JPH07138755A - Surface reforming method for iron and steel material - Google Patents

Abstract

PURPOSE:To enhance the durability of implanted layers in the method for improving the wear resistance of the surfaces of iron and steel products by a titanium ion implantation by implanting the titanium ions to the surfaces after previously increasing the carbon concn. of the surface layers by subjecting the surface layers to a carburization treatment prior to titanium ion implantation. CONSTITUTION:The carbon concn. of the surface layers are increased by subjecting the material to be treated to the carburization treatment. The surface layers having the excellent wear resistance is formed by implanting the titanium ions into such layers even if additional implantation of carbon ions is not executed. The amt. of the titanium ions to be implanted is preferably >=1X10<17>atoms/ cm<2> and <=2X10<18>atoms/cm<2>.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for modifying the surface of a steel material having a surface having excellent wear resistance.

[0002]

2. Description of the Related Art It is well known that implanting titanium ions into a steel material improves the wear resistance of the surface (for example, IL Singer, Appl. Surface Sci., 1
8 (1984) p28-p62). This is because a carbon-containing gas in a vacuum is adsorbed during the injection of titanium into the steel material, and carbon in the gas is taken into the injection surface of the steel material to form an amorphous phase of the iron-titanium-carbon system. It depends. This amorphous phase, when the steel material is placed in a friction wear environment,
Although the wear resistance is improved by reducing the friction coefficient of the steel material, the durability of the amorphous phase itself is not sufficient. To improve the durability of the amorphous phase of iron-titanium-carbon system, by intentionally introducing carbon into the implantation layer by additionally implanting carbon ions after titanium ion implantation, and improving the surface characteristics. Have been done (eg DM Folls
taedt, JA Knapp and LE Pope, MRS Res. Soc. Sym
p. Proc. vol140 p133-p146), but this method has the drawback of increasing the processing time and increasing the cost.

[0003]

SUMMARY OF THE INVENTION It is an object of the present invention to improve the wear resistance of a steel material by ordinary titanium ion implantation without significantly increasing the processing time and cost of the additional carbon ion implantation. An object of the present invention is to provide a method for modifying the surface of a steel material that can improve the wear resistance of the surface.

[0004]

According to the present invention, the above object is to carry out a carburizing treatment on a steel material, and to implant titanium ions into the steel material subjected to the carburizing treatment. This is accomplished by providing a surface modification method.

[0005]

OPERATION Originally, the composition of the steel material is adjusted so as to satisfy the required material properties, so the carbon content of the material cannot be freely changed. On the other hand, as a method of increasing only the amount of carbon in the surface layer of a steel material, there is a carburizing method in which carbon is diffused and permeated from the surface and the toughness can be maintained while maintaining low carbon in the central part. Therefore, if a normal carburizing process is performed, the amount of carbon only in the surface layer can be increased and the components inside the material can be left as they are. When a normal titanium ion implantation is performed on steel material that has been subjected to carburizing treatment to increase the carbon concentration of the surface layer, this is a surface containing a large amount of carbon, so even if additional implantation of carbon ions is not performed after the titanium ion implantation. It is possible to form a sufficiently durable surface layer.

[0006]

EXAMPLES Preferred examples using the AISI 4130 steel according to the present invention will be described below. H ₂ O produced by decomposing a mixed gas of methane gas and air using a Ni catalyst
In an end gas having a composition of about 20% CO, about 40% H _{2, and} about 40% N ₂ , the AISI 4130 steel is 900
It was heated to 0 ° C. and directly quenched to form a carburized layer having a depth of 0.1 mm on the surface layer. AISI413 not carburized
No. 0 steel and carburized AISI 4130 steel with titanium ion acceleration energy of 140 kV and injection amount of 5 × 10 ¹⁷
It was injected under the condition of atoms / cm ² . Friction and wear characteristics of four types of AISI4130 steels, which were untreated, carburized only, titanium ion-implanted only, and carburized titanium-ion-implanted, were examined by a linear reciprocating wear test. The test conditions were load: 1000 gf, sliding speed: 10 mm / sec, number of sliding times: 500, and mating pin: SUS440C. Table 1 shows the friction coefficient at the end of the test and the depth of wear marks measured by a precision roughness meter.

[0007]

[Table 1]

As is clear from this table, the amount of wear of the sample into which titanium ions were injected after the carburizing treatment was remarkably small. The implantation amount of titanium ions after the carburizing treatment is 1 × 10 ¹⁷
atoms / cm ² or more and 2 × 10 ¹⁸ at
It is desirable that it is oms / cm ² or less. This is because, since the titanium concentration on the surface is saturated by sputtering, there is not much effect even if the injection amount is increased by 2 × 10 ¹⁸ atoms / cm ² or more, and the titanium concentration on the surface is less than 1 × 10 ¹⁷ atoms / cm ^2. The reason for this is that the desired characteristics cannot be sufficiently obtained because of low amorphism and no amorphization. The energy of titanium ions is preferably 50 kV or more and 400 kV or less. This is because when the ion implantation depth of titanium ions is 50 kV or less, the titanium concentration on the surface is saturated due to sputtering and a sufficient titanium concentration cannot be obtained, and when 400 kV or more, the implantation apparatus is large. It is not practical as an industrial process.

[0009]

As is apparent from the above description, according to the present invention, carbon ions are added after titanium ion implantation by performing ordinary titanium ion implantation after performing an ordinary carburizing treatment, which is an inexpensive treatment. Without injecting
A steel material having sufficient wear resistance can be manufactured.

Claims (1)

[Claims] 1. A method for modifying a surface of a steel material, which comprises carburizing the steel material and implanting titanium ions into the carburized steel material.