ANALYSIS OF FIRMNESS CHARACTERISTICS OF ELECTRIC-SPARK COATINGS
The analysis of discrete electric-spark coatings with a density of 60% by sclerometric method is carried out. The influence of coating hardness on the propagation of deformation processes in the near-surface layers of the base material along the depth, and different degree of inhomogeneous plastic deformation along the length of the indenter scan route are established. The formation of electric-spark coatings with Cu, BK8+Cu, BK8 ensures a reduction of spread of deformation processes in the near-surface layers of metal at a depth of 20%, 70% and 95%, respectively. It is established that the deformation-firmness characteristics of the near-surface layers of metal play a key role in ensuring wear resistance of contact surfaces, given that acceleration / deceleration of the formation of the dislocation structure during friction is due to the activation of friction pairs. The evaluation of the firmness characteristics of discrete electric-spark coatings during friction established the influence of microhardness of the surface and near-surface layers of the material, the gradient of mechanical properties in depth and the integrity of the coating on their optimal structural suitability. Formation of combined electric-spark coating BK8+Cu eliminates the disadvantages that are identified for each coating separately. The presence of copper on the hard surface provides effective structural adaptability of the combined coating under friction due to relaxation of internal stresses: softening of the coating in 1.25 times, compared to BK8 coating, reduces the likelihood of local stress concentrators by increasing the integrity of the coating. The integrity of the combined coating BK8+Cu increases in 2 times, compared with the BK8 coating, due to filling the imperfections of the BK8 hard coating with copper, which contributes to the localization of normal and tangential stresses in the soft component of the combined coating.