Preparation And Performance Of Tin Composite Coatings And(Ti,Cr)N Coating

TiN,Ni-W+TiN,plasma nitride+TiN and （Ti,Cr）N coatings were deposited by arc ionplating on H13and W6substrates. The surface and cross section morphology, distri-butions of the chemical elements,hardness and phase compositions of coatings were anal-yzed by the means of scanning electron microscopy（SEM）,Energy Dispersive Spect-rometer （EDS）, micro-hardness tester and X-ray diffraction（XRD）. Wear tester was usedto test the wear resistance of the fou coatings. Corrosion characteristics of TiN,Ni-W+TiN,Plasma nitride+TiN coatings in3.5%NaCl were examined by the electrochemicalworkstation.And the corrosion resistance of （Ti,Cr）N coating in3.5%NaCl and0.5MH₂SO₄was also tested by the electrochemical workstation. The high temperature oxidationbehavior of （Ti,Cr）N coating was tested with resistance furnace and the oxidationmechanism was studied. The main research results are as follows:（1） Dense and high binding force TiN，Ni-W+TiN，PN+TiNcomposite coatings and（Ti,Cr）N coating were successfully prepared by ion plating technology, brush platingtechnology and ion nitriding technology.The phase structure of TiN and （Ti,Cr）N coatingswere both fcc of NaCl. The composite coating can improve the distribution of hardnessand binding force of the coatings, to obtained a larger hardening interval.The hardness andbinding force of （Ti,Cr）N coating were higher than TiN coating.（2） All the four kinds of coatings can improve the abrasion resistance of thesubstrates,and the wear resistance of composite coatings and （Ti, Cr） N coatings are betterthan TiN coating. The wear mechanism of the coatings is abrasive wear with a smallamount of fatigue wear.（3） In the NaCl solution, the corrosion resistance of the coatings were greatlyimproved compared to the substrates. The coatings mainly play a role of mechanicalbarrier without passivation phenomenon occurring. The electrochemical corrosion of thecoatings were mainly as the result of holes in the coatings. The corrosion resistance of thecomposite coatings and the （Ti,Cr）N coating were better than the TiN coating, which ismainly due to the more defects on the surface of the TiN coating. With the existing of thetransition layer of composite coatings and Cr atoms joined in （Ti,Cr）N coating,the defects such as pinholes can be reduced, so that the structure of the coatings were more dense andthe corrosion resistance can be enhanced.In the H₂SO₄solution, passivation phenomenon occurred to the substrate and（Ti,Cr）N coating,but the break potential of the coating was higher than substrate by200mv.the passive current just equals to the1/6—1/17of substrate,so the corrosion resistance hasbeen greatly improved.（4）（Ti,Cr）N coating had well oxidation resistance below750℃and geted failure at800℃.（Ti,Cr）N coating can formed a bilayer structure. The top oxide layer consists of aTi-rich Ti-Cr mixed oxide. Below this layer, Cr is strongly enriched and a correspondingdepletion of Ti is obtained.The bil-ayer structure can effectively inhibit the O atomsinward diffusion and Cr atoms outward diffusion, so the coating had a better antioxidant.