Effect Of Nb And V Alloying On Microstructure And Properties Of AlCrN Coating

Under the constraints of economic factors and environmental protection requirements,tool coating is developing towards high performance,multi-type and environmental protection.Therefore,AlCrN-based coatings with better oxidation resistance and self-lubricating properties have become the pursuit of researchers.In this paper,based on the idea of multiple alloying,AlCrN coating was taken as the research object.Nb alloying is used to improve the high temperature oxidation performance of the coating.V alloying is used to improve the friction and wear properties.Nb and V co-alloying was used to provide AlCrN coating with the benefits of adding Nb/V separately.It is hoped to analyze the relationship between Nb and V elements on the microstructure and properties of coatings,and prepare self-lubricating hard coatings with high oxidation resistance.The main research achievements are as follows:（1）AlCrN coatings were alloyed with different contents of Nb.Attributed to the grain refinement effect of Nb,the fracture of the coating presents a dense fine structure,and there are many lattice defects inside the grain.When Nb content is 9 at.%,the coating exhibits the strongest adhesion,the highest hardness（36.1 GPa）and elastic modulus（384.4 GPa）.The wear rate of Al_0.63Cr_0.28Nb_0.09N is the lowest of 1.94×10^-7 mm³/（N·m）,and its oxidation resistance temperature can reach 1000℃.（2）AlCrN coatings were alloyed with different contents of V.Compared to the base AlCrN coating（H:27.2GPa;E:349.5GPa）,the addition of V helps to improve the mechanical properties of the coating（H:35.3 GPa;E:407.5 GPa）.But the introduced V forms soft VN phase.As the coating surface is rougher,the friction coefficient of V-containing coatings are slightly higher,but the wear rate are reduced.Amoung them,Al_0.67Cr_0.3V_0.04N shows the best wear resistance for the lowest wear rate(2.71×10^-7 mm³·N^-1·m^-1)and narrowest wear track.（3）Nb and V co-alloying AlCrN coatings with two ratios of Nb to V were prepared.Both coatings are mainly composed of c-AlCrN and show a strong preferred orientation along the（200）plane.The structural affects the performance,the co-alloying improve the cracking and plastic deformation resistance of AlCrN coating as well as the adhesion（79.5 N）.The synergistic effect of Nb and V significantly improves the tribological behavior of the coating in dry friction tests.When Nb/V=1:2,the friction coefficient of the coating is the lowest of 0.392;When Nb/V=9:4,the wear rate is the lowest of 1.42×10^-7 mm³/（N·m）.It also postponed the onset temperature of oxides from 800℃(Al_0.6Cr_0.28V_0.08Nb_0.04N)to 1000℃（Al0.59Cr0.28V0.04Nb0.09N）.