Dependence of Microporous Coating Grinding Indicators on Technological Factors

Abstract—Wear-resistant nickel-based gas-thermal coatings used to restore worn parts have long been recognized. However, these coatings are among the materials the abrasive machining of which poses some difficulty. The main cause for poor machinability of such coatings during grinding is caused by their specific physicomechanical properties resulting in faster wear of abrasive wheels. A method is proposed to increase the efficiency of the grinding process of deposited coatings by searching for optimum technological factors (cutting mode elements and characteristics of wheels, providing high technical and economical characteristics). The data of experiments on establishing the achievable values of machining productivity Q_m and wear rate Q_a of abrasive tools during cylindrical external infeed grinding of deposited coatings are presented. The dependences of the machining productivity and wear intensity of abrasive wheels on cutting modes, namely, the wheel speed, a part rotation speed, and radial feed speed and also on grinding tool characteristics (grain size, hardness), are studied. The methods and results of abrasive machining of deposited coatings according to the scheme of circular infeed grinding with the use of a fractional factorial experiment (FFE) are described. This work also presents the levels of technological factors and the ranges of their varying. The main calculation formulas are also given. The conditions of performing experiments are described, the choice of the types, sizes, and characteristics of grinding wheels are justified, and the chemical composition of gas-thermal deposited coatings under machining and the sizes of the samples are presented. The results of fractional factorial experiment are processed, linear mathematical models of the technological process have been obtained, and their adequacy has been verified. The obtained empirical dependences are analyzed, and a scientific explanation of the obtained results are given from the point of view of the cutting theory. The developed dependences can be used in the future to optimize the cutting conditions and the characteristics of grinding wheels according to a technological cost minimization criterion.