Tribological Mechanism And Applied Research Of Nickel-based Alloy Coatings On Automotive Gear Shafts By Plasma Spraying

In order to ensure the safety and reliability of the automobile,the Ni60-alloy with higher microhardness and wear resistance was sprayed on the surface of the easy-to-failure automobile gear shaft and the Mo / TiB₂,Co and Cr powders were infiltrated into the wear-resistant coating by the plasma spraying.The experiment and design were carried out with the uniform design of three factors and six levels.For the heat treatment on the surface of shaft material--low carbon alloy steel20 CrMoTi,the Ni60-based Mo,Co and Cr alloy coating with thicknesses of 200?m,400?m and 600?m by plasma spraying was prepared.And on the surface of the medium carbon steel 35 CrMo,it was prepared by the Ni60-based TiB₂,Co and Cr alloy coating with thicknesses of 200?m,400?m and 600?m.The microhardness of the alloy coatings were measured by the HV-1000 Hardness Tester.The wear experiment was implemented on the coating surface by the M-200 Abrasion Testing Machine under the following test conditions: lubrication with the L-AN15,loading the force with 10 N,the total wear time was 100 min?20min / time?,the rotate speed was 200 rad / min.The SEM and EDS were applied to the morphological and elemental analysis of the coating's profile and wear surface.The test result was simulated,optimized,predicted and analyzed by the Artificial Neural Network.Based on the predicted result,the verification test was carried out.The result shows: When the coating thickness of Ni60-based molybdenum /titanium diboride,cobalt,chromium alloy was 200?m,400?m and 600?m respectively,the two types of alloy coating's microhardness were within 716.2HV-1577 HV /915HV-1497.3HV,857.8HV-1661.6HV / 799.4HV-1322.9HV and 688.1HV-1234 HV /773.6HV-955.9HV respectively.The coating's wear extent was within 0.0027g-0.0282g/ 0.0024g-0.0919 g,0.0024g-0.0273 g / 0.0039g-0.0603 g and 0.0043g-0.0571 g /0.0043g-0.0571 g respectively.When the microhardness of the two matrixes 20 CrMoTi /35 CrMo was 372 HV / 481 HV and the total wear extent was 0.0226 g / 0.0358 g,the microhardness of the Ni60-based Mo / TiB₂,Co and Cr alloy coating was 1.9-4 times /1.9-3.1 times,2.3-4.4 times / 1.6-2.1 times,and 1.8-3.3 times / 1.6-1.9 times respectively of the matrixes;and the wear resistance of the coating was 0.8-8 times /0.4-14 times,0.8-9 times / 0.6-9 times and 0.9-3.3 times / 1.6-1.9 times respectively of the matrixes.The two types of coating have better comprehensive properties when theirthicknesses were 400?m / 200?m,respectively.The two coatings have layered structure and good bonding with the 20 CrMoTi / 35 CrMo.The wear mechanisms of the two kinds of coating mainly were adhesive wear,surface fatigue wear and abrasive wear.The formation of oxides,carbides and metal passivation can effectively improve the comprehensive properties of the coating in the process of plasma spraying.Comparisons between the results of the validation and the predicted values of the Artificial Neural Network were: when the thickness of the Ni60-based Mo,Co and Cr alloy coating was400?m,the error of microhardness was within 20%,and the error of wear within 15%.When the thickness of the Ni60 based TiB₂,Co and Cr alloy coating was 200?m,the error of the microhardness was within 11%,and the error of wear within 12%.The relative errors between the actual measured value and the predicted value of two kinds of coating were in the allowable range.Therefore,the Artificial Neural Network could be utilized to provide the rule set between the ratio of elements and the microhardness and wear extent of Ni60-based alloy coatings,and used to establish the ternary regression equation which then can be used to select the Ni60-based Mo / TiB₂,Co and Cr alloy coating with good comprehensive properties.This method is of important significance for energy conservation,environmental protection,life improvement of automotive gear shaft and traffic safety.