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United States Patent 5935350
Douris , ê et al. August 10, 1999

Hardfacing method and nickel based hardfacing alloy

Raghu , Ê et al. August 10, 1999

Abstract

A nickel based hardfacing alloy having the following elemental constituents, by weight: Cr, 16-22%; Mo, 1-7%; Si, 2.5-3.7%; C, 0.8-1.4%; B, 2-3%; Fe, 2-3.9%; Co, 4.3-17%; Ni and incidental impurities, balance. The alloy is in gas-atomized powder form suitable for deposition by plasma transferred arc welding, has a hardness in the range of about 50 Rc to 60 Rc, a coefficient of friction in the range of about 0.12 to 0.13, an ASTM G-65 wear rating in the range of about 20 to 26, and an ASTM G-77 wear rating in the range of about 0.0 to 0.074. A method of enhancing the abrasive wear resistance and metal-to-metal wear resistance of a substrate by welding a Ni based alloy having at least 40% Ni by weight, between 4% and 18% Co by weight, and between 2% and 3% B, onto wear surfaces of the substrate as a coating having a thickness between about 0.025 in. and about 0.5 in. A plastic extruder screw comprising a metallic body having screw flights and a coating on the screw flights, which coating is between about 0.025 in. and 0.5 in. thick, and is a Ni based alloy having between 4% and 18% Co by weight and between 2% and 3% B by weight.