JPS585256B2 - Sliding parts for internal combustion engines - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to members that require a high degree of wear resistance, such as piston rings or cylinder liners for internal combustion engines.

BACKGROUND ART In recent years, compression ratios and rotational speeds have been increased in order to improve the performance of internal combustion engines.

For this reason, there are inevitably great demands for wear resistance on piston rings or cylinders.

By the way, when classifying wear characteristics, the phenomena of abrasion (grinding wear caused by high-hardness foreign matter) and scuffing have a large impact on engine performance, so both abrasion resistance and scuffing resistance are considered to work together. For the first time, it exhibits excellent wear resistance.

Conventionally, as a wear-resistant measure, piston rings whose sliding surfaces are plated with chrome (hereinafter simply referred to as chrome-plated piston rings) or piston rings whose sliding surfaces are coated with molybdenum by thermal spraying (hereinafter simply referred to as molybdenum piston rings) are used. Thermal spray rings) are known.

However, chrome plating is expensive to process and has poor scuff resistance, so it is no longer able to meet the requirements.

On the other hand, molybdenum thermal sprayed rings have drawbacks in abrasion resistance, and molybdenum is expensive, so it is not common at present.

From this point of view, it is difficult to say that the above-mentioned chromium-plated piston rings and molybdenum sprayed rings have both abrasion resistance and scuff resistance at the same time, and their wear resistance is still insufficient.

Conventionally, as one of such wear-resistant measures, molybdenum and iron-based alloys are simultaneously sprayed on the contact surfaces of sliding members to form a mixture consisting of an iron-based alloy phase, an alloy phase of iron-based alloy and molybdenum, molybdenum, and voids. There is a known material in which a sprayed alloy layer is formed, and the known material is a mixture of molybdenum and an iron-based alloy in order to improve the bonding strength of the sprayed particles in the sprayed layer.

However, in the case of mixed spraying of molybdenum and iron, although the bonding strength of the sprayed particles in the sprayed layer has improved, the wear resistance is still insufficient.

The present invention provides a thermal sprayed layer that has further improved wear resistance in the above-mentioned known mixed thermal spraying of molybdenum and iron.

That is, in the sliding member for an internal combustion engine of the present invention, the wear-resistant thermal sprayed layer on the sliding surface, which is required to be wear-resistant, has a final composition of at least HV.
Metal carbide with a hardness of 750 or higher by weight ratio of 20
This is a sliding member for an internal combustion engine, characterized in that it consists of ~97% molybdenum, 0.5~4.5% molybdenum, and the balance iron or iron alloy.

If the hardness of the metal carbide used in the present invention is HV750 or less, excellent wear resistance as a sliding member for an internal combustion engine cannot be obtained, so a metal carbide having a hardness of HV750 or more is used.

A metal carbide having an HV of 750 or more contributes to wear resistance and increases the hardness of the entire sprayed layer, and if it is less than 20%, wear resistance and necessary hardness cannot be obtained.

If it exceeds 97%, the wear of the mating material that slides relative to it tends to be excessive, and scuffing tends to occur.

Molybdenum is partially alloyed with iron or iron-based alloys, and in terms of strengthening particle bonds, if it is less than 0.5%, the desired particle bonding by alloying with iron or iron-based alloys cannot be obtained. , the bonding strength of the particles is weak, and the peeling characteristics of the entire wear-resistant sprayed layer containing metal carbide and molybdenum cannot be improved.

If molybdenum exceeds 4.5%, the improvement in peeling properties, which is the effect of particle bonding due to alloying with iron or iron-based alloys, will not change much, and molybdenum has become expensive in recent years, resulting in high costs.4. It was limited to 5% or less.

Furthermore, the voids in the sprayed layer are extremely useful for retaining lubricating oil, but if the porosity exceeds 30%, the strength of the sprayed layer decreases, causing negative effects such as falling off of particles and peeling of the sprayed layer. Therefore, the porosity must be controlled to be 30% or less.

Furthermore, although the thermally sprayed layer of the present invention exhibits extremely excellent adhesion, it has been found that a thermally sprayed layer that is thermally sprayed to a thickness exceeding 2.5 mm is extremely susceptible to peeling. The critical thickness of the sprayed layer was determined to be 2.5 mm.

Therefore, it is necessary to use the sprayed layer at a thickness of 2.5 mm or less.

As described above, the present invention provides a thermal sprayed wear-resistant layer with an analytical value of at least H
Metal carbide with a hardness of v750 or more in a weight ratio of 2
A sliding member for internal combustion engines, characterized by consisting of 0 to 97% molybdenum, 0.5 to 4.5% molybdenum, and the balance iron or iron-based alloy, and has wear resistance that combines scuff resistance and abrasion resistance at the same time. A wear-resistant sliding member for an internal combustion engine on which a wear-resistant thermal sprayed layer is formed is obtained.

In order to prove the superiority of the sliding member of the present invention, a wear comparison test was conducted with a conventionally known member.

Sample 1 (15mm x 20mm x 7mm) Molybdenum powder 50% carbon steel powder (0.8%C)
50% was thermally sprayed to form a 0.5 mm thermal sprayed layer (porosity: 15%, hardness: HRC40).

Sample 2 (sample size same as sample 1) 16 chromium stainless steel powder 10% (16%Cr
, 2% Ni, 0.2% C, residual pig iron) Chromium carbide powder (13% C) 87% Molybdenum powder 3% was sprayed to 0
．． A sprayed layer of 5 mm (5% porosity was formed).

The composition of the sprayed layer is metal carbide (hardness Hv1,300)
83.7% molybdenum 3.
The balance was 1% iron-based alloy.

Sample 3 (sample size same as sample 1) Iron-iron carbide powder 97% (3.5%C
, residual pig iron) by spraying 3% molybdenum powder
．． A 5 mm sprayed layer (3% porosity) was formed.

The composition of the sprayed layer is metal carbide (hardness Hv950) 5
0% molybdenum 3% iron
It was the remainder.

Using a rotary abrasion tester, Samples 1 to 3 prepared in this manner were used as fixed pieces, and the fixed pieces were made of cast iron material (3.2% C, 2.0% Si, 0.0% 8%Mn,
Each test piece was pressed against the top surface of a disk-shaped sample (hardness: HRB98) made from iron residue), and the disk-shaped sample was rotated while constantly supplying lubricating oil to the press-contact surface, and the amount of wear after operation was measured. .

Test conditions Lubricating oil amount: 0.5 l/min Lubricating oil: Daphne oil #65 Load: 20 Kg/cm2 Friction speed: 5 m/sec Traveling distance: 300 km The above test results are as shown in Figure 1, and compared to conventional iron Sample 2.3 of the present invention showed a wear amount that was approximately 1/2 or less of Sample 1, confirming the superiority of the present invention, compared to Sample 1, which is a sprayed layer consisting of molybdenum and molybdenum.

In addition, the iron-based alloy in the present invention is carbon steel or 16
There are chromium-based stainless steels, etc., but depending on the type of iron-based alloy, the hardness of the entire sprayed layer may decrease, so care must be taken when selecting the iron-based alloy. It is necessary to select within the range that does not exceed

In addition, a method for obtaining a wear-resistant sprayed layer is to plasma-spray a mixture of individual powders of metal carbide, molybdenum, iron, or iron-based alloy to obtain a wear-resistant sprayed layer. One or a combination can be used.

Further, the thermal spray powder may be a mixture of two or three of iron-based carbide, molybdenum, and iron, and further, an alloy powder of iron-based carbide containing molybdenum may be used.

By plasma spraying these, a wear-resistant sprayed layer can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a graph showing the results of a wear comparison test between the sliding member of the present invention and a conventional member.

Claims (1)

[Scope of Claims] 1. A thermal sprayed wear-resistant layer formed by thermal spraying on the sliding surface of a sliding member for an internal combustion engine has a final composition of at least HV750.
Metal carbide having a hardness of 20 to 9 by weight
7% Mo, 0.5-4.5% Mo, and the balance iron or iron-based alloy. 2. The sliding member for an internal combustion engine according to claim 1, wherein the thermal sprayed wear-resistant layer has a porosity of 30% or less. 3. The sliding member for an internal combustion engine according to claim 1, wherein the thermal sprayed wear-resistant layer has a thickness of 2.5 mm or less.