The ratio of coated cemented carbide tools in metal processing industry is increasing steadily. In recent 10 years, its quality and performance have been significantly improved. On the one hand, due to the quality improvement of the coating , it will be better to control porosity and thickness; on the other hand, the metallurgical technology between the coating and the substrate interface has also been improved, therefore can increase the adhesion of the coating and prevent the interfacial reaction that reduces the strength. Increasing cutting speed can significantly improve productivity, and the use of coated tools is the most effective way to reduce costs.
Coated cemented carbide tools has different performances under different coating thicknesses. The following is the changes in crater wear and subsequent wear:
1.0 The wear resistance of the crescent crater is directly proportional to the thickness of the coating and has great relationship with the composition of the coating. The coating can improve the wear resistance of the crescent crater. When the depth of the crescent crater exceeds the thickness of the coating, the wear rate of the crescent crater increases significantly. However, even after the coating is broken through, the coating around the crescent crater can delay the crescent crater in some way according to the hardness of the coating.
2.0 When the thickness of the coating exceeds the minimum value of 5~9μm, the wear resistance of the rear is no longer affected by the thickness of the coating. When the coating is broken through, the subsequent wear rate does not increase. The critical zone of rear wear seems to be only in a narrow range at the bottom of the rear wear scar. In order to improve the wear resistance of the back, just cover this area with a coating. Between the blade and the work piece, the coating reduces the wear speed, so the coating improves the wear resistance of the rear. With the increase of cutting speed, chemical wear is playing more and more important role. Therefore, coatings with good wear resistance such as tic are suitable for low speed cutting, while those with high chemical stability are suitable for high speed cutting.
