Wear resistant alloy for valve seat insert used in internal combustion engines

1. A martensitic wear resistant iron base alloy with excellent hot hardness and wear resistance comprising:

a) about 2.05 to about 3.60 wt % carbon;

b) about 3.0 to about 10.0 wt % chromium;

c) about 0.1 to about 3.0 wt % silicon;

d) about 0 to about 8.0 wt % cobalt;

e) about 11.0 to about 25.0 wt % of molybdenum;

f) about 0.1 to about 6.5 wt % nickel;

g) about 0.0 to about 8.0 wt % vanadium;

h) about 0.0 to about 6.0 wt % niobium;

i) about 0 to about 2.0 wt % manganese;

j) less than 0.5 wt % aluminum; and

k) the balance being iron and impurities,

l) wherein i) the alloy has been tempered from an as-cast condition so that substantially all residual austenite is changed to martensite, ii) the alloy contains alloy carbides embedded in a matrix of tempered martensite, the alloy carbides consisting essentially of carbides formed during solidification from casting a melt of the alloy composition, and; iii) the alloy is capable of having, after being heat treated at a temperature of 1200° F. for one hour and then liquid nitrogen chilled, a hot hardness ratio, defined as hot hardness at 800° F. divided by room temperature hardness, of at least 0.8219.

2. An internal combustion engine component comprising the alloy of claim 1 .

3. The alloy composition of claim 1 wherein the amount of carbon is between about 2.1 wt % and about 2.5 wt %.

4. The alloy composition of claim 1 wherein the amount of chromium is between about 6.0 wt % and about 10.0 wt %.

5. The alloy composition of claim 1 wherein the amount of silicon is between about 0.5 wt % and about 2.5 wt %.

6. The alloy composition of claim 1 wherein the amount of cobalt is between about 0 wt % and about 6.0 wt %.

7. The alloy composition of claim 1 wherein the amount of molybdenum is between about 14.0 wt % and about 18.0 wt %.

8. The alloy composition of claim 1 wherein the amount of nickel is between about 3.0 wt % and about 6.0 wt %.

9. The alloy composition of claim 1 wherein the amount of vanadium is between about 2.0 and about 6.0 wt %.

10. The alloy composition of claim 1 wherein the amount of niobium is between about 0.5 wt % and about 3.5 wt %.

11. The alloy composition of claim 1 wherein the amount of manganese is between about 0 and about 0.8 wt %.

12. The alloy composition of claim 1 wherein the amount of iron is greater than about 45.0 wt %.

13. A martensitic wear resistant iron base alloy with excellent hot hardness and wear resistance comprising:

a) about 2.05 to about 3.60 wt % carbon;

b) about 3.0 to about 12.0 wt % chromium;

c) about 0.1 to about 3.0 wt % silicon;

d) about 0.0 to about 8.0 wt % cobalt;

e) about 11.0 to about 25.0 wt % of molybdenum and tungsten, with the molybdenum content of the alloy being at least 11.0 wt %;

f) about 0.1 to about 6.5 wt % nickel;

g) about 0.0 to about 8.0 wt % vanadium;

h) about 0.0 to about 6.0 wt % niobium;

i) about 0 to about 2.0 wt % manganese;

j) less than 0.5 wt % aluminum; and

k) the balance being iron and impurities,

l) wherein i) the alloy has been tempered from an as-cast condition so that substantially all residual austenite is changed to martensite ii) the alloy contains alloy carbides embedded in a matrix of tempered martensite, the alloy carbides consisting essentially of carbides formed during solidification from casting a melt of the alloy composition, and; iii) the alloy is capable of having, after being heat treated at a temperature of 1200° F. for one hour and then liquid nitrogen chilled, a hot hardness ratio, defined as hot hardness at 800° F. divided by room temperature hardness, of at least 0.8219.

14. An internal combustion engine component comprising the alloy of claim 13 .

15. The alloy composition of claim 13 wherein the amount of carbon is between about 2.1 wt % and about 2.5 wt %.

16. The alloy composition of claim 13 wherein the amount of chromium is between about 6.0 wt % and about 10.0 wt %.

17. The alloy composition of claim 13 wherein the amount of silicon is between about 0.5 wt % and about 2.5 wt %.

18. The alloy composition of claim 13 wherein the amount of cobalt is between about 0 wt % and about 6.0 wt %.

19. The alloy composition of claim 13 wherein the amount of molybdenum and tungsten is between about 14.0 wt % and about 18.0 wt %.

20. The alloy composition of claim 13 wherein the amount of nickel is between about 3.0 wt % and about 7.0 wt %.

21. The alloy composition of claim 13 wherein the amount of vanadium is between about 2.0 and about 6.0 wt %.

22. The alloy composition of claim 13 wherein the amount of niobium is between about 0.5 wt % and about 3.5 wt %.

23. The alloy composition of claim 13 wherein the amount of manganese is between about 0 and about 0.8 wt %.

24. The alloy composition of claim 13 wherein the amount of iron is greater than about 45.0 wt %.

25. The alloy composition of claim 1 wherein the alloy has a sliding wear rate of no greater than 11.7mg, as measured at 800° F. using ASTM G99-90 pin-on-disk wear testing at a velocity of 0.13m/s for 255m.

26. The alloy composition of claim 13 wherein the alloy has a sliding wear rate of no greater than 11.7mg, as measured at 8000F using ASTM G99-90 pin-on-disk wear testing at a velocity of 0.13m/s for 255m.

27. A method of making a cast product of a martensitic wear resistant iron base alloy with excellent hot hardness and wear resistance comprising:

a) making an alloy melt comprising

i) about 2.05 to about 3.60 wt % carbon;

ii) about 3.0 to about 10.0 wt % chromium;

iii) about 0.1 to about 3.0 wt % silicon;

iv) about 0 to about 8.0 wt % cobalt;

v) about 11 .0 to about 25.0 wt % of molybdenum;

vi) about 0.1 to about 6.5 wt % nickel;

vii) about 0.0 to about 8.0 wt % vanadium;

viii) about 0.0 to about 6.0 wt % niobium;

ix) about 0 to about 2.0 wt % manganese;

x) less than 0.5 wt % aluminum; and

xi) the balance being iron and impurities;

b) casting the alloy melt into a mold and allowing the alloy to solidify under conditions that form alloy carbides and a solid solution strengthened matrix of martensite and residual austenite in the solidified alloy, wherein the alloy is capable of having, after being heat treated at a temperature of 1200° F. for one hour and then liquid nitrogen chilled, a hot hardness ratio, defined as hot hardness at 800° F. divided by room temperature hardness, of at least 0.8219; and

c) tempering the solidified alloy under conditions such that substantially all residual austenite is changed to martensite, and the tempered product contains alloy carbides embedded in a matrix of tempered martensite.

28. The method of claim 27 wherein the product is machined into a component for an internal combustion engine.

29. The method of claim 27 wherein the alloy is capable of having a Rockwell C hardness at room temperature that does not exceed 63.4 after being tempered at a temperature of 1200° F. for one hour.

30. The alloy of claim 1 wherein the alloy is capable of having a Rockwell C hardness at room temperature that does not exceed 63.4 after being tempered at a temperature of 1200° F. for one hour.

31. The alloy of claim 13 wherein the alloy is capable of having a Rockwell C hardness at room temperature that does not exceed 63.4 after being tempered at a temperature of 1200° F. for one hour.