JPS6342362A - Production of surface coated steel material - Google Patents

Abstract

PURPOSE:To easily produce a strong and durable surface coated steel material by bombarding a steel base material having a nitride layer formed on the surface with metal ions and by forming a coating layer of the nitride of a group IVa element by ion plating. CONSTITUTION:A steel base material (structural steel, spring steel, stainless steel or the like) having a nitride, carbide or carbonitride layer formed on the surface as usual is bombarded with ions of a metal such as a group IVa or Va element of the periodic table by arc discharge. The bombardment is preferably carried out at about 100-2,000V voltage in a high vacuum. A coating layer of one or more kinds of compounds selected among the nitrides, carbides and carbonitrides of the group IVa and Va elements is then formed on the steel base material by ion plating at about 50-700V voltage under about 10<-3>-10Torr pressure. The pref. thickness of the coating layer is about 0.1-10mum.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention relates to a method for manufacturing a surface-coated steel material provided with a hard coating layer.

(Conventional technology) As a method for modifying the surface of steel materials such as tools and molds,
A surface hardening method in which the surface of a steel material is hardened by forming a nitrided layer, a carbonized layer, or a carbonitrided layer (hereinafter referred to as a hardened surface layer) on the surface, and a hard coating is formed on the surface of the steel material by a PVD method or a CVD method. There is a way. However, when a hard coating is formed on the surface, these coatings are brittle and are likely to peel off, and once such peeling occurs, there is a problem in that the wear of the soft underlying layer progresses. Therefore,
As a solution to this problem, a combination of these surface modification methods, that is, a method in which a hard coating is formed on the surface of the steel material after the surface of the steel material is hardened, is proposed in JP-A-58-64377. In this method, a tool base material of high-speed tool steel or alloy tool steel is held in a vacuum container and a nitrided or carbonitrided layer is formed on its surface by glow discharge. IVa is deposited on the nitride layer or carbonitride layer by ion plating.
This is a method for manufacturing a surface-coated tool, characterized by forming a coating layer of one or more types of carbides, nitrides, and carbonitrides of group elements or Va group elements.

(Problems to be Solved by the Invention) However, in the method described in JP-A-58-64377, the surface hardening method uses glow discharge;
That is, a surface hardening method using ions is used, but the equipment used for this method is not widely used, and the maintenance and operation costs are high. On the other hand, the equipment used for other known surface hardening methods, such as the method using gas or the method using molten salt, is widely used and the technology has matured, making it inexpensive to use. The method has the disadvantage that these surface hardening methods cannot be utilized.

In addition, in this method, the surface of the steel material subjected to surface hardening treatment must be consistently shielded from the atmosphere to prevent it from being contaminated by oxide film and other substances. must be done in a way that forms the For this reason, the gas system introduced into the equipment becomes complicated.
Another disadvantage is that the operation is complicated.

In addition, -a, many types of phases are generated when steel materials are treated by the surface hardening method, and some of these phases may cause peeling of the coating layer later formed by ion plating. Doesn't even exist. For example, in nitriding treatment, a nitrogen diffusion layer is generated near the surface, but further near the surface, a compound phase of iron and nitrogen called the ε phase is generated, and furthermore, a porous layer is generated on the outermost surface. This porous layer is easily oxidized when exposed to the atmosphere, resulting in a blackened film. Even if a hard film is formed by ion plating on a surface where compounds such as the ε phase or blackened film are present, peeling is likely to occur. Although the formation of a blackened film can be prevented by blocking air, it is difficult to remove the ε phase. Therefore, even if the ion plating method is performed directly on the base material while it is shielded from the atmosphere after being treated by the surface hardening method, there is a problem that many defective products will be produced.

Therefore, an object of the present invention is to form a durable and robust hard coating layer on the hardened surface layer by ion plating, which is applicable to the hardened surface layer formed by any method. The object of the present invention is to provide a method for manufacturing surface-coated steel materials that can be used to produce surface-coated steel materials.

(Means for Solving the Problems) As a means for solving the above-mentioned problems, the present invention bombards a steel base material with a nitrided layer, a carbonized layer, or a carbonitrided layer on its surface with metal ions, and then A nitrided layer, a carbonized layer, which has been subjected to the bombardment treatment, is formed by an ion plating method using one or more types of coating layer selected from nitrides, carbides, and carbonitrides of elements of group TVaVa and group Va of the periodic table. The present invention provides a method for manufacturing a surface-coated steel material, which comprises forming a surface coated steel material on a layer or a carbonitrided layer.

Examples of the steel base material used in the method of the present invention include structural steel, spring steel, bearing steel, tool steel, and stainless steel.

The method for forming a hardened surface layer such as a nitrided layer, a carbonized layer, or a carbonitrided layer on the surface of the base material is not particularly limited, and may be any known surface hardening method,
That is, any method using molten salt, gas, or ions may be used. The method using molten salt is generally called salt bath nitriding method, and XCN
, XCN0. The workpiece is immersed in a molten bath of a compound represented by XZCO:1 (where X is an alkali metal), and the carbon and nitrogen produced by the decomposition of these compounds are diffused into the workpiece. . The method using gas is -g
This is called gas nitriding and carburizing or gas soft nitriding and carburizing, in which the material to be treated is placed in a gas phase of NHff, CO, etc. and heated, and the carbon and nitrogen produced by thermal decomposition of these gases are removed from the material. It is meant to spread to.

The method using ions is called ion nitriding or carburizing of -C, in which a DC voltage is applied between the object to be treated and the wall of the equipment container in NH-x or hydrocarbon gas to cause glow discharge. This is a method in which the gas is decomposed and ionized, and the resulting carbon or nitrogen ions collide with the object to be processed using an electric field.

When the base material on which the surface hardened layer is formed is subjected to the next bombardment treatment, there is no particular need to shield the base material from the atmosphere. Therefore, of course, after forming a hardened layer on the surface of the base material, it can be directly subjected to the next process in the same reaction vessel, but it is also possible to once take it out from the reaction vessel into the atmosphere and then subject it to the next process. When the surface hardening layer is formed by a method using a molten salt or a method using a gas, it is usually unavoidable that the layer is exposed to the atmosphere when moving to the next step, but there is no problem.

Next, it is preferable that the ion bombardment treatment and the ion plating be carried out continuously in the same apparatus, and any known ion plating apparatus can be used. The configuration of the ion plating device is
Generally, it consists of means for vaporizing the metal, means for ionizing the vaporized metal, means for accelerating the ionized metal by an electric field, and means for introducing a reactive gas.

The bombardment treatment using metal ions in the present invention is performed as a pretreatment for the next ion plating, and involves evaporating, ionizing, and accelerating the metal, and causing high-energy metal ions to collide with the surface of the hardened layer. It is a process. Examples of metals used in the ion bombardment process include metals from the periodic table IV used in the next process.
Group A and Va group elements, Fe, Cr, Ni, G
Examples include o.

These can be used alone or in combination of two or more.

There are no particular restrictions on the method of one shot and ionization of the metal, and the method of evaporating the metal may be any known resistance heating or electron gun heating provided in the ion plating apparatus, and the ionization of the evaporated metal may also be performed using any known method. Any method such as arc discharge, glow discharge, high frequency discharge, a method using an ionizing electrode, or a hollow cathode method may be used. Here, in particular, the arc discharge type ion plating method is a method that simultaneously evaporates and ionizes metal, and has a higher metal ionization efficiency than other methods, so it is suitable for the ion bombardment treatment of the present invention. The desired effect can be achieved in about 10 minutes.

The voltage value of the electric field for accelerating the ionized metal is preferably 100V to 2000V, particularly preferably 200V to 1500V.

The atmosphere during bombardment treatment with metal ions is, in principle, carried out under a high vacuum without using any atmospheric gas.
Depending on the case, it may be carried out under an atmospheric gas pressure of 10-' Torr to 10 Torr. The types of these atmospheric gases are He+ Ne+ Ar+ NZ+H2
Alternatively, hydrocarbons may be used, and a mixed gas of two or more of these gases may be used. When these atmospheric gases are used, the gas ions are also ionized by the glow discharge caused by the accelerating electric field and collide with the surface of the hardened layer together with the metal ions, but the essential effect of the bombardment treatment according to the present invention is due to the bombardment treatment using metal ions. .

Next, group IVa i.e. Ti, Zr, Hf and V
A coating layer of one or more types of carbides, nitrides, and carbonitrides of Group A, that is, V, Nb, and Ta, is formed on the surface after the ion bombardment treatment by an ion plating method. This ion plating method is a well-known method, and the method of vaporizing the metal and the method of ionizing the vaporized metal may be the same as that described in the ion bombardment process, but other ionized metals may be accelerated. The method of applying reactive gas and the method of using four reactive gases are different from the method in the ion bombardment process described above. That is, the voltage value of the electric field for accelerating the ionized metal is preferably 50V to 700V, more preferably 100V to 500V. Reactive gases include reactive gases for generating carbides and nitrides in the ion plating method, i.e., N, N,
H, hydrocarbons or organic compounds containing carbon and nitrogen, such as (Ctll)J. The pressure of the reactive gas varies depending on the type of reactive gas used, but
Generally, it can be carried out at a pressure of 10-3 to 1 QTorr.

The thickness of the hard coating layer formed by the ion plating method is preferably 0.1 to 10 μm, and usually 1 to 5 μm.
It should be formed as follows.

[Effect]

By forming a hardened surface layer such as a nitrided layer, a carbonized layer, or a carbonitrided layer on the surface of the steel base material using a surface hardening method, and then bringing these layers into contact with the atmosphere, a , other compounds (for example, the above-mentioned ε phase consisting of iron and nitrogen) and oxides are formed which are composed of the base metal component and carbon and/or nitrogen. According to the method of the invention,
Through ion bombardment treatment with metal ions,
It is thought that the surface hardening layer is sputtered and the by-produced compounds such as ε phase and oxides and oxides are removed, and the adverse effects caused by these are eliminated. In addition, through bombardment treatment, metal ions with high kinetic energy collide with the workpiece, and the metal ions are driven into the workpiece, forming a hard coating formed by ion plating in the subsequent process. It is thought that this improves the adhesion due to the anchor effect. In addition, when high-energy metal ions collide with the workpiece, kinetic energy is converted into thermal energy, which reheats the diffusion layer created by the surface hardening treatment in the previous process, spreading it deeper into the surface. It is estimated that this will expand the nearby high hardness region.

〔Example〕

The present invention will be explained below using examples.

Example A cylindrical member (sample 1) made of high-speed tool steel 5KH-51 (JIS G 4403) and having a diameter of 25 m+n and a length of 50 mm was treated in an ion nitriding apparatus at a temperature of 570°.
C, ion nitriding was performed under the conditions of gas composition N2/l+2=1 and total pressure of 6 Torr (Sample 2). When taken out of the device into the atmosphere, the surface of the member was covered with a blackened film.

When the cross section of this sample 2 was observed with an optical microscope, the presence of ε phase (8) was observed under the extremely thin blackened film on the outermost surface, as shown in the micrograph (x 800) shown in Figure 2. ε consisting of Fe2N, Fe, and N was determined by X-ray diffraction.
phase was confirmed).

Sample 2 on which the nitrided layer was formed was then subjected to arc discharge by applying a voltage of about 30 V between the titanium metal cathode and the anode on the chamber wall under a vacuum of 10-' Torr using an arc discharge type ion plating device. This caused evaporation and ionization of titanium at minute points on the titanium surface of the cathode. The current flowing due to the discharge at this time was about 5OA. Next, the bias voltage was set to 1000 V, and bombardment treatment with titanium ions was performed for 2 minutes. Furthermore, the bias voltage was lowered to 400V, nitrogen was introduced as a reactive gas at 10-'' Torr, and the coating of titanium nitride was coated with a thickness of 2 μm, while keeping the release of titanium evaporated under the same conditions as in the previous bombardment process. (Sample 3).

Even though sample 2 before bombardment treatment was covered with a blackened film, a uniform titanium nitride coating without peeling was obtained. When the cross section of sample 3 coated with the titanium nitride layer was observed in the same manner as described above, it was found that the titanium nitride coating (B
) The presence of ε phase and blackened film was not observed under (
The absence of an ε phase and the TiN coating were confirmed by X-ray diffraction).

For samples 1.2 and 3 used in the example, a load of 25
The Vickers hardness in g was measured. Table 1 shows the results.

Table 1 Comparative Example 1 The blackened film formed on the surface of Sample 2 in Example was removed by puff polishing. A separate cross-sectional observation of this sample revealed that the blackened film had been removed, but the presence of the ε phase was observed.

The sample from which the blackened film had been removed after nitriding was bombarded with gas ions at a bias voltage of 100V in an arc discharge type ion plating device, with the titanium evaporation source not ignited, and with a meter gas of 10 mm. After 10 minutes of treatment, a titanium nitride coating was performed in the same manner as in the example, but peeling occurred in the coating after treatment.The presence of an ε phase was observed in this sample.

Comparative Example 2 Sample 1 in Example was placed in an arc discharge type ion plating apparatus, and ion nitriding was performed under the same conditions as in Example. After that, the container was continuously evacuated without taking out the sample, and bombardment treatment with Ar gas ions was performed in the same manner as in Comparative Example 1. After that, titanium nitride coating was performed in the same manner as in the example, but the coating after treatment was Peeling was observed. In this sample, no porous layer was observed in the peeled part, but an ε phase was observed in cross-sectional microstructural observation.

〔Effect of the invention〕

According to the present invention, the surface hardening effect of the nitriding, carbonitriding, or carbonitriding of the surface of the steel base material and the effect of the hard coating layer made of nitride, carbide, or carbonitride of rVa group or Va group elements are effectively combined. As a result, a robust and durable surface-coated steel material can be produced. Furthermore, in the method of the present invention, it is not necessary to perform the surface hardening process of nitriding, carbonitriding, or carbonitriding, and the subsequent ion bombardment treatment and ion plating in the same reactor, thereby avoiding the complexity of the equipment used. This is advantageous in terms of simplifying the work.

[Brief explanation of drawings]

FIG. 1 is an optical micrograph (X800) of a cross section of a member whose surface is coated with a titanium nitride coating layer by the method of the present invention. FIG. 2 is an optical micrograph (x800) of a cross section of a member whose surface was taken out into a flame after ion nitriding. Agent Patent Attorney Zhou Iwamiya Procedure Neho (Method) RT 17, 1985 1, Indication of the case 1984 Patent side No. 184678 2, Name of the invention Method for manufacturing surface coated steel materials 3, Amendment Relationship with the case of a person who does ．． Contents of the amendment (“touch” in the third line of page 7 of the specification is corrected to “touch”.
"A cross section of a member" is corrected to "a cross section of the member showing the metallographic structure of the surface portion of the member."

Claims (1)

[Claims] A steel base material with a nitrided, carbonized, or carbonitrided layer formed on its surface is bombarded with metal ions, and then
A nitrided layer or a carbonized layer in which one or more types of coating layers selected from nitrides, carbides, and carbonitrides of group IVa elements and group Va elements of the periodic table are subjected to the bombardment treatment using an ion plating method. Alternatively, a method for producing a surface-coated steel material comprising forming the coating on a carbonitrided layer.