Wear resistance of microporous coatings after abrasive treatment

The process of abrasive treatment of bearing journals of various shafts of agricultural machinery restored by application of microporous coatings on a nickel base is characterized by low technical and economic indices. The difficulties arising during grinding of these coatings are caused by their specific properties such as low thermal conductivity, presence of oxides and slags, high nickel content level in the coating, etc. We propose a new technology of abrasive treatment of microporous coatings on a nickel base that provides a significant increase of grinding efficiency of restored parts. The new technology is based on the use of optimal grinding modes with an abrasive tool with optimal characteristics and with the use of an effective composition of the grinding oil. To determine the operational properties of restored parts after their dimensional processing by grinding, the wear resistance of the built-up layers and their tribotechnical characteristics were evaluated. It was also necessary to compare the performance properties of the applied coatings with the performance of new shafts and shafts processed using other technologies. The paper describes a method of wear bench tests of highly loaded parts of automotive and tractor engines in the “crankshaft journal - plain bearing shell” coupling on an II5018 friction machine using the “disk - shoe” scheme as well as a method of quantitative wear evaluation of samples and counter-samples. The operating modes of the friction machine and the results of comparative wear tests are discussed, and the tribological characteristics of microporous coatings are presented. It is shown that a friction couple with a sprayed sample processed using the new technology had higher wear-resistance and better tribological properties as compared to a friction couple of a steel sample and a sprayed sample after processing using the old technology. However, the obtained results on wear resistance and tribological characteristics should be verified under normal operating conditions.