PURPOSE: To increase the life of a tool for Al-Si alloy and printing board work by providing a coating layer of diamond of more than 0.1μm on a base body consisting of sintered body of Si3N4 including MgO, etc., by 0.01W30wt.% totalling less than 50wt.%.
CONSTITUTION: The base body of sintered body of Si3N4 has a higher rigidity than an ultra-rigid alloy and a good abrasion resistance, and it has an almost similar linear expansion coefficient to diamond, so residual stress is not generated at a coating layer, so a coating layer having a good attachment property can be formed if the layer thickness is more than 20μm. However, the layer thickness of less than 0.1μm is not effective, or that exceeding 200μm is uneconomical. Though Si3N4 has a bad sintering property, a sufficiently dense and rigid sintered body can be obtained by adding at least one of MgO, Y2O3, Al2O3, AlN, a high temperature resistance is improved by adding ZrO2, HfO2, an abrasion resistance is improved by adding TiC, TiN, B4C, BN, TiB2, where the quantity of addition shall be within a range of 0.01W30wt.% for each, and if the total exceeds 50wt.%, the strength of Si3N4 sintered body is decreased.
MORIGUCHI HIDEKI
NOMURA TOSHIO
