Study On Industrial Preparation And Thermal Stability Of Cr-based Composite Nano-hard Coatings

Cr-based composite nano-hard coating,with characteristics such as high hardness,good film-based binding,wear resistance and high temperature resistance and other characteristics,are widely used in various types of cutting tools,hot molds and auto mobile components and parts and other fields.But the promotion of plated product’s working life various with the coating types.In the case of hot work die,the comprehensive performance of a variety of Cr-based composite nano-hard coatings around high temperature annealing and the effect of using various hot work molds were contrasted to select a coating which has the best comprehensive performance and improves effectively the various hot die’s working life,It is more conducive to the development of China’s manufacturing industry.In view of the failure of the hot die,CrTiAl SiCN gradient coating,CrTiAlN and CrTiAlSiN multi-component coating,CrAlN,Ti AlN,CrAlN（electromagnetic）and TiAlN（electromagnetic）ternary coating,were prepared by using a variety of processes of arc ion plating industrial preparation in this paper.The changes of the performance of each group were analyzed in detail before and after high temperature annealing.It mainly includes that the pretreatment methods and preparation techniques of various PVD coatings were summarized.The hardness,binding force,microstructure and phase structure of the coatings were analyzed before and after high temperature annealing.The molds of aluminum die-casting molds（3Cr2W8V）,cold stamping dies（Cr12MoV）and hot forging dies（4Cr5MoSiV1）were prepared and their service life were tracked.The conclusions are drawn as follows:The hardness of CrTiAlSiCN gradient coating is essentially constant,and the bind force decreased after different high temperature annealing.The formation of Al₂O₃,TiO₂ and Cr₂O₃and other oxides not only reduce the surface friction coefficient,improve the wear resistance of the coating,but also prevent continuous oxidation since O₂ is in contact with Ti element inside the coating,and improve high temperature oxidation resistance of the coating.After CrTiAlSiCN coating was deposited on the surface of the aluminum die-casting mold,cold stamping die and hot forging die,the working life of the mold have been significantly improved,which is the most significant cold stamping die.Its working life is 4.25 times higher than uncoated mold.Compared with CrTiAlN coating,the doping of Si element in CrTiAlSiN coating makes the grain refinement and compactness of the coating enhance,and also increases the internal stress of the coating,resulting in high hardness,high wear resistance and high temperature oxidation resistance of the coating,but the bonding force is slightly worse.After CrTiAlN and CrTiAlSiN coatings were deposited on the surface of the three hot molds,CrTiAlSiN coating of the cold stamping die is better to improve the working life than other coatings.Its working life is 4 times higher than uncoated mold.The CrAlN（electromagnetic）coating,using ring type magnetic filter coil preparation,has high hardness and good binding force.The surface friction coefficient of coating is low and the wear resistance is good.Al₂O₃ and Cr₂O₃ are formed on the surface of the coating after annealing,which prevents the formation of TiO₂ and has excellent oxidation resistance at high temperature.After CrAlN（electromagnetic）and TiAlN（electromagnetic）coatings were deposited on the surface of the three hot molds.CrAlN（electromagnetic）coating on the cold stamping die effect is most significant.Its working life is 10 times higher than uncoated mold.Compared with all coatings in this paper,the comprehensive performance of CrAlN（electromagnetic）coating is not only better than the other three kinds of three element coating,but also has obvious advantages compared with the traditional gradient coating and multi-component composite coating.