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

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.

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.