Quality Improvement of Wear-Resistant Coatings in Plasma Spraying Integrated with High-Energy Heating by High Frequency Currents

摘要

The paper presents the results of metallographic and energy-dispersive studies of a wear resistant coating structure made from high-chromium cast iron powder in the course of integrated plasma spraying and high-energy heating by high frequency currents (HEH HFC). The problem of determining the intensity and the nature of residual stress distribution in the depth of the hardened layer is solved by the finite element method and ANSYS and SYSWELD software systems. The results of numerical simulations were checked in field experiments using X-ray and mechanical methods for residual stress measurement. An optimum mode of fusion by high-frequency heating (the source specific power q_s = (3.0 - 3.2)·10~8 W/m~2, relative velocity of parts V_d = 60 - 80 mm/sec) was determined. In doing so compressive residual voltage (σ_(RS) ≈ -120 ± 10 MPa) was formed in the surface layer; the coating porosity reduced and the distribution uniformity of microhardness in the depth of the hardened layer improved. It was found that after plasma spraying of the surface of the part was characterized by a sufficiently developed non-uniform topography with a maximum deviation of high-altitude performance PV = 80 - 160μm and roughness Ra = 25μm ± 10μm. After thermal reflow by high-frequency heating, roughness reduced significantly (Ra = 6μm ± 2μm) and the homogeneity of the material improved (PV = 4 ... 10 μm).