炭化けい素セラミックスの曲げ強度と圧こん法による破壊じん性の評価

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Vickers hardness test,four-point bendung test fracture toughness evaluation by two kunds of indentation (ISB and IF methods)were conducted on reaction sintered and pressure-ledd sintered silicon carbide ceramics,SiC-R and SiC-PL.Thedependences of hardness Hv,bending fracture strenghtσ_f and fracture toughness K_<IC>, onthe indented load P were investigated.The effects of loading rate and atomosphere on the σ_f were also studied.The Hv decreased with increasing P for two SiC materials.The indented shapes were clear comparatively and four cracks initiated from vertices of the indentation for SiC-Pl. For SiC-R,however,a part of the indented surface peeled off by the sffect of lateral cracks initiated near the surface layer,and the fracture surface was not flat. For the smooth pecimens, the mean value of σ_f of SiC-PL was higher than that of SiC-R. For the specimens pre-cracked by Vickers indentation,σ_f decreased with increasing P for the both materials, and the mean value and the variation of σ_f for SiC-R was larger than those for SiC-PL. For SiC-R,the dependences of σ_f on the strain rate and atomospere such as in water and in silicon oil were not observed in the pressent experiment conditions.The K_<IC> bythe ISB method and by the IF method were almost identical in the same P condition.The K_<IC> by the IF method decreased with increasing P for SiC-PL.while the K_<IC> increased with increasing P for-SiC-RThis might be caused by peeling-off of the indented surface layer of SiC-R.
社団法人日本材料学会の論文
1990-07-15

炭化けい素セラミックスの曲げ強度と圧こん法による破壊じん性の評価

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