Process Optimization Of CVD-TiN And Study On Its Properties

In the mold industry, the service performance and service life of cutting tools and drill bitswere highly demanded, and chemical vapor deposition method as a kind of special surfacestrengthening technology has been widely applied in this field. Cemented carbide was alwaysused as base material for chemical vapor deposition, because of its good thermal conductivity,high temperature stability and so on.In this paper, new technologies were used to deposit TiN hard films on YG6cementedcarbide substrates on the basis of the original deficient process. The component and mainperformance of TiN thin films deposited by new technologies were tested by X ray diffraction,scanning electron microscope, metallographic microscope, hardness tester and scratch test.Then, optimal process parameters were got by orthogonal experimental consequence.The XRD spectrum analysis showed that, besides TiN and WC phase, TiCxNy anddecarburization phase could be found in the films. It indicated that during the TiN depositionother side Reaction occurred, that could change not only the chemical composition, but also themicrostructure of TiN coatings, consequently affected the performance of the films. It could beconcluded that CVD-TiN coatings in these experiments exhibited the growth towarded apreferred (220) orientation by comparing each diffraction peak intensity of variouscrystallographic plane on the XRD patterns.The micro-morphology observed by SEM showed that, the films had rough surface, andstar-shaped and pyramidal structure can be seen on these coatings. The morphology exhibitedstar-shaped crystals at985℃, then changed from small pyramidal crystals at1015℃to largepyramidal and polyhedron crystals at1050℃. The fracture morphology of coatings showed that,the coating tissue, related to the preferred (220) orientation, were perpendicular to thesubstrate.The EDS analysis showed that, the N/Ti ratio of these coatings changed slightly at variousprocess parameters, but were all closed to1. Summarized all the performance test results, thehardness of TiN coating was up to2209HV, although the lowest hardness is only1403HV, themajority of hardness value reached2000HV. The cohesion value most at70N, these films,which had a thickness between7and9μm, had the best cohesion value. After high temperaturetreatment, bending strength decreased significantly about30%.The optimized process parameters were obtained by orthogonal analysis and rangeanalysis. Repeated test showed that, the optimized process was stable; the cutting experimentsshowed that, the service life of these samples prepared by optimized process can beimproved2~3times.