| Adhesion strength and microhardness of (Ti_(1-x)Al_x)N coatings made by plasma enhanced chemical vapor deposition technique were investigated and the effect of heat treatment was characterized. The critical load of the (Ti_(1-x)Al_x)N coating to substrate was higher than 50N for X<0.15 and it decreased below 10N for X>0.15. Using 0.5 ㎛ thick TiN interlayer beneath (Ti_(1-x)Al_x)N coating, the adhesion strength could be improved. The residual chlorine content in the coating degraded the Knoop microhardness from 6500 to 1500 ㎏/㎟. The heat treatment at 1000℃ increased the microhardness due to the removal of the residual chlorine and the AlN precipitation. Residual stress of the coating from the difference of thermal expansion coefficient caused crack in coated layer, which was beneficial to improve the adhesion strength. In TiN and (Ti_(1-x)Al_x)N/TiN coatings, however, crack could not be observed after heat treatment, and the adhesion strength of the films did not change either. |
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