| Coating has often been cited as the effective way to improve the mechanical properties and service life of cutting tools; however, different coatings have different properties, wear mechanism and application condition. How to choose appropriate service condition is very important. In this paper, CrN, CrTiAlN, GLC (Graphite like carbon) coatings were deposited by Closed Field Unbalanced Magnetron Sputter Ion Plating. The morphology, microstructure of three coatings were studied by SEM and XRD. The basic mechanical properties such as hardness, adhesion strength were tested. The wear mechanism of three coatings in different loads and counterparts were studied by pin-on-disk device. Finally, application range of three coatings was given in this paper.Some significant results were obtained as follows: The main wear mechanism of CrN coating in lower load was surface fatigue wear. The friction surface would form oxide protection films of Fe and Cr as the load increasing. In higher load, gradual increasing compression stress resulted in the oxide films spalling and the coating failure, therefore, CrN coating wasn’t suitable in high load due to its poor adhesion strength. CrTiAIN coating had highest hardness, adhesion of coating and substrate as well as excellent thermal stability among three coatings, at the same time, content of Cr element in the coating made sure that CrTiAlN coating maintained the merit of forming oxide protection of CrN coating, therefore, no matter CrTiAlN coating sliding against steel or nonferrous metal counterparts, it had better tribological properties than CrN coating. When GLC coating sliding against GCr15 steel ball, it showed good tribological property because the friction coefficient of GLC coating decreased as the load increasing and its weight loss ratio was the least among three coatings. During the pin-on-disc test of GLC coating against Al and Cu nonferrous metal counterparts, there were few adhesion phenomenon, therefore, the tribological property was well. Compared with the other two coatings in the same experiment condition, lower friction coefficient of GLC coating made frictional heat reduced greatly. But the limited application factor of GLC coatings was its poor thermal stability.The main wear mechanism of hard wear resistant coatings in lower load was surface fatigue wear. Coating-to-substrate interface was the weak spot of wear system in higher load, so increasing adhesion strength would improve the service performance of coating. If there were Cr or Al elements which will form oxide protection films during friction process exiting in coating, wear resistant property of the coating would be improved. Antifriction coatings showed good wear resistant property because they would decrease frictional heat of frictional surface so that reduce oxidative phenomenon. |
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