| 摘要 |
PURPOSE:To obtain high hardness and sufficient toughness, by forming the seated part of an exhaust valve into composition such that fine particles of hard quality like chrome boride, chrome carbide, etc. are uniformly dispersed in a matrix of Ni-system. CONSTITUTION:A base structure 1 in an exhaust valve uses heat-resisting steel of austenite-system silicon-chrome steel, stainless steel, etc., and a seated part 3 peripherally provides a recessed groove. The recessed groove is degreased, applying Ni plating to thickness about 10-20mu by electrolytic plating. The inside of the recessed groove is filled with metallic powder 3, forming a sintered layer by the HIP method or hot press method. The metallic powder is composed of 8- 20% Cr, 1.5-4.0% B, 2.0-6.0% Si, 0.1-1.0% C and the rest of Ni, increasing hardness by Cr, B, C crystallizing a hard particle to be separated while lowering a melting point by B, Si. |
