Abstract
This study was carried out to easily evaluate thermal shock resistance of WC-Co based alloys at room temperature by YAG laser machining. Surface state and bending strength of the HIPed alloys with different Co content and WC grain size were investigated before and after introducing thermal cracks on the surface of the as-ground alloys by YAG laser machining which is considered to be similar to wire electric discharge machining (WEDM) in thermal shock.
The results obtained were as follows: (1) βWC1-x and W2C phases and also thermal cracks were observed on the laser-machined surface. The number of thermal cracks decreased with the increase of Co content in the alloy and it was fewer in micro grain alloy than in fine grain alloy. (2) Bending strength (σmG) before laser machining showed a maximum value in 12mass%Co alloy and it was larger in micro grain alloy than in fine grain alloy at the same Co content. On the other hand, the strength (σmL) after laser machining decreased with the decrease of Co content and remarkably decreased in micro grain alloy. (3) The strength ratio of σmL to σmG decreased with decreasing Co content and WC grain size, and also it showed a good correlation with the thermal shock damage resistance parameter of the alloy. The abovementioned results were almost the same as the cases of WEDM.
