The influence of
thermal shock on bending strength,
fracture toughness and hardness of 3540 and 3475
cemented carbide was investigated.The results show that,with increasing of the number of thermal shock,
flexural strength and fracture toughness of the cemented carbides increase firstly and then decrease,and their hardness decrease.This is ascribed to the combined effects of the restraint of fcc γ→hcp γ phase transformation due to quenching,solid solution strengthening of bonding phases,increasing of mean free path of γ phase,and thermal stress of thermal shock.After thermal shock the roughness of fracture surface of 3540 and 3475 cemented carbides decrease,and their pores and intergranular crack increase.
Oxidation occurs on the surface of alloys after thermal shock,resulting in the formation of loose oxidation layer.The oxidation resistance of 3540 cemented carbide is better than that of 3475 alloy.It is observed that the carbon in carbon gathering regions diffused resulting in the formation of pores and small cracks at WC/Co interface.
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