PHYSICAL-MECHANICAL CHARACTERISTICS AND THERMAL STRESS OF PLASMA COVERING

Purpose. It is based on the method of determining the physical and mechanical characteristics and cohesive strength of the plasma coating. Research methods. Experimental research methods of plasma coating specimens and mathematical methods of the theory of strength of materials. Received results. The study of the mechanical properties of the ПРНХ15СР2 plasma coating during the bending test was carried out. Values of forces and moments of elastic forces during bending depending on the deformation of the plasma coating sample was determined. The dependence of the destructive stress on the relative deformation of the coating was calculated. The modulus of elasticity and strength for the outer and inner surfaces of the coating are determined. Scientific novelty. It is shown that when determining the mechanical characteristics of the coating bonded to the base, a systematic error occurs due to the uncertainty of the internal stress in the coating. Therefore, for measurement, it is proposed to use samples peeled from the base, which are practically devoid of internal stress. For the inner surface of the coating, the modulus of elasticity and the destructive stress are rather higher than for the outer surface. The detected difference is associated with the presence of a temperature gradient during coating application and the distribution of residual stresses over the thickness of the coating. The gradient of residual thermal stresses and the maximum permissible temperature in the process of the coating deposition are determined. Practical value. The obtained results are of practical value for determining the conditions of guaranteed preservation of the integrity of the coating in the presence of residual stresses and calculating its maximum thickness on the base surface. It is shown that when the power of the plasmatron is reduced, the thermal stress gradient and the maximum stress on the coating surface decrease. Therefore, it is recommended to use a wire instead of a powder plasmatron, which twice reduces thermal stresses by half.