Structure of surface layers and wear resistance of quenched 50G steel after finishing, antifriction, nonabrasive treatment

The effect of the finishing, anti~ction, nonabrasive treatment (FANT) on the structure of the surface layer of the 50G steel subjected to quenching with rf heating without any friction is investigated. Ideas are formulated about the mechanism of formation of the surface layer. Structural parameters of the quality of the coatings determined by the method of nondestructive testing of the surface layers are presented, which can be used as criteria for rapid estimation of the conditions of technological surface treatment. The aggregate of tribotechnical properties of parts of cylindrical piston group including the wear resistance of linings, rings, and pistons, the coefficient of friction, breaking-in ability of the cylinder-lining--piston-ring pair, and the compatibility between the contacting metallic materials refer to factors that control the reliability and longevity of the internal-combustion engines. These properties can be estimated under service-, bench-testing-, and laboratory-testing conditions. A comparison between the results of laboratory tests using machines that produce reciprocating sliding with the wear data on linings and piston rings obtained during service [1 and others] showed that they were qualitatively in agreement, which indicates that it is expedient to estimate the tribotechnical properties in laboratory tests. These tests happen to offer unique possibilities for obtaining a separate estimate of the quality of a pair consisting of a cylinder--piston set needed for the substantiation of the approach toward the choice the structural and lubricating materials, the conditions of the technological processing of the surface parts leading to reduced losses by friction and wear. One of the methods of improving the tribotechnical properties of the parts of a cylinder--piston set is the brass plating or a finishing, antifriction, nonabrasive treatment (FANT) of the surface [2-4]. This treatment is also technologically simple, as well as effective in preventing seizure and decreasing friction and wear. However, according to the data of [4], depending upon the service conditions the effect of FANT may not even be manifest which gives us reaso~ to assume that a negative result is possible depending upon many factors, particularly the structural state of the treated material. Such cases were observed in practice during the service of internal-combustion engines. In this paper, based on the results of laboratory tests on the lining--ring friction pair, we have analyzed the changes in the structure of the surface layer of the quenched 50G steel subjected to FANT, their effect on wear resistance, as well the quality of the surface layer. Using a 77MT-1 reciprocating sliding-friction machine (at a pressure of 30 MPa and average velocity of 0.1 m/sec),