Influence of Electroerosion Cutting and Ultrasonic Surface Modification on the Surface Quality of Heatproof СrNi73MoTiAlNb Nickel Alloy Components

The surface state of heatproof specimens of nickel-based СrNi73MoTiAlNb alloy after both wire electroerosion cutting (WEEC) with different applied energies and finishing high-frequency mechanical impact (HFMI) treatment by an ultrasonic tool is analysed. Using an optical interferometry and scan-ning electron microscopy, the peculiarities of the formed surface topography and roughness are investigated, and using x-ray diffraction analysis and en-ergy dispersive spectroscopy, the structure, chemical and phase compositions of the surface layers are investigated. In the case of the WEEC using brass wire, the surface microalloying is revealed that is not observed, when molyb-denum wire is used for WEEC. This effect determines the changes in mechan-ical properties or their absence, respectively. Instrumented indentation shows that the thermal exposure under WEEC and finishing HFMI modifica-tion result in the surface-layers’ hardening, while the microalloying detected under high-energy WEEC leads to a hardness decrease. As established, the HFMI surface modification provides a reduction in the surface-roughness parameters and, accordingly, reduces the probability of the stress concentra-tion on the microrelief and terminates harmful tensile residual stresses.