| Oxidation-induced strengthening in ground silicon carbide (2006) | |||||||||||||
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| LETTER Oxidation induced strengthening ground silicon carbide Chu Cho Sarkar Basu Yoon Park Received August Accepted February Springer Science Business Media LLC Silicon carbide has speci advantages over other struc tural ceramics such high temperature capability and excellent chemical stability silicon carbide prom ising candidate for high temperature structural materials well for corrosion resistance applications Like brittle materials however strength silicon carbide closely related the size and distribution surface aws such machining induced cracks because their inherent low toughness Thus smooth polishing procedure after grinding often needed order reduce the size surface aws leading increase cost ceramic components Moreover the allowable aws ceramics are small that almost impossible detect the aws and also dif cult remove them completely using machining techniques result the structural integrity ceramic component seriously affected method heal crack could considered overcome this problem Studies crack healing have been reported for alumina silicon nitride silicon nitride silicon carbide composite Mullite silicon car bide composite and silicon carbide Our research group recently proposed mechanism crack healing and strengthening pre oxidation procedure silicon carbide The major observation that the residual stress produced the thermal expansion mismatch between silica within cracks and surrounding silicon carbide played signi cant role the strength increase the crack hea. The strength enhancement of non-oxide structural ceramics (carbides, borides etc) has always been a major challenge. To this end, the effect of pre-oxidation on strength of silicon carbide with ground surface, machined using diamond wheels with varying grit sizes of 127m, 64 m, 42 m, 32 m, was investigated. The experimental results showed that the room temperature strength of ground specimens was improved because both grinding-induced-cracks and pre-existing surface flaws were healed during oxidation in air. After heat-treating, the strength measurements indicated a constant value of about 470 MPa, independent of the surface condition. Moreover, the strength remained almost constant up to 14000C, when the ground specimen was heat-treated at 15000C for 50h in air. | |||||||||||||
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