PHYSICAL AND MECHANICAL PROPERTIES AND WEAR RESISTANCE OF CRN/ALN SYSTEM COATINGS DEPOSITED BY MAGNETRON SPUTTERING

Abstract

The paper presents the results of investigation of CrN/AlN system coatings obtained by magnetron-ion reactive sputtering. Coating versions with a periodic nanocomposite structure with a layer period L = 1,5÷3,2 nm and a relative Cr content in the Cr/(Al + Cr) coating range of 68–85 % are studied. It is found that the coatings have a dense morphology and a columnar grain structure, which is typical for them. For all the samples, diffraction maxima corresponding to the cubic lattice are observed, being a superposition of the two compositions of CrN and AlN coatings. No peaks corresponding to AlN with a hexagonal structure type are recorded. Neither CrAlN peaks are found, that means that no homogeneous coating is formed. Experimental studies of the microhardness, modulus of elasticity, plasticity index and wear resistance of coatings obtained under different spraying conditions are conducted. Measurements showed that the microhardness and modulus of elasticity of the coatings obtained vary between H = 32÷42 GPa and E = 350÷420 GPa, respectively. The maximum plasticity index value H/E = 0,115 is reached at L = 3,2 nm, which corresponds to the coating versions with the greatest hardness. However, the H/E = 0,1 values are also fairly high with a minimum layer period (L = 1,5 nm) and a high Cr content. Abrasive wear coefficients of the coatings obtained vary in the range kс = (2,0÷2,8)·10–13 m3/(N·m). The minimum values of wear are reached at the maximum period of coating layers, i.e. with the greatest hardness, which agrees well with the classical theory of wear. At the same time, high wear resistance is observed at a low L, which indicates a correlation of the values of H/E and kс. Based on the experimental data, a group of neural network models is built that establish the relationship between the deposition process mode parameters (current on magnetrons) with the elemental composition of coatings, as well as the period of coating layers and relative chromium content with the physical and mechanical properties and abrasion resistance of CrN/AlN coatings.