JPH0286907A - Sliding member excellent in pitting fatigue abrasion resistance property - Google Patents

Abstract

PURPOSE:To improve the pitting fatigue abrasion resistance property even if the thickness of a membrane is less than a specified value by setting the hardness of a basic material beneath a membrane layer to a specified value, in a sliding member in which the membrane layer of metal nitride or metal carbide is formed on the surface of an iron based material. CONSTITUTION:A membrane layer consisting of metal nitride or metal carbide is formed on the surface of an iron based member, while the hardness of a basic member beneath the membrane layer is set to HmV400 or more, so that a sliding member excellent in pitting fatigue abrasion resistance property is formed. At this time, the iron based member is formed by using a carbon steel, a steel for carburization, a steel for nitrization and the like. On the other hand, the surface layer of metal nitride or metal carbide is formed by reactive ion plating, while using chrome nitride or the like for the class. In addition, the sliding member is used for example for the subject of a cam-follower, a bearing, gear and the like.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a sliding member with excellent pitting fatigue wear resistance, and more specifically, a sliding member with good durability when sliding under high surface pressure. Regarding sliding members.

(Prior technology and issues) In recent years, the number of cams used in camshafts has been reduced,
As engine speeds increase, there is a demand for engine designs that increase the force that presses the follower against the cam.As a result, the surface pressure between the cam and cam follower increases, causing wear in the high chromium chilled cast iron that has been widely used up until now. There have been many problems with durability. In response to this demand, sintered alloy followers are increasingly being used, but although sintered alloy followers do not wear out, they tend to attack the chilled mating cam nose, and when the surface pressure increases, It tends to cause scuffing with the cam nose. Further, there are disadvantages in that the cost of joining the sintered metal pad to the rocker arm and the high machining cost due to poor grindability. Therefore, in order to solve the above-mentioned problems, the present inventors developed a "transmission device" (Japanese Patent Application No. 132394/1983).
As an example, a cam follower treated with an ion-blating film such as a 1-100 μm Cr-N film has been filed. However, the Hertzian stress on the follower surface is 8
For requirements exceeding 0 kg/mm2, if the coating thickness is 1107z or less, pitting fatigue wear may occur if the fatigue strength of the base material at the depth where Hertzian stress is applied is poor.

(Object of the Invention) The present invention has been made in view of the above, and an object of the present invention is to provide a sliding member that has excellent pitting fatigue wear resistance even when the thickness of the metal nitride or metal carbide film is 10 μm or less. It is something.

(Means for Solving the Problems) The present invention provides a sliding member in which a metal nitride or metal carbide film layer is formed on the surface of an iron-based base material, wherein the base material hardness immediately below the film layer is HmV400 or more. This is a sliding member with excellent pitting fatigue and wear resistance.

Examples of the iron base material include carbon steel, carburizing steel, and nitriding steel.

The metal nitride or metal carbide surface layer is formed by reactive ion blasting.

A typical type of surface layer formed by reactive ion blasting is chromium nitride. Cr2N, CrN as chromium nitride
CrN has higher hardness than Cr and N and has excellent abrasion resistance, but the film tends to be less flexible and has relatively poor adhesion, but there is no problem in practical use (Patent Application No. 62 -3
No. 15751, No. 62316965). If it is necessary to further improve the adhesion under harsh conditions, first a layer of metallic chromium is formed on the surface of the material, then Cr2N-then C
By using a method of forming an rN film, it is possible to obtain a film with good adhesion and excellent wear resistance. Alternatively, an ultrafine mixed structure of metallic chromium, Cr2N, and CrN can be used (Japanese Patent Application Nos. 61-27772 and 59-2).
No. 07986).

The reason why the component constituting the surface layer is a layered structure of chromium and its nitride is that the chromium phase formed on the surface of the raw metal by reactive ion blasting has good adhesion to the raw metal, and This is because the coefficient of thermal expansion is close to that of the metal material, and therefore the surface layer can be prevented from peeling off from the metal material during use. Further, the reason why chromium is employed as a constituent of the surface layer is that the deposition rate of metallic chromium by ion blating is higher than that of other metals, and is extremely advantageous in terms of productivity.

In addition, we have developed a composite coating consisting of chromium nitride and titanium nitride (Japanese Patent Application No. 61-27773), a base layer consisting of metallic chromium and chromium nitride, and a composite coating consisting of a wear-resistant layer of titanium nitride on the base layer (Patent Application No. 61-27773). (Sho 61-124669), a surface layer made of a solid solution of titanium carbide and titanium nitride (Japanese Patent Application No. Sho 60-1)
No. 20563) etc. can be considered. Although titanium nitride has higher hardness and better wear resistance than chromium nitride, it is less flexible and peels more easily than chromium nitride, but titanium nitride alone poses no practical problem.

Examples of the sliding member include a cam follower, a bearing, and a gear.

The hardening treatment is performed before or after the ion-blating film treatment, and the thickness of the base material surface layer to be hardened is 0.1 mm or more of the base material directly below the film layer. Cured hardness is Hm V
If Hm V is 400 or more and less than 400, the object of the present invention cannot be achieved.

This will be explained in detail in the following examples.

(Example) Cylindrical shape (diameter 30 mm, thickness 8 mm) 5
The 45C and 80M420 materials were subjected to various hardening treatments, a CrN ion blating film was formed on the outer peripheral surface, and after puff finishing, they were subjected to the Nishihara pitting abrasion test.

The following three types of hardening treatment were used, and tempering treatment was added as a comparative example.

(Margin below, continued on next page) Table 1 heated to ℃.

The mating material for the test piece had a chilled surface with the following composition and had the same shape as the test piece.

Table 2: After forming a 10 μm CrN ion-blating film on the outer peripheral surface of the hardened test piece, the surface hardness of the base material directly under the film was measured and its distribution is shown in FIG. Incidentally, a test was conducted using a test device having a main mechanism as shown in FIGS. 1(a) and 1(b) using test pieces prepared in a manner similar to about 400 or more during ion blating.

Among the upper and lower test pieces, the upper test piece was the test piece of the present invention and the comparative example, and the lower test piece was the counterpart test piece. The rotation speed of the upper test piece was set to 166.5 ppm, and the rotation speed of the lower test piece was set to 185 rpm to produce 10% slippage. The sliding speed was 0.39 m/sec, and the contact load (Hertzian maximum stress) was 80 to 220 kg/mm2. Mechanically, tensile stress is applied to the upper test piece and compressive stress is applied to the lower test piece, so pitting wear occurs on the upper test piece.

Here, the Hertzian maximum stress PH is expressed by the following simplified formula.

(Effects) The present invention provides a sliding member with excellent pitting wear resistance even when the ion blating film thickness is 10 μm or less by setting the base material hardness immediately below the ion brating film to Hm V 400 or more. be able to.

Here, W is the load, L is the thickness of the test piece, R is the diameter of the test piece, R1 is the diameter of the upper test piece, R2 is the diameter of the lower test piece, E is Young's modulus, and El is Young's of the upper test piece. The modulus, R2, is the Young's modulus of the lower specimen.

The above four types of test pieces were tested and the results shown in Figure 2 were obtained.

As is clear from the test results, the Hm V 40 of the present invention
It was confirmed that the ion brazing film having a base material hardness of more than 0 has excellent pitting fatigue wear resistance.

[Brief explanation of drawings]

Figure 1 shows the main mechanism of the Nishihara pitching wear test device; a) is a schematic front view thereof, (b) is a schematic side view thereof, Figure 2 is a graph showing the hardness distribution of the test piece, and Figure 3 is a diagram showing the distribution of hardness of the test piece. The figure is a graph showing the SN curve of the Nishihara pitching wear test. In the figure: l...upper test piece, 2...lower test piece, W.
...Load, L...Thickness of test piece, R□...Diameter of upper test piece, R2...Diameter of lower test piece, Young's modulus of upper test piece, R2...Diameter of lower test piece Young's modulus.

Claims (1)

[Claims] 1. A sliding member having a metal nitride or metal carbide film layer formed on the surface of an iron-based base material, characterized in that the base material hardness immediately below the film layer is HmV400 or more. Sliding member with excellent properties.