WC-Co超硬合金の曲げ破壊強度に及ぼす研削加工の影響(<小特集>先進材料と信頼性解析・評価)

概要

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The three-point bending test was conducted on ground specimens (30×8×4, mm) of a commercial WC-Co alloy having four different surface roughnesses with R_<max> of 3.0, 0.3, 0.1 and 0.03 μm. It was found that the bending fracture strength and its scatter were almost the same in all specimens irrespective of surface roughness, except for exceptionally low strengths obtained in a few specimens with R_<max> of 0.03 μm. This negligible effect of grinding on the strength was explained by assuming that the two effects of surface roughness and compressive residual stress measured in this study cancelled each other. In addition, it was proposed that the grinding process generally "healed" relatively large surface defects, and this "healing effect" resulted in the increased strength. The exceptionally low strength of a few specimens of R_<max> 0.03 μm is principally caused by lack of the healing effect.
1995-09-25