The Effect Of Alloying On Structural Stability And Properties Of Ti-Al-N Coatings

TiAlN is one of the most widespread used coatings in tool and die steels. But with thedevelopment of high speed cutting and dry cutting of the tool, it has become difficult to meetthe requirements of improving comprehensive mechanical property. So further improveTi-Al-N coatings with higher Al content in the comprehensive mechanical properties and hightemperature oxidation becoming an important development direction. In this paper, weprepared (Ti, Al, Si, Y) N coating which in the premise of high Al ratio on the W6Mo5Cr4V2high speed steel with multi-arc ion plating. Micro-hardness Tester, Nano Scratch Tester, X-rayDiffractometer, Scanning Electron Microscopy and Electronic Probe was used to characterizethe film surface and cross-section, micro-hardness, adhesive force, film structure andcomposition. The results prove that:（1） The number of targets has a great impact on the proportion of the large particles inthe plasma etching process, followed by the bias voltage and the target current. Two Titargets, working current with50A and bias voltage sequentially incremented from400Vto700V are the optimum arc cleaning processes for W6Mo5Cr4V2high speed steeladopted by this experiment.（2） The sputtering rate of the target (except the outer Al-4Y Alloy target) increasedlinearly with the target current. Component segregation in deposition process and unevenchemical composition in Al-4Y target results in the precarious sputtering.（3）(Ti, Al)N content with B4-ZnS’s structure increases with the Y increased in (Ti33Al67)1-xYxN,(Ti30Al70)1-xYxN and (Ti28Al72)1-xYxNcoating with a high Al content. Ti-Al-Ncoating structure changed from cubic structure to close-packed hexagonal phase owing tothe adding of Y. So Y is harmful to the stability of the coating structure.（4） The hardness and adhesive force are all increased with Si content raised in the(Ti33Al67)1-x-ySixYyN coating. While the growth-rate of hardness is smaller and adhesiveforce also declined with the increase of the content of Y. HV0.253550is the highesthardness when the content of Si is4%and Y is1.5%.21.74N is the maximum adhesiveforce when the content of Si is4%and Y is0%.（5） High temperature oxidation resistance of coating is improved through the added of Siand (or) Y. For one hand, Si and Y refined the grain. For another hand, alloying promoteAl atoms diffused outward and form the Al2O3oxide film, this will resist thecounter-diffusion, thus delay oxidation process. These two aspects result in theimprovement of oxidation.