JP2010024529A - Thermal spraying alloy, member provided with surface layer and method for producing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To increase the wear resistance of an Ni-B based or Co-B based self-fluxing alloy by raising its melting point. <P>SOLUTION: Regarding the method for producing a member having a surface layer, Ni-(8 to 12wt.%) B-based or Co-(8 to 12wt.%) B based self-fluxing alloy powder is mixed with a boride former element powder in 39 to 100% of B mol number, and the mixed powder is thermal-sprayed on the base member, so as to form a thermal sprayed layer, and the thermal sprayed layer is subjected to fusing. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a thermal spray alloy with improved wear resistance, a member provided with a surface layer, and a method for manufacturing the same, and more particularly to a thermal spray alloy containing boride, a member provided with a surface layer, and a method for manufacturing the same.

  Various surface treatments that improve the wear resistance and corrosion resistance of metal materials are known. Thermal spraying and overlay welding have the advantage that the thickness of the hardened layer can be increased as compared with physical vapor deposition (PVD) and chemical vapor deposition (CVD). Overlay welding, in which the substrate is melted by plasma arc, has a problem of causing cracks when the temperature is lowered. Thermal spraying such as high-speed flame spraying and plasma spraying has no problem of cracking, and the workable materials are wide such as ferrous materials, non-ferrous materials, self-fluxing alloys, ceramics, and carbides.

  The self-fluxing alloy is an alloy in which B and Si are mixed with Ni base or Co base and the melting point is lowered to, for example, about 960 ° C. to 980 ° C., and has high fluidity and is easy to apply thermal spraying. In order to improve the corrosion resistance and wear resistance, Cr, Zr, Mo, W, C and the like are further added. The thermal spray layer formed by thermal spraying is subjected to a fusing treatment that is heated and held at about 980 ° C. to 1000 ° C., for example. The sprayed layer is semi-melted to reduce pores in the sprayed layer and to make the sprayed layer uniform, thereby causing diffusion at the bonding interface and improving adhesion. The hardness of the sprayed layer of the self-fluxing alloy is HRc 60 or more. In addition to lowering the melting point of the self-fluxing alloy, the added B forms a boride with other additives such as Cr and improves the hardness. Adhesion, in-layer uniformity, and pore reduction are superior features compared to other thermal spray materials.

  Japanese Patent Application Laid-Open No. 08-31630 proposes a self-fluxing alloy material for thermal spraying that contains C, Si, Cr, Mo, Cu, Fe, Mn, and B at a predetermined weight percent, with the balance being Ni and inevitable impurities.

  Japanese Patent Application Laid-Open No. 9-13161 discloses a Co alloy powder containing 2-12 wt% of B, Mo carbide and W carbide of 10 wt% or more, and the total amount of C is 1.5 times or less of the B amount in molar ratio. It is proposed that the mixed powder blended in is sprayed on the surface of the object to be treated and then heat-treated to deposit free carbon. B in the Co alloy reacts with Mo and W to form double borides, and C is liberated and precipitates. Since all carbides do not react with borides, a lower limit for carbides and an upper limit for carbon content are specified.

  Japanese Patent Laid-Open No. 2006-161131 is a Co-based self-fluxing alloy containing Cr and C, which is produced by an atomizing method, and chromium carbide having a particle size of 5 μm or less is uniformly precipitated in Co-based self-fluxing alloy particles. A Co-based self-fluxing alloy for thermal spraying is proposed.

  Japanese Patent Application Laid-Open No. 2008-115443 proposes a Ni-based self-fluxing alloy powder for thermal spraying that contains at least Cr, C, and Co and in which chromium carbide having a particle size of 5 μm or less is uniformly deposited inside the particles.

JP 08-31630 A Japanese Patent Laid-Open No. 9-13161 JP 2006-161131 A JP, 2008-115443, A When a self-fluxing alloy member carries out friction wear, the performance can be exhibited when the temperature of the sliding contact part is low and short. When worn due to high-speed sliding speed or contact sliding in a high-temperature environment, there is a problem in that a decrease in hardness is observed due to the low melting point, and melting or seizure occurs. In order to improve the specific wear rate in the high-speed sliding part, it is important to raise the melting point of the material.

  The self-fluxing alloy has a merit that the melting point is low, but it is desired to overcome wear resistance, galling resistance, and hardness reduction at high temperatures. The decrease in melting point in the self-fluxing alloy is due to the addition of B and Si. In particular, B greatly contributes to lowering the melting point. B forms a boride and greatly contributes to properties such as hardness.

  In order to improve the specific wear rate due to wear at the high speed sliding portion, it is important to raise the melting point of the material. In Ni-B and Co-B based self-spraying alloys, if the B composition can be lowered after spraying, the melting point can be increased and the wear resistance can be improved.

  An object of the present invention is to lower the B composition dissolved in the self-fluxing alloy after spraying a Co-B or Ni-B self-fluxing alloy to increase the melting point and improve the wear resistance.

According to one aspect of the present invention,
There is provided a thermal spray alloy obtained by adding a boride-forming element having 39 to 100% of the number of B moles to a Ni- (8 to 12 wt%) B basic system or a Co- (8 to 12 wt%) B basic system.

According to another aspect of the invention,
Mixed powder obtained by mixing boride-forming element powders of 39 to 100% of B moles with Ni- (8 to 12 wt%) B basic system or Co- (8 to 12 wt%) B basic system self-fluxing alloy powder The process of preparing
Spraying the mixed powder on a base member to form a sprayed layer;
Fusing the sprayed layer;
The manufacturing method of the member provided with the surface layer containing is provided.

  A sprayed layer having excellent characteristics can be obtained by adjusting the addition amount of a boride-forming element that is easily combined with B and B added to the Co group or Ni group.

  FIG. 1A shows the phase diagram of the Ni-B alloy system. Eutectic compositions are observed at B composition of 3.6 wt%, 7.3 wt%, 10.7 wt%, and 13.2 wt%. Since the atomic weight of B is as small as 10.81 compared to the atomic weight of Ni of 58.71, atm% is a numerical value considerably larger than wt%. When the B composition is 3.6 wt%, 7.3 wt%, and 10.7 wt%, the melting points are 1090 ° C., 1125 ° C., and 1018 ° C., respectively. The melting point of Ni is 1455 ° C. and the melting point of B is 2092 ° C. However, if the B composition is 3.6-12 wt%, the melting point is 1156 ° C. or lower. Addition of Si further lowers the melting point.

  FIG. 1B shows the phase diagram of the Co—B alloy system. The B composition has a eutectic composition of 4 wt%, 10 wt%, and 22 wt%, and the melting points are 1110 ° C., 1250 ° C., and 1350 ° C. Since the atomic weight of B is as small as 10.81 compared with the atomic weight of Co. 58.93, atm% is a numerical value much larger than wt%. When the B composition is 4 wt% and 10 wt%, the melting points are 1110 ° C. and 1250 ° C., respectively. The melting points of B and Co are 2092 ° C. and 1495 ° C. shown at both ends in the figure, but if the B composition is 4 to 10 wt%, the melting point is 1280 ° C. or less. A low melting point can be realized in the vicinity of the eutectic composition. Addition of Si further lowers the melting point.

  If a sprayed layer is formed using a low melting point self-fluxing alloy, the B composition can be smaller than 3.6 wt% in the case of Ni-B alloy system, and the B composition can be smaller than 4 wt% in the case of Co-B alloy system. As the B composition decreases, the melting point increases. In order to reduce the amount of B dissolved in the Ni group and Co group, it was considered to add an element that easily combines with B.

  Thermodynamic free energy calculations have shown that W and Mo are effective. For example, when fusing by spraying a Ni—B—Cr—W self-fluxing alloy on a Fe base, it is easy to make a boride in the order of W> Fe> Cr> Ni. That is, W preferentially combines with B. This combination of W and B makes it possible to reduce the amount of B in the Ni base. The same applies to Mo. Precipitated WB (MoB) improves wear resistance. In order to disperse the amount of precipitates as finely as possible, it is preferable that the amount of B in the master alloy is larger than that of a normal self-fluxing alloy within the range in which the raw material can be manufactured.

  The self-fluxing alloy powder is manufactured by the atomizing method. Due to manufacturing problems, the upper limit of the amount of B added is 12 wt%. Therefore, the amount of B added is 8 wt% to 12 wt%. Therefore, Ni-10B (Ni mixed with 10 wt% B) was used as the basic self-fluxing alloy.

  In the case of W, the precipitated W boride is in the form of WB, and W1 mole is combined with B1 mole. The basic self-fluxing alloy powder is formed by an atomizing method. Since W has a high melting point, W powder is prepared separately. An experiment was conducted in which W powder was mixed at various mixing ratios with Ni-10B basic alloy powder, the mixed powder was sprayed, and the sprayed layer was fused. It can be seen that when W is added in an extremely smaller number of moles than the number of moles of added B, surplus B generates Fe and boride of the base material during fusing, becomes coarse, and the hardness becomes as low as about HRc 50 to 55. It was. When W reacts with the corresponding part of B, if fusing after spraying is optimized, the hardness is equal to or higher than that of conventional self-fluxing alloys, and characteristics with excellent wear resistance and anti-galling properties may appear. understood. It is considered that excellent characteristics cannot be obtained with a W amount in which a large amount of surplus B remains in the sprayed layer.

  As a result of various experiments, Ni-10B-12Cr-5Si was set as the self-fluxing alloy for thermal spraying, and plasma spraying and fusing were performed by changing the mixing ratio of the self-fluxing alloy powder for thermal spraying and the W powder. In samples S1-S6, the weight ratio of the self-fluxing alloy for thermal spraying to W is S1 (100: 0), S2 (92: 8), S3 (87:13), S4 (64:36), S5 (60: 40) and S6 (38:62). As Comparative Example C, a normal self-fluxing alloy, Ni-3.5B-17Cr-4Si, was also plasma sprayed. The hardness HRc of the thermal sprayed layer sample subjected to the fusing treatment was measured, and the specific wear amount was further measured by the Ogoshi type abrasion test.

  FIG. 2A shows an outline of the Ogoshi type abrasion test. From above the test piece Sp, the ring is pressed with a load w, the ring is rotated, and the sliding distance L is rubbed at a predetermined friction speed. The test was performed in a dry state without using a lubricant. The friction speed was set at a high speed of 2.4 m / sec. Let V be the volume dug into the specimen. S = V / w · L is the specific wear amount. The smaller the specific wear amount, the higher the wear resistance.

FIG. 2B is a table summarizing the values of hardness HRc and specific wear of each sample obtained by measurement. The hardness of Comparative Example C will be considered based on the hardness of 55-60 and the specific wear amount of 2.0E-07 (2.0 × 10 ⁻⁷ ) mm ² / kgf. The sample S1 without addition of W has the same hardness as the comparative example, and the specific wear amount is improved by about one digit. In the samples S2 and S3 having the W composition of 8 wt% and 13 wt%, the hardness is lower than that of the comparative example. The specific wear amount is smaller than that of the comparative example, but larger than the sample S1 without addition of W. Sample S4 having a W composition of 36 wt% shows higher hardness and lower specific wear than sample S3. However, the hardness is lower and the specific wear amount is larger than that of the sample S1 without W addition. In the samples S2, S3, and S4, the merit by adding W is not obtained.

  Sample S5 having a W composition of 40 wt% showed a hardness of 63.8 and a lower specific wear rate of 9.46E-9 than sample S1 without W addition. Sample S6 having a W composition of 62 wt% showed a higher hardness of 64.0 and a lower specific wear amount of 8.10E-9.

  In sample S6, assuming that the total amount of self-fluxing alloy powder and W powder is 100 g, (Ni-10B-12Cr-5Si) is 38 g, inner B is 3.8 g, and W is 62 g. In terms of the number of moles, B is 0.35 mol and W is 0.34 mol, which is almost equimolar. When the W1 atom combines with the B1 atom, almost all B dissolved in the Ni group combines to become WB. Since the B composition is greatly reduced, it is considered that the melting point is also increased. In sample S5, assuming that the total amount of self-fluxing alloy powder and W powder is 100 g, (Ni-10B-12Cr-5Si) is 60 g, inner B is 6.0 g, and W is 40 g. The number of moles of W is about 39% of the number of moles of B.

  Although the characteristics of sample S5 do not reach the characteristics of sample S6, the hardness is as high as 63.8 and the specific wear amount is as low as 9.46E-9. Sample S4 corresponds to 36 g of W with respect to 6.4 g of B, and the number of moles of W is about 33% of the number of moles of B. Sample S4 does not show an improvement in performance compared to sample S1 without W addition. From these experimental results, it is preferable that the number of moles of W added is about 39% to 100% of the number of moles of B.

  FIG. 3 shows an observation image of the sample S6 with a scanning secondary electron microscope. There was no galling tendency. It is thought that the melting point has increased and the galling property has improved.

In a Ni-based B-containing alloy manufactured by a thermal spraying process, a mixed powder raw material is prepared by increasing the amount of B and adding W in a mole number of 39% to 100% of the mole number of B, creating a sprayed layer by spraying, It has been found that by fusing, W and B are reacted to precipitate WB, and the B concentration in the Ni base is lowered to raise the melting point to obtain good wear resistance in a high sliding speed range. . Since the amount of B solid solution in the Ni group decreases, the intermetallic compound Ni ₃ B between Ni and B does not exist, and a hardened layer having a form in which WB particles exist in tough Ni is formed. It is done.

  It was also found that when the additive element is W, a good sprayed layer cannot be obtained unless the spraying conditions are set appropriately. 38 (Ni-10B-12Cr-5Si) · 62W will be described as an example.

  FIG. 4 shows experimental results in which the particle diameters of the W powder and Ni-10B-12Cr-5Si (abbreviated as Ni-10B) powder and the plasma conditions are variously changed. Samples S11 to S18 were prepared by changing the conditions.

In sample S11, the particle size of the W powder used for thermal spraying was 75 μm to 150 μm. The particle size of the Ni-10B powder was 63 μm to 125 μm. The plasma conditions were standard conditions. That is,
Powder carrier gas Ar flow rate: 99 SCFH (cubic feet per standard state time),
H ₂ flow rate for heat supply: 15 SCFH,
Current: 500A
Voltage: 65V,
Carrier gas flow rate: 18.5 SCFH,
Met.

  In sample S11, although W powder was sprayed, there was no W in the sprayed layer. In addition, pores were formed in the sprayed layer. It was considered that the particle size of the W powder was large and repelled by the base material, leaving no W powder in the sprayed layer. As a countermeasure, the particle size of the W powder was lowered to 40 μm or less. In the material used, the particle size of the W powder was 5 μm to 40 μm. The following samples use this W powder.

  In sample S12, W powder having a particle size of 40 μm or less was used. Other conditions are the same as those of the sample S11. W entered the sprayed layer. In order to incorporate the W powder into the sprayed layer, it has been found effective to reduce the particle size of the W powder. However, pores are generated.

In sample S13, the amount of heat generated was increased by increasing the H ₂ flow rate to 26 SCFH. The voltage was lowered slightly to 60 V, and the carrier gas flow rate was reduced to 13.5 SCFH. Like sample S12, W entered, but the pores did not escape.

In sample S14, the particle size of Ni-10B powder was reduced to 32 μm to 63 μm, the carrier gas Ar flow rate of the powder was increased to 175 SCFH, and the powder was blown strongly, and the H ₂ flow rate was lowered to 11 SCFH to lower the heat quantity. . The voltage was 66 V and the carrier gas flow rate was 13.5 SCFH. At this time, W did not enter and the pores did not escape.

In sample S16, the powder carrier gas Ar flow rate was 116 SCFH, the H ₂ flow rate was lowered to 9.5 SCFH, the heat amount was lowered, the current was lowered to 400 A, and the voltage was 63 V to weaken the plasma. The carrier gas flow rate was 13.5 SCFH. Other conditions are the same as those of the sample S12. W did not enter and the pores did not escape. If the plasma energy is insufficient, W particle uptake does not seem to work.

In sample S15, the particle size of the Ni-10B powder is returned to 63 μm to 125 μm, the H ₂ flow rate is increased to 20 SCFH to increase the amount of heat, the powder carrier gas Ar flow rate is further increased to 212 SCFH, and the voltage is increased to 80V. The carrier gas flow rate was increased to 20.5 SCFH. W entered, but the pores did not escape.

  In sample S17, the particle size of the Ni-10B powder was reduced to 32 μm to 63 μm. Other conditions are the same as those of the sample S12. W entered and the pores escaped. It is a satisfactory result.

  In sample S18, the particle size of the Ni-10B powder was changed to 63 μm to 90 μm. Other conditions are the same as in sample S17. H entered and pores escaped. It is a satisfactory result.

From the above results, it is considered that it is difficult to insert W and remove pores unless the particle size of the W powder and the particle size of the Ni-10B powder are appropriately set. The particle size of W is preferably 40 μm or less, and in the actual material, it was 5 μm to 40 μm. In particular, the experimental results of W powder having an average particle diameter of 14.5 μm were excellent. The particle size of the Ni-10B powder may be 32 μm to 90 μm. Furthermore, if the plasma conditions are not set appropriately, it is considered difficult to insert W and remove pores. For example, the H ₂ flow rate is preferably 15 SCFH or more.

  The case where the surface layer is formed by mixing and spraying Ni-10B alloy powder and W powder has been described above. Using the Co-10B alloy powder and W powder, the formation of borides could be confirmed. Similar results are expected when using Co-10B alloy powder and W powder.

  The same phenomenon is expected to occur when Mo is used instead of W.

  As mentioned above, although this invention was demonstrated along the Example, this invention is not limited to this. For example, a spraying method other than plasma spraying may be used. It will be apparent to those skilled in the art that various modifications, substitutions, combinations, improvements, and the like can be made.

1A and 1B are phase diagrams of a Ni-B binary system and a Co-B binary system. FIG. 2A is a schematic cross-sectional view for explaining the Ogoshi type wear test, and FIG. 2B is a table summarizing the measurement results of hardness and specific wear amount measured for the sample. FIG. 3 is a photograph of an observation image of the worn surface of sample S6 with a scanning secondary electron microscope. FIG. 4 is a table summarizing manufacturing process examples for the sample S6.

Claims (11)

  A sprayed alloy obtained by adding a boride-forming element having 39 to 100% of the number of moles of B to a self-fluxing alloy of Ni- (8 to 12 wt%) B basic system or Co- (8 to 12 wt%) B basic system.   The thermal spray alloy according to claim 1, wherein the boride-forming element is W or Mo.   The thermal spray alloy according to claim 2, wherein the self-fluxing alloy is a Ni- (8 to 10 wt%) B basic system and the boride-forming element is W.   Furthermore, the thermal spray alloy of any one of Claims 1-3 which added Si and Cr.   The thermal spray alloy according to claim 4, wherein the self-fluxing alloy is Ni- (8-10) B-12Cr-5Si. A base member having a surface that requires wear resistance;
A surface layer formed on the surface, the surface layer formed of the thermal spray alloy according to any one of claims 1 to 5 and including a large number of precipitation regions in which borides are finely precipitated;
A member provided with a surface layer. Mixed powder obtained by mixing boride-forming element powders of 39 to 100% of B moles with Ni- (8 to 12 wt%) B basic system or Co- (8 to 12 wt%) B basic system self-fluxing alloy powder The process of preparing
Spraying the mixed powder on a base member to form a sprayed layer;
Fusing the sprayed layer;
The manufacturing method of the member provided with the surface layer containing.   The method for producing a member having a surface layer according to claim 7, wherein the boride-forming element is W or Mo.   9. The surface according to claim 8, wherein the self-fluxing alloy powder is a Ni- (8-10 wt%) B basic powder having a particle size of 32-63 [mu] m, and the boride-forming element powder is a W powder having a particle size of 40 [mu] m or less. The manufacturing method of the member provided with the layer.   The manufacturing method of the member provided with the surface layer of any one of Claims 7-9 in which the process of forming the said sprayed layer performs plasma spraying. The method for producing a member having a surface layer according to claim 10, wherein the plasma spraying uses Ar / H ₂ mixed plasma and the H ₂ gas flow rate is 15 SCFH or more.