JPH02243776A - Composite surface hardening method - Google Patents

Abstract

PURPOSE:To harden the surface of a composite material and to improve its wear resistance by removing only a matrix on the composite material surface to a specified thickness and pressing the exposed ceramic grains or short fibers into the matrix by plastic working. CONSTITUTION:Only the matrix on the composite material surface consisting of the ceramic grains or short fibers and a matrix metal is removed to a specified thickness. The thickness to be removed is appropriately controlled to the thickness of about 2 times the fiber diameter or 1/2-2/3 times the average grain diameter. In this case, the matrix is dissolved in hydrochloric acid, etc., and removed. Consequently, a part of the ceramic grains or short fibers is exposed. The exposed ceramic grains or short fibers are pressed into the matrix by plastic working. The plastic working is carried out preferably at a temp. below that of the solidus line of the matrix. The exposure-pressing process is performed once or repeated several times, as required. By this method, the content of the fiber, grain, etc., of the composite material surface is enhanced, surface density is increased and the wear resistance is improved by the plastic working.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for surface hardening a composite material comprising a reinforcing material such as fiber reinforcement or particle reinforcement and a metal matrix.

[Conventional technology and its issues]

The mainstream manufacturing methods for composite materials that can be processed primarily include molten metal forging, in which a fiber preform is impregnated with matrix molten metal, and powder metallurgy methods, such as mixing fiber particles and matrix powder, compacting, sintering, and extrusion. .

In the molten metal forging method in which the above preform is impregnated with matrix molten metal, the fiber content (Vf
), and the upper limit is around 30%.

Powder metallurgy, on the other hand, does not have this restriction. However, short fibers
From the point of view of secondary processability, which is a characteristic of composite materials using particles, Vf is set at about 35% at most.

Because of these limitations in the content of fibers, particles, etc., composite materials have many excellent properties, but have a problem in terms of wear resistance, which is not as good as ceramics or special steels.

[Problems to be Solved by the Invention] The present invention was made as a result of studies on the above-mentioned problems, and is a composite material that is lightweight, has excellent abrasion resistance, hot strength, etc., and has particularly improved abrasion resistance. This is a surface hardening method developed.

[Means and effects for solving the problem] The present invention removes only a predetermined thickness of the matrix on the surface of a composite material consisting of ceramic particles or short fibers and matrix metal, and exposes a part of the ceramic particles or short fibers. This is a surface hardening method for a composite material, which is characterized in that the step of press-fitting ceramic particles or short fibers exposed by plastic working into a matrix is repeated once or multiple times.

That is, the present invention removes only a predetermined amount of the matrix on the surface of the composite material in a process that approximates the desired shape of the composite material,
By press-fitting the exposed particles and fibers into the matrix through plastic processing, the content of fibers and particles in the composite material is substantially increased, increasing the density of fibers and particles at least on the surface, thereby increasing hardness and improving wear resistance. It is something that forces you to do something.

However, it is necessary to select the thickness of the matrix removed so that the particles and fibers exposed by removing the matrix function effectively in the next press-fitting process by plastic working, and this thickness In the case of , about twice the fiber diameter,
In the case of particles, it is appropriate to remove about 1/2 to 2/3 of the particle average diameter in the matrix.

In the case of fibers, this is based on an aspect ratio that will not cause fiber breakage, and in the case of particles, it is expected that large particles that contribute to press-fitting will remain effectively.

Also, although it is effective to just press fit, it is desirable to cut and remove the exposed portion at the interface between the press fit particles/fibers and the matrix, as there are defects such as the presence of oil and fat.

This process of removing and press-fitting the matrix only once is effective, but by repeating it multiple times, the content of particles and fibers in the matrix can be further increased. Further, the plastic working described above can be performed satisfactorily by performing the plastic working at a temperature below the solidus line of the matrix.

In this way, the present invention increases the content of particles and fibers in the composite material by removing only the surface matrix and press-fitting the exposed ceramic particles and short fibers in the composite material manufacturing process. , which improves wear resistance.

Therefore, the present invention can be applied during the normal manufacturing process of this type of composite material, and the range of application is extremely wide, and its effects are remarkable.

〔Example〕

An embodiment of the present invention will be described below.

SiC particles with an average particle size of 100μ and Le gold alloy 6061 powder were mixed in SiC V (20%), mixed in a ball mill for 8 hours, then compacted, housed in a pure A2 can, and heated at 450°.
Vacuum degas while heating to C, 1,2 x 10-2T
It was sealed at a vacuum level of orr. It was then extruded into round bars at 470°C and an extrusion ratio of 10. Further, this was drawn into a wire of 10 mmφ. The surface hardness of this cotton is Hv
=90. Next, the aluminum alloy on the surface was dissolved and removed using hydrochloric acid. At this time, melting conditions were set in advance so that the difference in level between the SiC particles and the melted aluminum alloy was approximately 50 μm.

Thereafter, it was drawn to a diameter of 9.95 mm and the surface hardness was measured, and the result was Hv=110. From this state, do the same as above to get A of the matrix! Dissolve and remove 9 with 50μ of hydrochloric acid.
．． It was set to 90+nmφ. In this case, hardness stripe 1 (v=1
It was 30. After cutting this drawn material to 9.85 mmφ with a centerless grinder, the hardness was measured.
v=125. Further, as a result of measuring the Vf of SiC from the surface structure photograph, a high value of approximately 40% was obtained.

From these results, it is clear that the present invention significantly increases surface hardness and improves wear resistance, and furthermore, it was recognized that the particle content was significantly increased.

〔effect〕

As explained above, the present invention can enrich the required wear-resistant surface with the amount of particles and m-fibers that cannot be achieved with conventional methods, resulting in high hardness and excellent wear resistance. It is a composite material that can be obtained and has remarkable industrial effects.

Claims (2)

[Claims] (1) Only the matrix on the surface of a composite material consisting of ceramic particles or short fibers and matrix metal is removed to a predetermined thickness to expose a part of the ceramic particles or short fibers, and then the exposed ceramic particles or short fibers are processed by plastic processing. A method for surface curing a composite material, comprising repeating the step of press-fitting fibers into a matrix once or multiple times. (2) The method for surface treatment of a composite material according to claim 1, characterized in that the plastic working is performed at a temperature below the solidus line of the matrix.