconel follows three stages, which are: (1) when compared with the conventional type of CMT mode.

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Table 1  As received chemical composition of 316L and Inconel 625

Base metal—AISI 316L wt%
C Mn Si Cr Ni Mo P S N Fe

0.02% 2.00% 0.75% 16.00%–18.00% 10.00%–14.00% 2.00%–3.00% 0.05% 0.03% 0.10% Bal.
Filler wire—Inconel 625 wt%
Cr Ni Mo Co Nb + Ta C

20%–23% 58–Bal% 8%–10% 0%–1% 3.1%–4.1% 0%–0.1%

Table 2  Experimental parameters

Exp. no. Welding cur- Voltage (v) Torch Welding
rent (Amps) angle speed (mm/
(deg) min)
Symbol (I) (V) (TA) (S)

C1 140 21 80 175
C2 160 21 60 150
C3 180 21 70 125

by the welding arc voltage. Similarly, travel speed has a

direct influence on clad bead and depth of penetration for a
given welding current and corresponding voltage.
Based on the trial and error runs, for welding current of
140 A, 160 A and 180 A corresponding samples C1, C2 and
C3 were selected respectively. The parameters are shown in
Table 2.

2.2 Microstructural Analysis

Before cladding of Inconel 625, the substrate 316L surface

was ground with 120 grit SiC paper and then cleansed thor-
oughly with acetone. Again after cladding, the bead and the
Fig. 1  Fronius CMT 7000 VR machine set up substrate were cleansed with the help of wire brush before
each subsequent metal deposition.
Inconel 625 cladded on 316L plates of dimension
The variations in speed can be controlled using 6-axis 500 × 100 × 10 mm were drawn into required length, further
Yaskawa Motoman robot. The robotic arm controls the travel drawn into strips of dimension with the help of MW250 a
speed and path while other welding parameters torch angle, high-precision micro wire cutting EDM into dimensions of
voltage and current can be controlled in remote control unit 500 × 10 × 10 mm. Further the samples were sliced down
(RCU) inbuilt in the CMT Fronius system. with the help of Master SSA abrasive cutting machine into
Argon as a shielding gas with the flow rate of 15–20 L/ dimensions of 20 × 10 × 10 mm thickness.
min is used. The nozzle diameter is around 3.2 mm. 70 bar of The cladded samples C1, C2 and C3 were swabbed
cylinder pressure is maintained. The quality of the clad bead with ethanol prior to cladding inorder to get rid of impuri-
lies on the selected process parameters. The welding current ties, such as grease and oil, which are usually present soon
(140, 160 and 180 Amps) voltage (17 volts), torch angle after the EDM cutting process. Transverse section of the
(60°, 70° and 80°), travel speed (125, 175 and 150 mm/min) clad beads follow standard metallographic procedure while
are taken as the cladding process parameters, respectively. polishing the samples. The polishing by SiC emery papers
The welding current has a direct influence on depth of pen- of grades 220, 400, 600, 800, 1000 and 1200 were done
etration and extends up to the fusion zone on the base metal. for microstructural characterization. The electrolytic etch-
The shape and bead appearance are controlled and directed ing applied for Inconel 625 includes 10% of ammonium

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persulphate solution at 3.5 V for 5 s and etchants applied sliced samples consists of 1 mm thickness respectively.
for base 316L includes concentrated aqua regia (3:1) From the past literatures, the samples with 10 mm gauge
3HCl:HNO3 for a minute. length are similar to that of micro tensile samples taken
To obtain microstructural characterization of the trans- for analysis [32].
verse cross sections of the Inconel 625, cladded sample was
investigated with the help of LYNX Stereozoom Microscope
with 5 MP C MOS Camera along with the Image Acquisi- 2.5 Potentiodynamic Polarization Technique
tion Software. The elemental phasic characterization of the for Corrosion Resistance
sample comprising substrate, interface and clad region were
investigated using scanning electron microscopy (SEM) The corrosion behavior of Inconel 625 clad samples of
(Hitachi S-3000 H) connected with energy dispersive spec- dimensions 20x10x10 mm, are investigated using potentio-
trometer (EDS). X-ray diffraction (XRD) was acquired to dynamic polarization test at 24 °C in 3.5% NaCl solution,
determine phasic formation. and it was performed as per ASTM G61-86 standard using
IVIUM electrochemical workstation. The workstation con-
2.3 Microhardness Measurement tains one reference electrode composed of saturated calo-
mel electrode (SCE), one counter electrode composed of
The measurement of microhardness was done with the help graphite and sample acts as working electrode.
of Vickers microhardness indentation tester with ASTM Initial delay of 10 s is given in order to generate an open
E384 (Make: Wilson Hardness 402 MVD) with a loading circuit potential (OCP). Keeping scan rate at 0.8 mv/s, cor-
force of 500 gf and dwell time of 10 s. Microhardness of the responding Tafel plot was calculated between − 1 v/SCE
samples were evaluated from the center of the clad region to + 1 v/SCE for samples C1, C2 and C3. The necessary
towards the topmost surface of the base metal to its bottom parameters are calculated once the IVIUM soft electro-
with a spacing of 2 mm between successive points. chemistry software gets installed. The rate at which the
The readings are measured initially from the topmost clad samples gets corroded and corrosion current density are
region, then gradually moving towards the interface and base formulated by the following equation [32]:
region, perpendicular to the direction of cladding.
Corrosion rate = 0.13 ∗ Icorr ∗ E.W.∕A ∗ d (2)
2.4 Tensile Testing where ­Icorr, corrosion current density; E.W, equivalent
weight of the sample used in (g/eq); A, area in c­ m2; d, den-
Using Instron universal testing machine (UTM), the uniaxial sity (in g/cm3).
tensile testing was performed on the samples C1, C2 and C3 The equivalent weight of 316L substrate is found to be
as per ASTM: E8/8 M standard. of 25.50 g/eq and density of 8 g/cm3. Similarly, equivalent
The tests performed on the base, interface and clad weight of Inconel 625 filler wire found to be of 25.573 g/
region, each distinctively from three different heat input eq and density of 8.44 g/cm 3. Chemical composition of
taken from (Table 2) as shown in Fig. 2. A 50 kN UTM 316L base and Inconel 625 filler wire are tested initially
is used along with 1 mm/min cross head speed. The sam- and then obtained microhardness values are 218 H ­ V 0.5
ples C1, C2 and C3 region of the clad, interface and base and 231 ­HV0.5 and calculated corrosion density of round
region are sliced parallel to the direction of cladding. The 8.73E−06 A/cm 2 . Further SEM analysis followed by
EDAX is taken for the respective corroded surfaces [33].

Fig. 2  Geometric profile a sliced tensile samples from base, interface and clad portion. b Required details about sample dimension

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3 Results and Discussion (0.06 × V × I)

H = (3)
S
3.1 Macrostructure of the Cladding
where V, voltage in volts; I, welding current in ampere; S,
welding speed in mm/min.
The clad bead appearance of Inconel 625 on substrate 316L
From Eq. (3), the required heat input for the sample C1,
is shown in Fig. 3.
C2 and C3 are summarised in Table 3. From the findings
C1, C2 and C3 in Fig. 4a–c shows the measured depth
of Kumar et al. changing of welding current and travel
of penetration (DOP) region and dilution of the clad bead.
speed, brings a change in the depth of penetration and hence
The depth of penetration calculated from the stereozoom
increases heat input along with the depth of penetration [35].
macroscope at a magnification of 20× has a linear relation
From Fig. 4 a–c, it is observed that in sample C2 (Fig. 4b)
with the heat input produced in the samples. As welding
because of its inverse relationship with the travel speed,
current increases, heat input also increases, but decreases
attains lower heat input. The calculated heat input in kJ/
with travel speed [33].
mm for C1, C2 and C3 samples (0.856, 0.669 and 0.918)
Heat input H is drawn from the following relation [34],
respectively. The selected parameters for cladding for the
respective sample C2 is found to be satisfied with the depth
of penetration (520 μm) and with the lowest heat input.
The clad bead portrays highly smooth geometric configu-
ration and without any undercut or cracks.
The transverse appearance of the bead shows the con-
nection between bead geometry and process parameters.
The geometry changes in accordance with welding current.

Table 3  Heat input for the samples C1, C2 and C3

Sample C1 C2 C3

Heat Input (kJ/mm) 0.856 0.699 0.918

Fig. 3  Typical appearance of the clad bead

Fig. 4  Stereo macrographs of

sample (a) C1, (b) C2 and (c)
C3, respectively

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Depending on the amount of heat input, the welding cur- from the filler metal region and substrate (­ As + Afm) gives
rent increases (140 A, 160 A, 180 A) with an increase in the dilution value ( D = As+Afm
As
).
depth of penetration and wider beads are achieved. Increase The grain size measurement are carried out using Image
in percentage of dilution increases the welding current [27]. analysis (ASTM E112) using Dexel Metallography software
Increase of heat input, decreases the surface tension, as rise on the microstructural images taken at 200X zoom magnifi-
of liquid metal temperature results in wettability action. cation in the transverse direction.
Increase of heat input, increases the welding current but
decreases the welding speed [33].
The calculated heat input for the sample shown in Eq. (3) 3.1.1 Direct Effect of Process Parameters on the Geometry
are projected in Table 3. The investigation made by Kumar of Clad Bead
et al. by varying both welding current and travel speed,
increase in depth of penetration is achieved along with the The geometry of the clad beads were analysed. The dilution
heat input [35]. (%), depth of penetration (mm) and heat input (kJ/mm) were
From Eq. (3), the calculated Heat input in kJ/mm are calculated see Table 4. The geometry of the clad beads were
tabulated in Table 3. characterised by using optical microscopy (OM) for each
The observed heat input (0.856–0.699 kJ/mm) decreases sample (C1, C2 and C3) for three different trails of weld-
with the increase of welding speed (125–175 mm/min). The ing current (I) and travel speed (S). Few findings are drawn
microstructural investigation of the cladded samples based from the experimental trials. Increase of welding current
on the selected parameters ends up in good clad qualities increases the bead width, reason may be attributed to high
with no porosity nor spatter along with lesser dilution (9.3%) magnitude of current producing greater force on the molten
found for C3 and high aspect ratio (2.6). Since CMT is a metal droplet enabling the spattering action which keeps the
constant current process, the efficiency of the deposition welding current constant as welding speed increases. Thus
remains constant, while bead width and depth increases less amount of metal gets deposited over the substrate and
with reduction in reinforcement height. The uniqueness of ultimately lesser driving force is utilised for the molten weld
CMT is that as heat input increases, metal deposition also pool to create bonding strength on the base metal. The heat
gets increased. Thus a portion of heat input gets consumed input has an adverse effect on the depth of penetration since
in the melting process, so spreading ability of the droplet on it is proportional to the current (owing to the combination
the base plate increases. of increased centrifugal and coulomb’s forces). As current
The clad beads were observed to be defect free with no increases, reinforcement height decreases, reason due to the
pores as shown in Fig. 4a–c. Based on clad bead geometry depth of penetration and the force created on the molten
analysis, sample C3, (I = 180 Amps, V = 17 volts, TA = 80° metal pool, at an increased welding speed.
and S = 175 mm/min), results in minimum dilution and more
bead width. The higher heat input of C3 sample is the reason
behind minimal dilution. Heat transfer occurs at the interface 3.2 Microstructural Analysis
containing Inconel 625 with 316L due to the effect of heat
conduction from the melt pool to the base metal 316L. Fig- The microscopic analysis obtained from the optical micros-
ure 4a–c shows the dilution and bead geometry of the clad- copy revealed that cladding of Inconel 625 over 316L pro-
ded portion and Table 4 presents the comparison of process duces no porosity, zero incomplete fusion and spatter free
parameters and measured bead profiles. or no other flaws with minimal cracking and contains excel-
Using metallographic method, the dilution (D) are meas- lent metallurgical adhesion to the steel substrate as shown
ured from the geometric cross sectional areas of the clad in Fig. 5a–e.
region i.e.) filler metal and base region i.e.) substrate. The The microstructural image of cladded portion contain-
ratio of area of substrate (­ As) to the total cross sectional area ing Inconel 625 clad layers comprises of cellular-dendritic

Table 4  Comparison of process parameters and measured bead profiles

S. no. Current I Voltage (v) Torch angle Welding speed, S Depth of penetra- Heat input Dilution D (%) Average
(Amps) (deg) (mm/min) tion, (mm) (kJ/mm) grain size
(µm)

C1 140 17 60 125 7.613 0.856 35.71 15.8

C2 160 17 70 175 2.443 0.699 28.5 19.3
C3 180 17 80 150 2.342 0.918 9.3 17.8

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Fig. 5  Typical microstructural image of Inconel 625 on 316L. (a) partially melted zone (b) HAZ regio (c) substrate region (d) fusion boundary
zone

structure. The growth of the dendritic arm lies parallel to the

heat flow direction as shown in Fig. 5b.
The Inconel 625 cladding by cold metal arc transfer pro-
cess allows rapid solidification process to take place which
starts with formation of γ phase. For Inconel alloys, with
absence of Nb composition, L/γ transformation is identified
in non eutectic reaction [21, 22]. The Nb or B composition
in Inconel 625 [23, 24] forms precipitates close to the inter-
face region shown in Fig. 6. The solubility nature of Nb and
Mo in Nickel is minimised by the presence of other alloying
elements. Dendrites with γ phase appears as there is a drop
in the level of liquid solidification. Remaining part of the
liquid contains Nb and Mo. The segregation of dendrites
rich in Nb and Mo at the fusion boundary regions, may be
reason behind the formation of interdendritic region [12].
Scanning electron microscopy analyses the metallurgical Fig. 6  Fusion zone containing Inconel 625 cladded over 316L is
characteristics of the cladding. The presence of γ phase and shown at higher magnification
secondary phases are shown in Fig. 7. Elemental distribution
spectroscopy results for Inconel 625 cladded region along
with elemental mapping are revealed in Fig. 9c. The results
of SEM–EDS reveals that due to strong segregation, the Ni From the SEM inferences, the MX precipitates and γ matrix
and Cr move to the dendritic regions and diffusion action are observed in the clad portion of Inconel 625.
takes Mo and Nb to the interdendritic region. Formation of primary Ni-based γ matrix is visible on
From Fig. 7, the segregation action of Nb, results in Laves the clad region and secondary solidification micro con-
or NbC like secondary phase formation. Du Pont et al. [24] stituent elements are seen along the interdendritic region.
findings reveal that the succession of formation of NbC and From Fig. 8 C1 sample with the lower current of 140A,
Laves phase in Ni–Cr–Mo superalloy (~ 3.5 wt% of Nb) shows intergranular microfissuring in partially melted
brings the following: zone (PMZ), and absence of liquation is observed in the
samples C2 and C3.
L → L + γ → L + γ + NbC → γ + NbC + Laves.
(4)
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in minimal intergranular liquation in HAZ. This is the rea-

son behind low amount of tensile stresses produced during
welding.
The nature of crack has been revealed. The Fig. 8 shows
the micrograph of the HAZ zone closer to the interface.
Generally nearer to the interface zone, the austenitic grains
far away are larger and nearer to crack are smaller. This is
because region close to interface are exhibited to high tem-
peratures due to austenisation followed by growth of grains.
Due to increased austenisation, complete dissolution of car-
bides and formation of harder martensite are observed. This
is the reason for the decreased hardness as the prior grains
approach crack region and crack cannot propagate through
the grains resulting in lower hardness.
From the previous studies, the contraction of the bead
Fig. 7  SEM micrograph taken along the Inconel 625 Clad region during solidification and sudden cooling to preheat tem-
showing Laves phase as well as secondary phase formation perature results in thermal contraction which is resisted by
the substrate end up in tensile residual stress in transverse
direction. This causes generation of high tensile stresses at
the substrate.
In this work, hence depth/volume of austenite formation
and subsequent martensite is small, it produces lower stress
generation. The reason claiming to reduction in thickness
of martensite layer and thus small cracks appear. Since
Ni–Cr–Mo alloy is characterised by low residual stress. The
very less amount of residual stress leads to small cracks on
the PMZ zone (Fig. 8).

3.3 X‑ray Diffraction

The formation of γ–Ni phase called as the base phase of Ni-

based superalloy is confirmed from the XRD results shown
in Fig. 10. The γ, γ′, γ″ phases and MC carbide are related
to the peaks, hence γ′, γ″ phases and MC carbides are dif-
Fig. 8  A minimal intergranular liquation zone in HAZ shown in sam- ficult to be identified. Since these phases are present in lower
ple C1 quantities, becomes a reason for not recognising them.
Taking EDS for the dark gray areas (B), it was found to be
rich in Mo, Cr, Nickel and Nb shown in Fig. 11.
The intergranular liquation initiates microfissuring in Figure 12 shows that grains are present in the dark gray
Ni–Cr–Mo alloys. From the previous studies microfissuring area (B), in between the dark gray area are the light gray
are not observed in CMT. Present work stays as an excep- area (A) and dark particles that envelope the light gray areas.
tion from other studies. The reason for the occurrence of The white particles seen alongside are found to be Nb-rich,
microfissuring is due to the tensile stresses produced dur- contains Nickel, Ti, Mo, Cr. Figure 12 (E) depicts the black
ing weld cooling cycle causing decohesion along liquated blades rich in Cr, Nb, Mo and Ni. XRD analysis of Inconel
regions [32]. The absence of microfissuring is mainly due to 625 cladded region have been shown in Fig. 11. From the
low heat input on C2 (0.699 kJ/mm) and low tensile stresses Electron Dispersive Spectrometry analysis results, area B
produced. contains 41.78 wt% nickel, 19.90 wt% Cr, 23.40 wt% Mo
The formation of liquation in HAZ is a common phenom- and elements such as Nb, Fe, W and Ti. In the non-magnetic
enon in Ni–Cr–Mo alloy. Microfissuring occurs only when phase, the continuous matrix phase γ comprises of FCC
the tensile stresses created during cooling causes decohe- structure, containing higher percent of solid solubility alloy-
sion along grain boundaries. EDS elemental mapping con- ing elements like iron, Cr, Mo and tungsten. The γ phase is
firms the presence of Mo-rich precipitates. Generally at low the prime phase of any Ni-based alloy [4, 5, 19, 28]. From
heat input, CMT produces small HAZ zone which results the findings of XRD, region B has the phase γ. Since weight

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Fig. 9  a SEM micrograph

showing Mo-rich precipitate,
b EDAX showing percentage
composition present, c EDS
pattern showing Mo content in
sample C1

Fig. 10  XRD spectrum for clad

beads C1, C2 and C3 containing
Inconel 625 cladded over 316L

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Fig. 11  SEM micrograph showing increase in Ti content forming a bulk phase

percent of elements in region (E) is closer to the region (B), move away from the dendrite center and joins the molten
there is a chance for the formation of γ phase. region round the dendrite. Also elements like Ni, Cr and Fe
Formation of carbides is visible in region (C), which is transmigrate towards γ dendrites. The increased amount of
confirmed by the presence of Cr and carbon. Taking region Mo and Nb in the molten state during solidification gives
A, 41.7 wt% Ni, 19.90 wt% Cr and 23.45 wt% Mo and rise to eutectic compound γ/Laves.
13 wt% niobium were identified. The elements present in
the intermetallic compound ­Ni3Nb, lies coherent to the γ 3.4 Microhardness Measurement
phase leading to the formation of the phase γ′ or γ′′. The
low thermal gradient in the coaxial region is the reason for Traverse microhardness readings resulted from the Inconel
the continuous lave phase. γ dendritic phase appears in the 625 clad region to the lower part of the base metal meas-
solidification of Inconel 625, where the Nb and Mo elements ured with the help of Vickers micro hardness indentation
with a 500 gf applied load and a dwell time of 10 s. The
microhardness values of sample C1–C3 in Fig. 13 observes
a sharp decrease in the hardness value of the sample across
the interface. Vickers microhardness measurements matches
with the findings obtained from the metallurgical charac-
terisation and confirmed through SEM images, exhibiting
homogenous microstructural features along the interface.
265 ± 25 ­HV0.5, 200 ± 20 ­HV0.5 and 190 ± 15 H ­ V0.5, are the
resulted hardness value corresponding to clad, interface and
base region respectively.
No significant changes in the hardness values is observed.
The lower heat input and fast cooling rate tends to decrease
the primary dendritic arm spacing, which may be the reason
for the increase of hardness value in clad region. The higher
hardness value at Inconel 625 clad portion is mainly because
of the enrichment of Cr, Nb, Mo and C.
Taking Hall–Petch relationship into account, the hardness
Fig. 12  SEM micrographs revealing the dark and light areas rich in value tends to decrease with increase of grain size at room
Mo, Cr, Ni and Nb temperature. For a solid solution strengthened superalloy

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Fig. 13  Microhardness profile of the experiments

like Ni–Cr–Mo alloy, major factor elements which decide C3 respectively are tested and graphs between their stress
the hardness are Mo and Nb. From the confirmation results and strain indicated in Fig. 14. From the stress–strain
from SEM/EDS the higher hardness is attributed due to the curves, the ultimate tensile strength, percentage of elon-
finer microstructure and impact of segregation of precipi- gation and yield strength are calculated and drawn in
tates like Mo and Nb. The dissolution of carbides inside the Table 5. From the figure, the highest tensile strength falls
grains and Mo-rich precipitates along the grain boundaries on the cladded zone (907 MPa) and the tensile strength
are the reason behind the variation of hardness in the clad of interface zone (721 MPa) which is higher than that of
region [36]. base material (704 MPa). Taking percentage of elongation
The presence of carbides and intermetallics also contrib- into consideration, elongation of base material (56.1%) is
ute to higher hardness. In addition to the growth of columnar critically higher than that of cladded zone (29.8%). The
microstructures nearer to the fusion boundary zone and the yield strength of Inconel 625 cladded zone (533) is slightly
hard intermetallics also enhance the hardness along the clad increased than the interface zone (433).
region. The indentation mark impinged on the clad area indi- From the Table 5, C denotes Clad portion, I denotes
cates better bonding between the particles. Interface portion and B denotes Base portion.
The hardness of carbides namely MC is also higher, Considering the cladded zone, as the tensile strength
which can improve the resistance to deformation. attains 907 MPa, showing good bonding and high tempera-
The Laves phase morphology exhibits slightly lower hard- ture mechanical characteristics. Higher the tensile strength
ness value, but hardness along the clad region increases with in the cladded area implies good bonding between the sub-
increase in speed. Thus it is revealed that, eutectic carbides strate and clad with no defects.
MC formed as hard particles to hamper the grain boundary It is concluded that the hardness values and the ten-
dislocation, gives out improved hardness. sile results match each other in case of dissimilar clad-
ding. Considering past literatures tensile failures peep
3.5 Tensile Testing Results through in case of AISI 416 attributing to low hardness
and strength. Here, with Inconel 625 negligible traces of
The summarised results of the tensile tests for cladded failure occured in HAZ claiming to the presence of carbon
samples are observed in Table 5. The samples C1, C2 and enriched martensite which gave enough strength.

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Table 5  Tensile results of the Sample type Sample no. Yield tensile strength Ultimate tensile Elongation (%)
clad, interface and substrate for (MPa) strength (MPa)
C1, C2 and C3 samples
C1 C1 C 533 907 29.8
C1 I 421 721 33.6
C1 B 430 704 56.1
C2 C2 C 551 906 35.2
C2 I 464 795 34.3
C2 B 439 713 55.1
C3 C3 C 562 971 34.2
C3 I 482 761 32.5
C3 B 412 658 58.0

Fig. 14  Curve denoting the

stress versus strain plots for
samples (C1, C2 and C3) from
sliced tensile specimens taken
along clad, interface and base
region

3.6 Fractographic Observation

In general, the nature of fracture depends on the material,

temperature, state of stress and rate of loading. Figure 15
shows the fractographic SEM images of samples C1, C2
and C3 respectively. Tear ridges with river markings shown
in Fig. 15 occurs due to shear failure which shows a cleav-
age fracture. The formation of cleavage fracture signifies
the chance for the initiation of crack at the grain boundary.
The appearance of carbides and intermetallic precipitates
present at the grain boundaries serves as the reason for crack
initiation.
The ductile mode of fracture in the form of dimpled rup-
ture, exhibited by cup and cone-like depression is shown
in Fig. 16a. This reveals that fracture occurs mainly due
to density in slip planes in crystal orientation. The second-
ary precipitates are the major reason for the occurrence of Fig. 15  SEM fractography taken for sample C3 showing cleavage and
macrovoids [35]. But the secondary intermetallic phases dimples with fibrous network

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fibrous with dimpled network. The appearance of the voids

are spherical in nature and of smaller size.
The formation of fatigue striations shown in Fig. 16b
reveals that Inconel 625 contains combination of mechani-
cal properties; though it undergoes hardening process and
contains a high resistance limit, owing to its nature of duc-
tility, it ends up in bandings. Macrovoid coalescence was
seen along the fast fracture region. Figure 16c shows the
fracture area of sample prone to a maximum ultimate stress
of 742 MPa, which attributed to the formation of subsequent
fatigue marks of shear slips and beachmarks. Crack nucle-
ated by the effect of discontinuous surface. The presence of
macrovoids coalescence appear mostly in the fast fracture
area due to the dimpled network formation.

3.7 Corrosion Potential Tests

The corrosion rate (­ CRate), corrosion potential ­(Ecorr) and

corrosion current density ­(Icorr) are the necessary param-
eters taken to perform potentiodynamic polarisation tests.
The measurement of corrosion potential were done using
3.5% NaCl solution. Table 6 displays the corrosion param-
eters and their corresponding results in terms of corrosion
current density (­ Icorr), corrosion potential (Ecorr) and cor-
rosion rate ­(CRate). Table 6 and the corresponding Fig. 17
shows the selected corrosion parameters (for clad and base
region). The SEM micrographs showing cross sectioned
view of clad and substrate with good bonding in terms of
­Ecorr, ­Icorr and ­CRate. The corrosion was performed under
de aerated 3.5 wt% NaCl solution at 37.4 °C. Compared to
the substrate, the clad region exhibits improved resistance
to corrosion. The Inconel clad region exhibits passivated
region at minimum current density of 4.0 × 10−3 mA cm−2
than the substrate which passivated at 1.5 × 10−3 mA cm−2.
The formation of passive film layer hampers huge loss of
material at maximum current density, thus minimum current
density shows an improved corrosion resistance.
The main role of the breakdown potential is to bare the
formation of localised attack on the passive film. The wider
passive region of clad layer exhibits breakdown potential of
432 ± 5 mV (wrt SCE electrode). The breakdown potential
for substrate comes round 270 ± 10 mV (SCE electrode) and
a sudden increase in current density with negligible change
Fig. 16  Fractographic images showing macro-void coalescence, in potential is observed. This predicts the occurrence of pit-
fatigue striations and cracked boundaries. (a) cup and cone like ting corrosion on the substrate.
depression (b) macro-void coalescence and fatigue striations (c) dim-
Figure 17 shows the potentiodynamic polarization nature
ple network
of the Inconel 625 cladding, interface area and 316L base
area in 3.5% NaCl solution.
like γ′ and γ′′ coalescence, initiate, grow and over a period Figure 18 shows the results obtained from SEM analysis,
plastic deformation happens at the intervoids before frac- pits are noticed on the corroded area and white like flakes
ture occurs [15]. From Fig. 16b, it’s been clear that fracture indicate the presence of Mo and Nb rich precipitates. The
initiates from the center of the sample and gets extended by polarisation curve ensures the presence of localised pits on
shear separation and the nature of the fracture seems to be the corroded surface.

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Table 6  Corrosion parameters Material Reference electrode Corrosion performance

[corrosion potential ­(Ecorr),
corrosion current density (­ Icorr) Ecorr (mV) Icorr (mA cm−2) RP (ohm) CRate (mm/year)
and corrosion rate ­(CRate)] and
their results Base 316L Saturated calomel electrode (SCE) − 0.4624 0.000157 17,820 0.0005
C1 (worst) Saturated calomel electrode (SCE) − 0.3396 0.000158 18,900 0.01157
C2 Saturated calomel electrode (SCE) − 0.3914 0.000158 20,004 0.0083
C3 (best) Saturated calomel electrode (SCE) − 0.2462 0.000452 48,765 0.00330

corrosion potential and maximum passive current density

which all indicates minimum corrosion resistance.
The reason is that, the corrosion appears uniformly on the
surface of the clad, since no inception of pits on the surface.
The matrix area was slightly disturbed due to the dark matrix
encompassed by grey corrosion product. But the precipitates
remain unaffected [33]. The dendritic matrix acts as sacrifi-
cial anode after being attacked by corrosion. Confirmation
through SEM on two areas A and B revealed that, the pres-
ence of O exhibits that core dendrites suffer oxidation head-
ing to the formation of compounds of Mo shown in Fig. 19.
The light grey B contains negligible amount of O, still hold-
ing some amount of Nb and Mo. Thus the negligible O and
Fig. 17  Potentiodynamic curves Inconel 625 laser clad layers and
unperceivable change reveals that B is not prone to corrosion
316L (as received) substrate in de-aerated 3.5 wt% NaCl solution at attack. The absence of ingress of electrolyte inside the clad
37.4 °C layer confirms that substrate is fully protected by Ni–Cr–Mo
from the action of corrosion [38].
Considering the Inconel 625 clad zone and interface zone,
the base 316L shows slightly higher corrosion potential and
their difference among clad, interface and base region is only
about 60 mV. Taking Cl-rich environment into considera-
tion, more chances exist for pitting corrosion to occur due
to constant pitting potential. At the narrow passive density,
the increase of current density with no change in potential
is observed. Taking 3.5% NaCl solution, the interface region
and substrate show minimum resistance to pitting corrosion
than Inconel 625 cladded area. According to Table 6, the
increase of corrosion resistance is mainly due to the pres-
ence of Cr and Mo-rich Fe–Ni based alloys (Table 7).
As a result, the best corrosion performance in NaCl solu-
tion is observed on the Inconel 625 cladded region. Fig-
ure 20a, b shows the SEM micrographs of a—sample C3
and b—sample C1 containing Inconel 625 clad region before
corrosion tests. In Fig. 20a, b SEM micrographs of sample
Fig. 18  Mo and Ni rich precipitates scattered as white particles on the C3 and C1 before the start of potentiodynmic polarisation
Ni matrix
test is shown. Samples are polished using SiC papers of
grade 600, 800, 1000 and 1200 followed by etching with
chemical reagents namely aqua regia ­(3HNO3: 3HCl).
In the transpassive region of the Inconel layer, the cur- Similarly in Fig. 21a, b SEM micrographs of sample C3
rent density gradient against potential is very minimum, and C1 after the completion of corrosion tests are shown.
indicating that passive layer is free from damage nuclei. The samples C1 and C3 contains dendritic microstructure as
On comparison of the corrosion potential, clad layer shown from both Figs. 20a, b and 21a, b. The grain bounda-
appears to be free from damage [37]. The substrate with Fe ries are shown by visible bright regions and the columnar
content shows minimum breakdown potential, minimum dendrite cores are revealed by dark regions seen in Figs. 20a,

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Fig. 19  X-ray mapping done on the clad layer of Inconel 625 after potentiodynamic polarisation test in de-aerated 3.5% NaCl solution

Table 7  Composition analysis Symbol O Cr Fe Ni Nb Mo

(wt%) of two different region A
and B identified through SEM A 16.5 18.7 1.6 42.2 6 14.98
in figure
B 3.2 27.6 1.0 58.8 7.3 9.8

Fig. 20  a, b SEM micrograph showing samples a sample C3, b sample C1 before potentiodynamic polarisation tests

b and 21a, b [26]. The reason for the bright appearance is match with the chemical composition analyzed using the
due to the formation of oxides and Nb carbide on the grain spectrometer. Taking Nb, it was about four times higher at
boundaries [28]. Taking sample C1 in Fig. 21b corrosion is the grain boundary compared to its sourrending, and the Ni,
visible by the irregular rugged nature of the grain bound- Cr composition comes around 1/3 and 1/2 of those present
ary, showing a contrast to sample C1 before corrosion in in the transgranular region.
Fig. 20b. After corrosion, the shape of the grain boundary can be
Figure 22 shows the energy-dispersive X-ray spectros- clearly seen. The presence of corrosion is confirmed by the
copy (EDS) examination of chemical composition of ele- precipitation of NbC shown in Fig. 23. The corrosion gets
ments. Majority of elements as Ni and Cr were found to initiated along the transgranular region and it is confirmed by

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Fig. 21  a, b SEM micrograph of samples (a sample C3, b sample C1) soon after the performance of corrosion tests

Fig. 22  EDAX revealing the

elemental percentage of Mo,
Cr, Nb, Ni present in corroded
sample C1

the pit formed on the grain boundary. The sample C3 clearly

shows difference from sample C1, the oxides formed appears
in bright colour at the subgrain boundaries, indicating the
absence of intergranular and overall corrosion. Considering
sample C3, not much traces of corrosion is found on the grain
boundary [39, 40]. Generally grain boundaries are located
from the arrangement on the subgrain boundary, such infer-
ences are not easily identifiable.
Thus the sample C3 found to have 0.00330 mm/yr cor-
rosion rate is obviously less compared to that of sample C1
containing 0.01157 mm/yr corrosion rate. The presence of
Cr, Mo and Ni helps in the corrosion resistance in chloride
environment and is also the reason for lesser corrosion rate in
case of sample C3.

Fig. 23  Presence of Mo-rich precipitates, NbC on sample C3

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4 Conclusion The solid solution effect in Ni–Cr matrix is contributed

by the presence of Nb and Mo. The variation of corro-
From the results obtained from the metal deposition of sion resistance depends on the dendritic arm space and
Ni–Cr-Mo alloy over 316L austenitic stainless steel using finer dendritic arm indicates more corrosion resistance.
CMT cladding process, the following were drawn:

• Defect and pores free clad beads are obtained from

cladding of Inconel 625 over 316L. The welding cur- References
rent of 180 Amps, voltage of 17 volts, torch angle of
80° and travel speed of 175 mm/min, produces minimal 1. P. Varghese, E. Vetrivendan, M.K. Dash, S. Ningshen, M.
Kamaraj, U.K. Mudali, Weld overlay coating of Inconel 617 M
dilution (9.3%) and higher clad bead width. The reason on type 316 L stainless steel by cold metal transfer process. Surf.
for minimal dilution is mainly due to the higher heat Coat. Technol. 357, 1004–1013 (2019)
input (0.918 kJ/mm) in the Inconel 625 clad region. 2. O.H. Madsen, New technologies for waste to energy plants, in
• The generic weld morphology comprising of colum- 4th International Symposium on Waste Treatment Technologies,
Babcock & Wilcox Vølund, Sheffield (2003)
nar dendritic microstructure along with fine interme- 3. T. Baldridge, G. Poling, E. Foroozmehr, R. Kovacevic, T. Metz, V.
tallic precipitates are observed in the clad region. The Kadekar, M.C. Gupta, Laser cladding of Inconel 690 on Inconel
columnar and coaxial dendrites are observed nearer to 600 superalloy for corrosion protection in nuclear applications.
clad region towards the interface, coarsened equiaxed Opt. Lasers Eng. 51(2), 180–184 (2013)
4. S. Selvi, A. Vishvaksenan, E. Rajasekar, Cold metal transfer
grains are seen along the HAZ, columnar and cellular (CMT) technology—an overview. Def. Technol. 14(1), 28–44
dendrites are observed in the region close to the fusion (2018)
boundary. 5. H.T. Zhang, J.C. Feng, P. He, B.B. Zhang, J.M. Chen, L. Wang,
• At low heat input, CMT produces small HAZ zone The arc characteristics and metal transfer behaviour of cold metal
transfer and its use in joining aluminium to zinc-coated steel.
resulting in minimal intergranular liquation in HAZ. Mater. Sci. Eng. A 499(1–2), 111–113 (2009)
This causes low amount of tensile stresses to be pro- 6. P. Kah, M. Shrestha, J. Martikainen, Trends in joining dissimilar
duced. metals by welding, in Applied Mechanics and Materials, vol. 440,
• Average microhardness indentation value of the clad, ed. by D. Yang, T. Zhang, Q. Lu (Trans Tech Publications, Zurich,
2014), pp. 269–276
interface, base are 265 ± 25 ­HV0.5, 200 ± 20 ­HV0.5 and 7. A. Schierl, The CMT process a revolution in welding technology.
190 ± 15 ­HV0.5, respectively. The increase of hardness Weld. World Lond. 49(I), 38 (2005)
is attributed mainly due to lower heat input and faster 8. C.G. Pickin, S.W. Williams, M. Lunt, Characterisation of the cold
cooling rate, therby causing a reduction the dendritic metal transfer (CMT) process and its application for low dilution
cladding. J. Mater. Process. Technol. 211(3), 496–502 (2011)
arm spacing. The presence of carbides and interme- 9. J. Feng, H. Zhang, P. He, The CMT short-circuiting metal transfer
tallics also contribute to higher hardness. In addition process and its use in thin aluminium sheets welding. Mater. Des.
the growth of columnar microstructures nearer to 30(5), 1850–1852 (2009)
the fusion boundary and the hard intermetallics also 10. M. Solecka, P. Petrzak, A. Radziszewska, The microstructure of
weld overlay Ni-base alloy deposited on carbon steel by CMT
enhance the hardness along the clad region. method, in Solid State Phenomena, vol. 231, ed. by B. Dubiel,
• The tensile property of clad area ultimately shows the T. Moskalewicz (Trans Tech Publications, Zurich, 2015), pp.
best results. The tensile strength of interface region 119–124
shows an elongation 15% higher than substrate is nota- 11. M. Rozmus-Górnikowska, M. Blicharski, J. Kusiński, Influence of
weld overlaying methods on microstructure and chemical compo-
ble. The tensile strength of clad area reaching 706 MPa, sition of Inconel 625 boiler pipe coatings. Met. Mater. 52(3), 1–7
indicates its excellent high-temperature property. (2014)
• From the fractographic results, the samples mostly 12. J. Tuominen, J. Näkki, H. Pajukoski, T. Nyyssönen, T. Ristonen,
comprises of dimpled rupture, exhibited by cup and T. Peltola, P. Vuoristo, High performance wear and corrosion
resistant coatings by novel cladding techniques. Surf. Modif.
cone-like depression, nature of fracture appears to be Technol. XXVIII, 13 (2014)
fibrous with dimpled network. The chance for the ini- 13. A. Evangeline, P. Sathiya, Cold metal arc transfer (CMT) metal
tiation of crack at the grain boundary is shown from the deposition of Inconel 625 superalloy on 316L austenitic stainless
cleavage type of fracture. The secondary precipitates steel: microstructural evaluation, corrosion and wear resistance
properties. Mater. Res. Express 6(6), 066516 (2019)
like γ′ and γ″ are the reason behind occurrence of mac- 14. A. Evangeline, S. Paulraj, Structure–property relationships of
rovoids. Inconel 625 cladding on AISI 316L substrate produced by hot
• From the results of corrosion resistance, the increase wire (HW) TIG metal deposition technique. Mater. Res. Express
is mainly due to higher amount of Mo and Cr in Ni- (2019). https​://doi.org/10.1088/2053-1591/ab350​f
15. Q.Y. Wang, Y.F. Zhang, S.L. Bai, Z.D. Liu, Microstructures,
based alloys. The formation of ­Cr2O3 and the passiva- mechanical properties and corrosion resistance of Hastelloy C22
tion action of the clad zone is due to the presence of Cr. coating produced by laser cladding. J. Alloys Compd. 553, 253–
258 (2013)

13
 Metals and Materials International

16. Y. Liang, S. Hu, J. Shen, H. Zhang, P. Wang, Geometrical and 29. R.F. Allen, N.C. Baldini, P.E. Donofrio, E.L. Gutman, E. Keefe,
microstructural characteristics of the TIG-CMT hybrid welding J.G. Kramer et al., Annual Book of ASTM Standards (ASTM, West
in 6061 aluminum alloy cladding. J. Mater. Process. Technol. 239, Conshohocken, 1998), p. 188
18–30 (2017) 30. N.V. Rao, G.M. Reddy, S. Nagarjuna, Weld overlay cladding of
17. R.A. Miller, Oxidation-based model for thermal barrier coating high strength low alloy steel with austenitic stainless steel–struc-
life. J. Am. Ceram. Soc. 67(8), 517–521 (1984) ture and properties. Mater. Des. 32(4), 2496–2506 (2011)
18. T.E. Abioye, J. Folkes, A.T. Clare, A parametric study of Inconel 31. O.T. Ola, F.E. Doern, A study of cold metal transfer clads in
625 wire laser deposition. J. Mater. Process. Technol. 213(12), nickel-base INCONEL 718 superalloy. Mater. Des. 57, 51–59
2145–2151 (2013) (2014)
19. S. Bhattacharya, G.P. Dinda, A.K. Dasgupta, J. Mazumder, Micro- 32. Y. Kaya, N. Kahraman, An investigation into the explosive weld-
structural evolution of AISI 4340 steel during direct metal deposi- ing/cladding of Grade A ship steel/AISI 316L austenitic stainless
tion process. Mater. Sci. Eng. A 528(6), 2309–2318 (2011) steel. Mater. Des. 1980–2015(52), 367–372 (2013)
20. X. Xu, G. Mi, L. Chen, L. Xiong, P. Jiang, X. Shao, C. Wang, 33. H.N. Moosavy, M.R. Aboutalebi, S.H. Seyedein, An analytical
Research on microstructures and properties of Inconel 625 coat- algorithm to predict weldability of precipitation-strengthened
ings obtained by laser cladding with wire. J. Alloys Compd. 715, nickel-base superalloys. J. Mater. Process. Technol. 212(11),
362–373 (2017) 2210–2218 (2012)
21. S. Saroj, C.K. Sahoo, M. Masanta, Microstructure and mechani- 34. C. Fink, M. Zinke, Welding of nickel-based alloy 617 using modi-
cal performance of TiC-Inconel825 composite coating deposited fied dip arc processes. Weld. World 57(3), 323–333 (2013)
on AISI 304 steel by TIG cladding process. J. Mater. Process. 35. D. Janicki, Laser cladding of Inconel 625-based composite coat-
Technol. 249, 490–501 (2017) ings reinforced by porous chromium carbide particles. Opt. Laser
22. D. Verdi, M.A. Garrido, C.J. Múnez, P. Poza, Mechanical proper- Technol. 94, 6–14 (2017)
ties of Inconel 625 laser cladded coatings: depth sensing indenta- 36. L.Y. Xu, M. Li, H.Y. Jing, Y.D. Han, Electrochemical behavior
tion analysis. Mater. Sci. Eng. A 598, 15–21 (2014) of corrosion resistance of X65/Inconel 625 welded joints. Int. J.
23. S.W. Banovic, J.N. DuPont, A.R. Marder, Dilution and micro- Electrochem. Sci. 8, 2069–2079 (2013)
segregation in dissimilar metal welds between super austenitic 37. K.Y. Chiu, F.T. Cheng, H.C. Man, Corrosion behavior of AISI
stainless steel and nickel base alloys. Sci. Technol. Weld. Join. 316L stainless steel surface-modified with NiTi. Surf. Coat. Tech-
7(6), 374–383 (2002) nol. 200(20–21), 6054–6061 (2006)
24. J.N. DuPont, A.R. Marder, M.R. Notis, C.V. Robino, Solidification 38. H.Z. Rajani, S.A. Mousavi, F.M. Sani, Comparison of corrosion
of Nb-bearing superalloys: part II. Pseudoternary solidification behavior between fusion cladded and explosive cladded Inconel
surfaces. Metall. Mater. Trans. A 29(11), 2797–2806 (1998) 625/plain carbon steel bimetal plates. Mater. Des. 43, 467–474
25. L. Shepeleva, B. Medres, W.D. Kaplan, M. Bamberger, A. (2013)
Weisheit, Laser cladding of turbine blades. Surf. Coat. Technol. 39. X. Xu, G. Mi, L. Xiong, P. Jiang, X. Shao, C. Wang, Morpholo-
125(1–3), 45–48 (2000) gies, microstructures and properties of TiC particle reinforced
26. G. Longlong, Z. Hualin, L. Shaohu, L. Yueqin, X. Xiaodong, F. Inconel 625 coatings obtained by laser cladding with wire. J.
Chunyu, Formation quality optimization and corrosion perfor- Alloys Compd. 740, 16–27 (2018)
mance of Inconel 625 weld overlay using hot wire pulsed TIG. 40. J. De Damborenea, A.J. Vázquez, B. Fernández, Laser-clad 316
Rare Met. Mater. Eng. 45(9), 2219–2226 (2016) stainless steel with Ni-Cr powder mixtures. Mater. Des. 15(1),
27. T.E. Abioye, P.K. Farayibi, D.G. McCartney, A.T. Clare, Effect 41–44 (1994)
of carbide dissolution on the corrosion performance of tungsten
carbide reinforced Inconel 625 wire laser coating. J. Mater. Pro- Publisher’s Note Springer Nature remains neutral with regard to
cess. Technol. 231, 89–99 (2016) jurisdictional claims in published maps and institutional affiliations.
28. C.C. Silva, H.C. De Miranda, M.F. Motta, J.P. Farias, C.R.M.
Afonso, A.J. Ramirez, New insight on the solidification path of
an alloy 625 weld overlay. J. Mater. Res. Technol. 2(3), 228–237
(2013)

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