| 摘要 |
PURPOSE:To suppress the scattering of the strength and improve the fracture toughness of the surface by executing the heat treatment of a composite sintered compact made of silicon nitride and silicon carbide, and grinding the surface. CONSTITUTION:The composite sintered compact of silicon nitride and silicon carbide in a cutting tool made of the composite sintered compact of silicon nitride and silicon carbide consists of the matrix phase made of silicon nitride and silicon carbide having fine structure where the particles of silicon carbide of <=1mum in average grain size are present in the grain boundary of the particles of silicon nitride and the particles of silicon carbide of several nm to several hundred nm in size are dispersed in the particles of silicon nitride, and the dispersed phase of the particles of silicon carbide of 5-50mum in average grain size, and/or the whisker of silicon carbide whose minor axis is 0.05-3.0mum in length and whose aspect ratio is 5-300. In addition, the oxide layer containing silica on the surface of the sintered compact and/or the layer with different hue from that of the inside part are provided. The heat treatment of this surface and the subsequent grinding suppresses the scattering of the strength of the sintered compact, the fracture toughness of the surface is improved, and similar effect to that of the coating can be obtained. |
