JPH0587673B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method of manufacturing sliding members for internal combustion engines, such as piston rings, cylinder liners, tappets, rocker arms, etc.

[Conventional technology]

Sliding members used in reciprocating internal combustion engines are required to have a high degree of wear resistance. Therefore, for the purpose of imparting wear resistance to sliding members for internal combustion engines, forming a hard chromium plating film on the sliding surfaces has been frequently used. ” [Problems to be solved by the invention] However, in recent years, internal combustion engines have become faster and more powerful, and the conditions for their use have become increasingly severe. Sliding members for internal combustion engines having plating films do not have sufficient wear resistance or corrosion resistance.

The present invention has been made in view of the above,
It is an object of the present invention to solve the above problems and provide a method for manufacturing a sliding member for an internal combustion engine that has excellent wear resistance and corrosion resistance.

[Means for Solving the Problems] The structure of the present invention for achieving the above object is to coat at least one sliding surface with an amorphous hard chromium film of 5 μm to 200 μm by plating. This is a method of manufacturing a sliding member for an internal combustion engine.

[Example] Examples of the present invention will be described below based on the drawings.

FIG. 1 shows a piston ring 1, which is an example of a sliding member for an internal combustion engine, in which an amorphous hard chromium plating film 3 is formed on the outer peripheral surface of a piston ring base material 2. The piston ring base material 2 is made of ordinary stainless steel or cast iron.

The amorphous hard chromium plating film of the sliding member of the present invention has a plating solution containing 50 to 50% chromic acid.
200g/, sulfuric acid 2-10g/formic acid (concentration 85%)
It is formed by plating at a bath temperature of 20 to 60°C and a current density of 20 to 60 A/dm ² using a mixture containing 2 to 50 ml of . Since the formic acid (HCOOH) functions as a brightening agent in conventional plating, the crystals become dense and amorphous. Therefore, if it is a brightening agent for chrome plating,
Acetic acid (CH ₃ COOH), formaldehyde (HCHO) or acetaldehyde (CH ₃ CHO) may also be used.

One side of a flat steel plate measuring 18mm x 12mm x 6mm was lapped to give a surface roughness of 11μ or less and used as a sample material. The surfaces of this sample other than those with surface roughness of 1 μ or less were sealed, and the plating solution was chromic acid: 100 g/,
_H2SO4 : _5g /, Formic acid (HCOOH): 20ml/
Plating was performed in a bath at a bath temperature of 30° C. and a current density of 40 A/dm ² to form an amorphous hard chromium plating film. At this time, the film thickness was 50μ and the hardness was Hv1030. (Sample No. 1...Invention) The sample No. 1 was heat-treated at a temperature of 200° C. for 1 hour. The thickness of the film at this time was 50μ, and the hardness was
It was Hv1100. (Sample No. 2...Invention) The sample No. 1 was heat-treated at a temperature of 300° C. for 1 hour. The thickness of the film at this time was 50μ, and the hardness was
It was Hv1200. (Sample No. 3...Invention) As for conventional hard chromium plating, the most commonly used chromium plating bath is the so-called sergeant bath, in which the plating solution is chromic acid: 250g/ , H ₂ SO ₄ : 2.5 g/bath temperature: 60
Plating was performed at °C and current density: 60A/ ^dm2 . The thickness of the film at this time was 50μ, and the hardness was Hv880. (Sample No. 4: Conventional Example) The structure of the plated film was determined by X-ray analysis. As is clear from Figures 4a to 4d,
Samples Nos. 1 to 3 are amorphous, while sample 4 shows crystalline chromium.

A wear resistance test and a corrosion resistance test were conducted on the above samples Nos. 1 to 4.

(Abrasion resistance test) The above samples No. 1 to 4 are used as fixed pieces, and the mating members are:
Disc-shaped test piece (outer diameter 139 mm, inner diameter 105 mm, thickness 7
mm, material: FC25, hardness: HRB98), set it so that the glazing film formed on the fixed piece was in contact with the disk-shaped test piece, and rotated the disk-shaped test piece while supplying lubricating oil. After sliding, the wear charge of the fixed piece was measured.

The test conditions are as follows.

Sliding speed: 1.1m/sec Sliding distance: 30.7Km Lubricating oil: SAE#30 motor oil Lubricating oil supply conditions: 100ml/min, oil temperature 60℃~65
℃ Contact load of test piece: 80Kg The test results are shown in Figure 2.

As is clear from the figure, samples No. 1 to 3 of the present invention are
It exhibited better wear resistance than the conventional sample No. 4.

Note that when the conventional hard chrome plating film was heat treated under the above conditions, the hardness decreased, so it was not used in the test. This is thought to be due to the release of occluded hydrogen in the film.

(Corrosion resistance test) Regarding sample Nos. 1 to 4, the surface of each sample other than the plated film was sealed with a tetrafluoroethylene resin tape, and the sample was immersed in a solution of hydrochloric acid (HCl) and sulfuric acid (H ₂ SO ₄ ). After each immersion, the seal was peeled off and the loss due to corrosion was measured.

The test conditions are as follows.

Hydrochloric acid, sulfuric acid concentration: 2.5% Liquid temperature of hydrochloric acid and sulfuric acid: 70℃ Volume of hydrochloric acid and sulfuric acid: 1000ml Soaking time: 25 minutes The test results are shown in Figure 3.

As is clear from the figure, samples No. 1 to 3 of the present invention
showed better corrosion resistance than the conventional sample No. 4. This is thought to be due to the progression of intergranular corrosion of chromium crystals in the conventional hard chromium plating film.
In addition, the white bar graph in the figure is hydrochloric acid (HCl).
The diagonal bar graph shows the test results when sulfuric acid (H ₂ SO ₄ ) was used.

In the internal combustion engine sliding member of the present invention, the hardness of the amorphous hard chromium plating film is as follows:
Hv1030 to Hv1200, which cannot be obtained with conventional hard chrome plating films. Regarding the thickness of the coating, there are various types for sliding members of internal combustion engines, but a coating thickness of about 5 μm to 200 μm is sufficient.

[Effects of the Invention] As described above, the sliding member for an internal combustion engine obtained by the manufacturing method of the present invention has an amorphous hard chromium plating film on its sliding surface. Therefore, it has not been possible to obtain a conventional hard chromium plating film having crystalline chromium. It provides wear resistance and corrosion resistance, and its effects are particularly remarkable as sliding members of internal combustion engines used under severe operating conditions.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a piston ring which is an example of a sliding member for an internal combustion engine according to the present invention, FIG. 2 is a graph showing the results of a wear resistance test, and FIG. 3 is a graph showing the results of a corrosion resistance test. Figure 4 shows the X for each sample.
FIG. 3 is a diagram showing a line analysis chart. Symbols in the figure: 1... Piston ring, 2... Piston ring base material, 3... Amorphous hard chromium plating film.

Claims (1)

[Claims] 1. A method for manufacturing a sliding member for an internal combustion engine, characterized in that at least one sliding surface is coated with an amorphous hard chromium film of 5 μm to 200 μm by plating.