| In modern production, the mechanical parts are often required to work at high temperature, heavy load, dry and other harsh conditions, they often fail because of surface wear, corrosion or high temperature oxidation. Surface poor performance is one of the most important reasons for the failure of materials, the resulting loss is very marvelous. Bearing steel is always used as a machine bearings, ball bearings, bearing rings, etc., which is widely used in many places. As a carrier parts, its life play an important part in proper functioning of the entire system. According to the reliable datas from national authoritative department, the main failure modes of such steel are surface scratche, abrasion, wear, especially when working without lubricants, which is very serious. Improve its hardness, wear resistance, corrosion resistance and other properties will extend its service life, which can reduce costs for industrial production and create greater economic value. This paper is aimed at using magnetron sputtering deposits CrN and TiAlN coating on GCrl5 bearing steel wafers, and innovatively using High Power Impulse Magnetron Sputtering.This paper explored the effects of nitrogen flow ratio and substrate bias on the structure and properties of CrN coatings, and also explored the effects of nitrogen flow ratio and working pressureon TiAlN coatings, which were deposited by reactive magnetron sputtering. Using XRD, FESEM, EDS, AFM, Rockwell Hardness Tester, Micro Vickers Hardness Tester analysis the structure, composition, morphology, bond and hardness of coatings, obtain the optimized process parameters.CrN coatings research:(1) CrN coatings were deposited under nitrogen flow ratio (20%,30%,40%,50%) and substrate bias voltage (0,50V,100V,200V), which show columnar growth and mainly contain Cr, Cr2N and CrN. (2) With the increase of nitrogen flow ratio, the deposition rate decreases, the hardness first increases then decreases. When nitrogen flow ratio reaches 40%, the Cr, N atomic ratio is nearly 1:1, displaying triangular pyramid. The coating deposited under 40% is relatively good, with the deposition rate (0.69μm/h), good bond of coating/substrate, high hardness HVo.o1 up to 1752. (3) With the increase of substrate bias voltage, the deposition rate decreases, the hardness increases. The Cr, N atomic ratio remains nearly 1:1, regardless of the substrate bias voltage. The coating deposited under 50V is relatively good, with the deposition rate (0.53μm/h), good bond of coating/substrate, high hardness HV0.01 up to 2372.TiAlN coatings research:(1) TiAN coatings were deposited under nitrogen flow ratio (16%,20%,30%,40%) and working pressure (0.3Pa,0.5Pa,0.7Pa, 1.0Pa), which shows columnar growth and mainly contain Ti3AlN, AlN and TiN. (2) With the increase of nitrogen flow ratio, the deposition rate decreases, the grain size increases, the density decreases. The coating which deposited under 20%is relatively good, with small grain size (about 100nm), low roughness (1.508 nm), good bond of coating/substrate, high hardness HV0.01 up to 1302. (3) With the increase of working pressure, the deposition rate first increases then decreases, same as the grain size, the coating deposited under 0.5Pa is relatively good.In order to further study Coatings, CrN and TiAN coatings were deposited by DC magnetron sputtering and high power pulsed magnetron sputtering(HIPIMS) respectively based on the optimized process parameters. The coatings were tested under 1N,0.1 m/s without lubricants. The results:(1) The uncoated bearing steel exhibits high friction coefficient(about 0.75) and bad wear resistance. (2) The friction coefficient of CrN coating deposited by DC magnetron sputtering is 0.65, and 0.6 by HIPIMS. (3) The friction coefficient of TiAlN coating deposited by DC magnetron sputtering DC is 0.7, and 0.66 by HIPIMS. (4) The Evolution of friction coefficients of bearing steel with coatings display small fluctuation comparing with uncoated. |
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