JPS589830B2 - Sintered alloy for corrosion-resistant sliding parts - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a sliding member manufactured by powder metallurgy and having excellent abrasion resistance and sliding properties at high temperatures.

In recent years, with the remarkable development of industry, the lubrication elements tend to be hotter due to improvements in efficiency and higher speeds, especially in space equipment, nuclear power industries, etc., and the demand for materials with excellent high-temperature sliding properties, such as high-temperature bearings, has increased. ing.

Currently, tools commonly used as high-temperature sliding materials such as high-temperature bearings include tool steel, high-melting point metals, superalloys, cermets, ceramics, and graphite. Although they have excellent heat resistance and abrasion resistance, they have extremely poor workability and are made of high-grade materials.
Although ceramic is relatively inexpensive, it has the disadvantage of being weak against impact, and graphite has strength problems and deteriorates wear resistance in an oxidizing atmosphere at temperatures above 500°C. There is a problem.

The present invention aims to improve these drawbacks and provide a high-temperature corrosion-resistant sintered alloy for sliding members that has excellent heat resistance, oxidation resistance, abrasion resistance, and strength characteristics, and is relatively inexpensive. be.

Such materials are manufactured, for example, by the following method.

(All percentages below indicate weight percentages.) 5-11% N
i powder and 4-9% Cr powder (or Fe- as Cr)
Cr powder), 3-8% Co powder, Mo and Fe-M
5 to 20 with o powder as Mo and Pb, Sb, Bi, S
At least one of the low melting point metals n, Ag in total 1
~15%, mixed with the remaining iron powder to make 100%, first cold-formed to a density of 80-90%, and then heated at 1200'C.
Sintering is performed in the above reducing atmosphere (H2 or vacuum) for about 1 hour.

The obtained sintered body has a density of 80 to 85%, but in this state, the metal matrix is in a state of solution softening, and the hardness is less than mHv 300, making it extremely easy to process, including cutting. It is.

In this state, the hardness is low, so the wear resistance cannot be said to be sufficient, but by aging at 500 to 650°C for about 1 hour, the matrix has a Vickers hardness of 5.
It hardens from 00 to 600, improving wear resistance.

In addition, when blending the powder, MO or Cr may be blended in the form of a hard iron compound and left as a hard dispersed phase by sintering to further improve the wear resistance.

Among the constituent components, Ni plays a role in improving corrosion resistance and heat resistance, but if it is less than 5%, the effect is small, and if it is more than 11%, corrosion resistance increases, but austenite becomes stable and precipitation hardenability decreases. It was set at 5 to 11%.

Cr is also an element that improves corrosion resistance, heat resistance, and oxidation resistance, and if it is less than 4%, the effect is small, and if it is more than 9%, it becomes difficult to obtain a state of solution softening during sintering, making processing difficult. 4 to 9%.

Co has the effect of improving the heat resistance of the matrix and promoting the precipitation of FeMo2 from the matrix. If it is less than 3%, the effect is small, and even if it is more than 8%, the effect remains unchanged. It shall be 8%.

Mo also contributes to the improvement of heat resistance and oxidation resistance, and is precipitated from the matrix in the form of Fe2Mo by aging treatment and plays a major role in hardening, but if it is less than 5%, hardening is insufficient.

In some cases, a portion of Mo may be left as a hard Fe-Mo compound, but even in this case, it is necessary to dissolve at least 5% Mo in the matrix.

However, even if the amount of Mo exceeds 20%, the amount of hardening will not change and only the brittleness of the material will increase. It is present in a metal matrix of 1 to 15%, and becomes molten in a high-temperature atmosphere or due to a temperature rise during sliding, and leaches into the sliding surface through pores, playing the role of lubrication.

If the content is less than 1%, this lubricating function will be insufficient, and if the content is more than 15%, the overall strength will be reduced, so it is set at 1 to 15%.

As mentioned above, the characteristics of the material of the present invention are that it consists of a metal matrix that is age hardenable, corrosion resistant, and wear resistant, and a low melting point metal component that becomes molten at high temperatures and exhibits excellent lubricity. It exhibits excellent wear and sliding properties even in high-temperature oxidizing atmospheres where oil lubrication cannot be expected.

This will be described in more detail in Examples below.

Example-325 mesh carbonyl nickel powder, Fe-Cr
powder, metallic cobalt powder, and Fe-Mo powder and -25
0 mesh Pb, Sb, Sn, Bi, and Ag were blended into the following composition, and after mixing, molded to a density of 85%, and then 126
Sintering was performed at 0°C for 1 hour.

The obtained sintered material was subjected to an abrasion test at 350°C.

(Numbers in the composition below indicate %) A Fe- 8Ni-6Cr-7Co- 8Mo- 5
PbB Fe- 8Ni-6Cr-7Co- 8Mo-
5Pb-3SbC Fe- 8Ni-6Cr-7Co
- 8Mo- 5Pb-3SnD Fe- 8Ni-6
Cr-7Co- 8Mo- 5Pb-IAgE Fe-
10Ni-9Cr-3Co-10Mo-5Pb-3B
iF Fe-5Ni-9Cr-8Co-10Mo-1
0PbG Fe- 8Ni-3Cr-7Co- 8Mo
-10PbH Fe- 8Ni-6Cr-7Co-15
Mo- 5Pb-3Sn- 2Bi 2 High temperature wear test (test conditions) (1) Temperature 350°C (in air) (2) Contact pressure 2kg/cm2 (3) Friction speed 1.5m/sec (4) Friction distance 300m (5) Compatible material SUH3B (hardness HRC40) (comparison material) 21-4N steel Hardness HRC40 Stellite No. 6 Hardness HRC48 As can be seen from the above examples, the material of the present invention has wear resistance comparable to Stellite steel in a temperature atmosphere of 3000 G or more, and is suitable for sliding members used in high temperature and oxidizing atmospheres, such as Ideal for high temperature bearings and various sealing materials.

In the production of this material, in addition to the production method described in the examples, if a powder with a matrix composition is prepared in advance by the atomization method, the structure of 71 to 1000x will be homogenized, and the age hardenability and Heat resistance and oxidation resistance are improved.

In addition to the method of incorporating a lubricating component in the form of powder before sintering, the same effect can be obtained by impregnating it after sintering and heat treatment.

Claims (1)

[Claims] 1% by weight: Ni5-11%, Cr4-9%, Co3-
Pb, Sb, Bi,
A sintered alloy for a sliding member having excellent corrosion resistance and excellent sliding properties at high temperatures, containing at least one of low melting point metals such as Sn and Ag in a total weight percent of 1 to 15%.