Highly wear resistant coated engine tappet

摘要

A highly wear resistant engine tappet (5) has either (a) a sintered coating produced from a mixture of a binder, comprising (by wt.) 50-100% nickel powder, 0-45% Cr, 0-35% Mo, 0-10% Al, 0-25% Co, 0-10% Cu and impurities, and hard carbide, nitride and/or boride particles; or (b) a coating of an alloy of composition (by wt.) 44-88% WC, 4-10% Co, 15-50% Ni, 5-20% Cr, 0.5-4% B, 2-4% Fe, 0.5-4% Si, up to 1.0% C and impurities. Also claimed are methods of producing a highly wear resistant engine tappet by (i) press moulding a prepared mixture of a binder and hard particles, subjecting the moulding to primary sintering, subjecting the sintered body to secondary sintering onto the tappet surface to form a sintered layer and rapidly cooling the sintered layer under pressure to achieve a high surface hardness; or (ii) coating the tappet surface with the alloy composition as described in (b) by hot spraying and then remelting the coating.