HEAT-RESISTANT BEARING MATERIAL

Abstract

A heat-resistant bearing material consisting of an austenitic iron matrix alloy should, under high temperatures, have good solid lubricant properties with a high heat resistance and a high creep resistance. To this end, an iron matrix alloy is used, containing a sufficient sulphur part for obtaining a solid lubricant action on the bearing surfaces thereof, and between 1 and 6 wt. % of at least one of the following alloy elements: tungsten (W), cobalt (Co), niobium (Nb), rhenium (Re), molybdenum (Mo), tantalium (Ta), vanadium (V), hafnium (Hf), yttrium (Y), zirconium (Zr), and/or comparably high-melting alloy elements.

Description

The invention relates to a heat-resistant bearing material consisting of an austenitic iron matrix alloy, and here addresses the problem of making such a bearing material functionally reliable for use at high temperatures, especially at temperatures exceeding 600° C., in particular exceeding 850° C. The bearing material here is to exhibit solid lubricant properties, which are to be retained at the specified high temperatures to as high a degree as possible.

This object is achieved by means of a bearing material according to the characterizing features of claim 1

Advantageous alloys of such a bearing material are the subject matter of the subclaims.

The invention is based on the general idea of providing sulfur in a percentage amount that allows sulfides required for a lubricating effect to form within the alloy. Such a formation of sulfide within an austenitic matrix alloy intended to exhibit a high creep resistance and high strength at high temperatures is a contradiction in and of itself. This contradiction stems from the fact that, based on general expert knowledge, sulfides contained in such a material are disadvantageous for a high creep resistance and high strength at high temperatures because they constitute a structural disturbance, and must therefore be avoided. Therefore, the invention proposes something that runs absolutely counter to general expert knowledge with respect to the objective of obtaining a material that is highly creep resistant and strong in terms of temperature, and still exhibits lubricating properties even at high temperatures, and hence represents a surprising result not to be expected by an expert.

The drawing shows a few diagrams depicting characteristics for bearing materials according to the invention. The curves denoted in individual diagrams relate to a material according to claim 7 if marked A, and a material according to claim 8 if marked B.

EXPLANATION TO INDIVIDUAL DIAGRAMS

FIG. 1 a, 1b

These diagrams show the creep behavior of alloys A and B during the gradual exposure of a sample in increments of 2 MPa, a retention period of 35 sec and when measuring the creep rate in the last 5 sec of the retention period, specifically in part a for a creep behavior at 700° C., and in part b for a creep behavior at 900° C.

FIG. 2

This diagram records the modulus of elasticity E and sheer modulus G for alloys A and B as a function of temperature.

FIG. 3

This diagram depicts the thermal expansion coefficient for alloys A and B as a function of temperature.

FIG. 4

This diagram records the hot hardness (in HV10) on the ordinate as a function of the temperature for alloys A and B.

FIG. 5

The ordinate shows the hardness (in HB 2.5/187.5) for alloys A and B after stored for a respective 2 hours and air-cooled as a function of temperature.

FIG. 6

This figure contains a table that indicates values for p =density, λ=heat conductivity, R_p02=expansion limit, R_m=tensile strength, E=modulus of elasticity for alloys A and B at respective room temperature.

All features described in the specification and the following claims can be significant to the invention both individually and taken together in whatever form.

Claims

1. A heat-resistant bearing material that is an austenitic iron matrix alloy, consisting of: a sufficient sulfur percentage to achieve a solid lubricant action on bearing surfaces of the bearing material, andbetween 1% w/w and 6% w/w of at least one or more of the melting alloy elements:tungsten (W), cobalt (Co), niobium (Nb), rhenium (Re), molybdenum (Mo), tantalum (Ta), vanadium (V), hafnium (Hf), yttrium (Y), zirconium (Zr) and an alloy with a comparable melting point to the melting alloy elements; andwherein the following alloy composition is included, where the individual alloy elements are each indicated in % w/w:

2. The bearing material according to claim 1, wherein the following alloy composition is included, where the individual alloy elements are each indicated in % w/w:

3. The bearing material according to claim 1, wherein the following alloy composition is included, where the individual alloy elements are each indicated in % w/w:

4. The bearing material of claim 1, wherein a paddle bearing ring is constructed of the bearing material.