WC-Co超硬合金の疲労き裂進展特性に及ぼす応力比およびWC粒径の影響

概要

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In order to study the influence of stress ratio and WC grain size, the characteristics of fatigue crack growth were investigated in WC-22wt.%Co cemented carbides with two different grain sizes of 3 and 6μm. Fatigue crack growth tests were carried out over a wide range of fatigue crack growth rate covering the threshold stress intensity factor range ΔK_<th>. The fatigue tests were conducted at 10Hz and two stress ratios R=0.1 and 0.5 in laboratory air at room temperature using the 3-point bending specimens. It was found that the crack growth rate da/dN against the stress intensity factor range ΔK depended on stress ratio R. The crack growth rate plotted in terms of the effective stress intensity factor range ΔK_<eff> (after allowing for crack closure) still exhibited the effect of microstructure. Fractographic examination revealed brittle fracture at R=0.1 and ductile fracture at R=0.5 in Co binder phase. The amount of Co phase transformation was closely related to the fatigue crack growth characteristics.
社団法人日本材料学会の論文
1997-12-15