JPS61231151A - Surface hardening treatment for titanium or titanium alloy - Google Patents

Abstract

PURPOSE:To form a wear resisting surface hardening layer excelling in adhesion without adversely affecting the CONSTITUTION:The hardening matter consisting of >=1 kind among metallic oxides, metallic nitrides, metallic carbides, hard.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention relates to a surface hardening treatment method for titanium or titanium alloys, and in particular for the surface hardening of mechanical structural parts made of titanium or titanium alloys (hereinafter referred to as titanium alloys). This article relates to a technology that improves its wear resistance by subjecting it to hardening treatment.

[Conventional technology]

Titanium alloys are lightweight and have a high level of mechanical strength, and also have excellent corrosion resistance and brazing properties, so they have been put into practical use as high-grade parts for EA machine structures. However, since titanium alloys have lower surface hardness and lack wear resistance than cemented carbide and the like, many methods have been proposed to improve wear resistance, such as those described below.

υChromium plating method 2) Hardfacing welding method 3) Surface nitriding method 4) Carburizing method 5) Surface oxidation method hard alloy thermal spraying method υBrazing is legal 8) Hard alloy cladding method However, each of these methods has the following drawbacks.

In method υ, the titanium alloy absorbs hydrogen during the plating process, causing hydrogen embrittlement and deteriorating fatigue strength.

In method 2), the energy density during hardfacing welding cannot be sufficiently increased, and it is virtually impossible to build up welding of high melting point compounds such as carbides, so Hv: 1
It is not possible to obtain a surface hardness of 0.000 or more, and furthermore, the thermal deformation of the titanium alloy base material is significant.

The hardening depth obtained by methods 3), 4), and 5) is at most about 50 μm, and from a practical standpoint, a hardening depth sufficient to ensure sufficient wear resistance cannot be obtained.

In the methods 6) and 7), the adhesiveness between the cured layer and the base material is poor, and the cured layer is likely to peel off.

In the case of method 8), titanium alloy has a strong affinity for oxygen and is likely to form an oxide film on its surface.

It is difficult to sufficiently increase the adhesion with the cladding material.

[Problem that the invention seeks to solve]

The present invention solves the problems of the prior art as described above, and creates a hardened surface layer that not only has sufficient hardness and hardening depth but also has excellent adhesion to the titanium alloy base material, and also has the physical properties of the base material. The purpose of the present invention is to provide a technique that can be formed at any surface location where abrasion resistance is required for mechanical structural parts while minimizing adverse effects on the surface of the machine.

[Means for solving problems]

The structure of the surface hardening treatment method according to the present invention is that a hard compound consisting of a metal oxide, a metal nitride, a metal carbide, a hard intermetallic compound, a hardenable alloy element, etc. is applied to the surface of a mechanical structural part made of titanium or a titanium alloy. The gist is that the hardened material and titanium or titanium alloy are fused and integrated in the surface layer by applying a high-energy beam to the attached portion.

[Effect]

According to the present invention, as described above, a hardening substance is attached to the surface of a titanium alloy base material, and the attached portion is irradiated with a high-energy beam such as a laser beam or an electron beam, and the hardening substance is applied to the surface of the titanium alloy base material. It is heated together with the alloy to fuse and integrate it, forming an ultra-hard layer on the surface layer. The structure of the hard surface layer 1 thus obtained seems to vary depending on the type of hardening material, but typical examples include the structures shown in FIGS. 1 to 3.

Figure 1 is a T schematic diagram showing the vertical cross-sectional structure of a hardened surface area obtained when a hardened material that is easily alloyed with a titanium alloy is used, and B in the figure is an alloyed layer of the hardened material and titanium alloy. (Superhard alloy layer), D indicates a titanium alloy base material. That is, when a hardened substance that is easily alloyed with a titanium alloy is used, an ultra-hard alloy layer is formed on the surface layer of the titanium alloy base material by fusion and integration using a laser beam or the like. The thickness of the ultra-hard alloy layer B can be arbitrarily controlled by adjusting the heating depth with a laser beam, etc., and its hardness can be freely controlled by adjusting the amount of hardening material attached. I can do T.

FIG. 2 is a schematic vertical cross-sectional view of a surface hardened portion formed when a part of the hardened substance is easily alloyed with a titanium alloy. In the figure, A is a superhard material layer, which is formed by once melting a hardening material attached to the surface of a base material with a high-energy beam and then rapidly solidifying it. That is, since the hardening material is a material that is harder than itself as described above or as will be described in detail later, its own rapidly solidified layer sufficiently functions as a high-quality ultra-hard surface layer. B indicates a super hard alloy layer in which a part of the hardened substance is alloyed with a titanium alloy,
In this, a part of the hardening substance C is dispersed and alloyed in the matrix metal. This super-hard alloy layer B also plays a role in increasing the adhesion between the super-hard material 11JA and the titanium alloy base material. These cemented carbide layer A and cemented carbide 6m
The respective wall thicknesses can also be arbitrarily changed by adjusting the high-energy beam irradiation conditions and the amount of hardening material deposited.

FIG. 3 is a schematic vertical cross-sectional view of a surface hardened area obtained when using a hardening material that is relatively difficult to alloy with a titanium alloy. An ultra-hard mixed layer E, in which an ultra-hard hardening substance C is uniformly and densely dispersed in IJx, is formed on the surface of the titanium alloy base material. In other words, even if it is difficult for the hardened substance to form an alloy with the titanium alloy, the hardened substance C becomes fine crystals in the titanium alloy during the quenching stage after fusion and integration using a high-energy beam. Since T is uniformly precipitated over the entire fusion layer, the hardness of the surface layer is greatly increased, and the toughness of the surface layer is also significantly improved due to the microstructure created by rapid solidification.

In order to form the above-mentioned surface hardening layer, it is necessary to melt the hardening substance (super hard and generally has a very high melting point) attached to the surface of the base material together with the titanium alloy on the surface layer of the base material. Moreover, it does not have much thermal influence (thermal deterioration, thermal distortion, etc.) on the base material itself, and Saraban ζ is suitable for obtaining the smoothest possible hardened surface when considering the surface finishing after hardening treatment. The heat source that can meet these demands is a high-energy beam such as a laser beam or an electron beam.However, these high-energy beams have a very high concentration. Moreover, by adjusting the focal length, the energy can be concentrated at any one point.Therefore, this beam.

By scanning along the surface layer of the titanium alloy base material, rather than concentrating it on a single point on the surface layer of the titanium alloy base material to which the hardening substance has adhered, only the surface layer can be partially melted without much heat affecting the deeper parts. can be done. Moreover, with this heating method, not only can the melting depth and unification depth be freely controlled by adjusting the focal length, but also by setting the scanning area of the beam in advance. It is also possible to enjoy the advantage of being able to carry out a method of making only an arbitrary surface position of the titanium alloy base material ultrahard.

The titanium alloy used in the present invention is a lightweight, high-strength alloy whose main constituent element is titanium.
There are various types of alloying elements depending on the required properties depending on the application, but the preferred ones for improving physical properties such as strength and toughness are aluminum, molybdenum, vanadium, zirconium, aluminum, zinc, rf, iron, manganese, silicon.

Examples include Niobinen Tsum and the like, and these can be used alone or in combination of two or more kinds. More specific titanium alloys containing the above alloying elements include 1-5AI-4V, T
i-15Mo-5zr-3AI.

r;-15M0-5Zr, Ti-5A, 1-2-5s
n.

Ti-5AI-2Cr-IFe, Ti-1
3AI-IM.

-1V etc. are mentioned. Further, as described above, pure titanium can be the object of surface hardening in the present invention.

Next, the hardening substance attached to the surface of the titanium alloy is %Alρ1. Crρ3. ZrO,,SiO,,Ti
O.

Two etc. (7) Gold I [(F, material, VC, TiC, WC
, NbC.

CrC, 3, Mo, C, HfC, SiC, Tic
Metal carbides such as BN, TiN, Cr, N, NbN, Z
rN, Mo, N, HEN, nitrides such as TaN, TiB,
,VB,,CrB,,ZrB,,Mo,S i.

Hard intermetallic compounds such as N i Ti, Mo, W, Nb
, Ni.

Fe, AI, Zr, Cr, Ta, Sn, C, B
, N, O, and other hardenable alloying elements. In the present invention, one type or a mixture of two or more of these hardening substances is attached to the surface position of the titanium alloy member to be hardened,
Hardening is performed in the same manner as described above. The method for applying the hardening substance is not particularly limited, but the most common method is to disperse a finely powdered hardening substance in a paint vehicle and apply it.

〔Example〕

Al: 6.25%, V: 4.45%, ys part: T t
Titanium alloy plate (8 pieces thick) consisting of and inevitable impurities
A fine powder of the hardening substance shown in Table 1 is uniformly dispersed in a paint vehicle on the surface of the paint, and after drying, the surface layer is ultra-hardened by irradiating it with a laser beam under the conditions shown in Table 1. I did it. When the surface hardness, hardening depth, and cross-sectional structure of the hardened portion of each of the obtained ultrahardened products were investigated, the results shown in Table 1 were obtained. The Ti-5AI-
The surface hardness of 4v was Hv420.

As is clear from Table 1, by appropriately adjusting the laser beam irradiation conditions, the surface hardness of titanium alloy can be increased to H.
It can be increased to more than V100O. Further, in all cases, almost no thermal deterioration or thermal deformation of the titanium alloy itself was observed, and the surface after the hardening treatment was smooth and free of irregularities.

〔Effect of the invention〕

The present invention is constructed as described above, and its effects can be summarized as follows.

(1) The surface of titanium or titanium alloy can be easily made superhard, and its wear resistance can be dramatically improved.

(2) By adjusting the focal length of the high-energy beam, the hardened layer can be made sufficiently thick, and the adhesion between the hardened layer and the titanium alloy base material is also extremely good.

(3) Since only the surface layer can be heated with a highly focused high-energy beam, the titanium alloy base material will not undergo thermal deterioration or thermal strain.

(4) By changing the amount of hardening material attached.

Any desired surface hardness can be obtained.

(5) It is easy to operate because it only involves attaching a hardening substance to the surface of the titanium alloy member to be hardened and irradiating it with a high-energy beam, and it can be easily applied to any shape. It is also possible to easily make only a part of the titanium alloy member super hard.

[Brief explanation of drawings]

1 to 3 are schematic diagrams showing the cross-sectional structure of the ultra-hardened portion obtained by the present invention. A...Superhard material layer B...Superhard alloy metal C...Hardening substance D...Titanium alloy base material

Claims (2)

[Claims] (1) A hardening substance is attached to the surface of a mechanical structural part made of titanium or a titanium alloy, and a high-energy beam is irradiated to the attached part, and the hardening substance and titanium or titanium alloy are fused and integrated in the surface layer. A method for surface hardening treatment of titanium or titanium alloy, characterized in that: (2) The hardening substance according to claim 1, wherein the hardening substance is at least one selected from the group consisting of metal oxides, metal nitrides, metal carbides, hard intermetallic compounds, and hardenable alloy elements. Surface hardening treatment method.