MATHEMATICAL MODEL FOR THE FORMATION OF RESIDUAL STRESSES IN COATINGS DURING PLASMA SPRAYING WITH FLUSHING
The article presents the results of studies of residual stresses in coatings applied by plasma sputtering with reflow. Analytical dependences have been obtained showing the effect of residual stresses in coatings on the strength of their adhesion to the substrate and on their basis a refined mathematical model has been proposed that establishes the regularities of the influence of temperature-time parameters of plasma reflow on the level of residual stresses. The results of mathematical modeling of the formation of residual stresses in plasma coatings, taking into account the time and temperature of their melting are presented. The equations allowing to estimate dynamics of change of temperatures of a covering and the restored detail by means of which it is possible to estimate dependences of tangential stresses on thickness of the applied coverings are received. At the same time, the calculation error varies in the range of 7-10%. Based on the revealed regularities of the physical, mechanical and operational properties of plasma coatings, a mathematical model of the distribution of residual stresses at the «part-coating» interface has been developed. The numerical study of residual stresses in plasma coatings was carried out on the basis of the developed software complexes «Plasma Expert» and «Protection», which open up wide possibilities for a finite element description of the investigated system «coating-restored part». It is theoretically and experimentally proved that at optimal values of the main technological parameters and modes of plasma spraying, the reflow process can significantly reduce the internal residual stresses in coatings and increase their wear resistance.