Surface layer modification methods using concentrated energy sources to ensure high heating rates of approximately 104 – 105 °C/s are becoming increasingly common in an attempt to improve operational performance of machine components. As a result, it is quite difficult to determine heat cycle parameters by means of experiments to predict the required intensity and distribution behavior of residual stresses and strains. The paper addresses the issue of numerical simulation of the stress-strain behavior during high energy heating by high frequency currents (HFC HEH). A finite element model has been generated using the ANSYS and SYSWELD software based on numerical computations of differential equations for transient heat conduction (Fourier equation), carbon diffusion (Fick's second law), and the elastic-plastic behavior of the material. The simulation data was verified by full-scale experiments using optical and scanning microscopy and mechanical and X-ray methods to determine residual stresses. It has been established that the level of residual compressive stresses on the component surface can be from-500 to-1000 MPa within the range of HFC HEH process variations under review. It is proven in theory and confirmed by experiments that the transition layer thickness must amount to 25 – 33 % of the hardened layer depth for the tensile stress peak to shift to deeper material layers while compressive stresses on the surface decrease by 6 – 10 %, in order to prevent hardening cracks.
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 qs= (3.0 - 3.2) ∙ 108W / m2, relative velocity of parts Vd= 60 - 80 mm / sec) was determined. In doing so compressive residual voltage (σRS≈ -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 - 160 μm and roughness Ra = 25 μm ± 10 μm. After thermal reflow by high-frequency heating, roughness reduced significantly (Ra = 6 μm ± 2 μm) and the homogeneity of the material improved (PV = 4 ... 10 μm).
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