Heat-resistant bearing material made of an austenitic iron matrix alloy

Abstract

A heat-resistant bearing material may include an austenitic iron matrix alloy having a proportion of sulphur sufficient to achieve a solid lubricating action on bearing surfaces of the heat-resistant bearing material. The iron matrix alloy may have a proportion of carbides to achieve a reduction of wear on bearing surfaces of the heat-resistant bearing material and a proportion of 1 to 6 percentage by weight of at least one alloying element including cobalt, niobium, rhenium, tantalum, vanadium, tungsten, hafnium, yttrium and zirconium. The iron matrix alloy may also include the following alloying elements: carbon, chromium, manganese, silicon, nickel, molybdenum, niobium, tungsten, sulphur, copper, nitrogen and iron.

Claims

1. A bearing material, comprising: an austenitic iron matrix alloy having a proportion of sulphide-based solid lubricant particles to provide a solid lubricating action on bearing surfaces of the bearing material, a proportion of carbides to provide a reduction of wear on bearing surfaces of the bearing material, and a proportion of 1 to 6 percentage by weight of at least one alloying element including cobalt (Co), rhenium (Re), tantalum (Ta), vanadium (V), hafnium (Hf), yttrium (Y), and zirconium (Zr), wherein the iron matrix alloy in addition to the proportion of 1 to 6 percentage of the at least one alloying element further includes a composition of the following alloying elements, with respective percentages by weight: carbon (C)=0.8 to 2.0; chromium (Cr)=20-32; manganese (Mn)=0-1.0; silicon (Si)=1.5-3.5; nickel (Ni)=12-25; molybdenum (Mo)=0.5 to 5.5; niobium (Nb)=1-3.5; tungsten (W)=1.0-6.5, sulphur (S)=0.15-0.5; copper (Cu)=0-3.5; nitrogen (N)=0-0.8, and iron (Fe), the remainder including unavoidable impurities.

2. The bearing material according to claim 1, wherein the composition of alloying elements has the following respective percentages by weight: carbon (C)=0.9 to 1.4; chromium (Cr)=21-28; manganese (Mn)=0.1-1.0; silicon (Si)=2.0-3.5; nickel (Ni)=14-23; molybdenum (Mo)=1.5 to 3.5; niobium (Nb)=1.0-3.0; tungsten (W)=2.0-3.5; sulphur (S)=0.15-0.5; copper (Cu)=1.0-3.5; nitrogen (N)=0.1-0.8, and iron (Fe), the remainder including unavoidable impurities.

3. The bearing material according to claim 2, wherein the proportion of sulphur is at least 0.2 percentage by weight.

4. The bearing material according to claim 1, wherein the bearing material is disposed in at least one of a turbocharger and an exhaust gas recirculation system for regulating flow in an internal combustion engine.

5. The bearing material according to claim 1, wherein at least one of the proportion of sulphur is at least 0.2 percentage by weight and the proportion of manganese ranges from 0.1 to 1.0 percentage by weight.

6. The bearing material according to claim 1, wherein the proportion of carbon ranges from 0.9 to 1.4 percentage by weight.

7. The bearing material according to claim 1, wherein some of said carbon is precipitated as fine carbon particles in the austenitic iron matrix alloy.

8. A bearing element for at least one of a turbocharger and an exhaust gas recirculation system for regulating flow in an internal combustion engine, comprising: a bearing material having an austenitic iron matrix alloy, the iron matrix alloy including: a proportion of sulphide-based solid lubricant particles to provide a solid lubricating action on bearing surfaces of the bearing material; a proportion of carbides to provide a reduction of wear on bearing surfaces of the bearing material; a proportion of 1 to 6 percentage by weight of at least one alloying element including cobalt (Co), rhenium (Re), tantalum (Ta), vanadium (V), hafnium (Hf), yttrium (Y), and zirconium (Zr); and wherein the iron matrix alloy in addition to the proportion of 1 to 6 percentage by weight of the at least one alloying element has the following composition of alloy elements by weight: carbon=0.8 to 2.0; chromium=20 to 32; manganese=0 to 1.0; silicon=1.5 to 3.5; nickel=12 to 25; molybdenum=0.5 to 5.5; niobium=1 to 3.5; tungsten=1.0 to 6.5; sulphur=0.15 to 0.5; copper=0 to 3.5; nitrogen=0 to 0.8; and iron with a remainder including unavoidable impurities.

9. The bearing element according to claim 8, wherein the composition of the alloying elements has the following percentages by weight: carbon=0.9 to 1.4 chromium=21 to 28; manganese=0.1 to 1.0; silicon=2.0 to 3.5; nickel=14 to 23; molybdenum=1.5 to 3.5; niobium=1.0 to 3.0; tungsten=2.0 to 3.5; sulphur=0.15 to 0.5; copper=1.0 to 3.5; nitrogen=0.1 to 0.8; and iron with a remainder including unavoidable impurities.

10. The bearing element according to claim 9, wherein the proportion of sulphur is at least 0.2 percentage by weight.

11. The bearing element according to claim 8, wherein the proportion of sulphur is at least 0.2 percentage by weight.

12. The bearing element according to claim 8, wherein the proportion of carbon ranges from 0.9 to 1.4 percentage by weight.

13. The bearing element according to claim 8, wherein some of said carbon is precipitated as fine carbon particles in the iron matrix alloy.

14. A bearing material, comprising: an austenitic iron matrix alloy consisting of: a proportion of sulphide-based solid lubricants; a proportion of carbides; at least one alloying element including cobalt, rhenium, tantalum, vanadium, hafnium, yttrium and zirconium having a cumulative weight percentage of 1 to 6; and a composition of the following alloying elements in addition to the at least one alloying element: carbon: 0.9 to 1.4 wt. %; chromium: 21 to 28 wt. %; manganese: 0.1 to 1.0 wt. %; silicon: 2.0 to 3.5 wt. %; nickel: 14 to 23 wt. %; molybdenum: 1.5 to 3.5 wt. %; niobium: 1.0 to 3.0 wt. %; tungsten: 2.0 to 3.5 wt. %; sulphur: 0.15 to 0.5 wt. %; copper: 1.0 to 3.5 wt. %; nitrogen: 0.1 to 0.8 wt. %; and iron with a remainder including unavoidable impurities.

15. The bearing material according to claim 14, wherein some of said carbon is precipitated as fine carbon particles in the austenitic iron matrix alloy.

Description

DETAILED DESCRIPTION

(1) In a preferred embodiment, the proportion of sulphur is at least 0.2% by weight, and the proportion of carbon is at least 0.8% by weight and at most 2.0% by weight. In fact, the preferred carbides are advantageously formed in an iron matrix with a carbon content as low as 0.8% by weight, thereby improving the solid lubricating properties, wear resistance and mechanical strength. In contrast, when the carbon content is above 2.0% by weight, the martensitic microstructure increases, an excessive quantity of hard, brittle cementite (Fe.sub.3C) is formed as well as excessive quantities of carbides, which are formed between the carbon and other alloy component, causing the iron matrix to become brittle.