Improvement the manufacturing quality of new generation heat-resistant nickel alloy products using wire electrical discharge machining

Introduction. The paper presents the results of an experimental study on the quantitative and qualitative evaluation of the surface after wire electrical discharge machining (WEDM). The purpose of this study is an experimental investigation with qualitative and quantitative analysis of surface defects in samples made of a heat-resistant nickel alloy VV751P after WEDM. Methods of research. Samples for the study with a specific geometry were obtained by the wire electrical discharge machining method in 4 modes. The operating parameters were: workpiece height (h, mm), pulse-on time (Ton, μs), and pulse-off time (Toff, μs). The samples were studied using a Hitachi S-3400N electron microscope in backscattered electron mode at 25 kV. Surface topography after electrical discharge machining was evaluated using a laser scanning microscope (LSM) LextOLS4000. Cyclic tests were performed on a universal testing machine Biss-00-100 at a test frequency of 20 Hz in a symmetrical cycle (R = −1). Results and discussion. The defective (white) layer of samples was analyzed. It is established that during wire electrical discharge machining the thickness of defective white layer is within 10 µm, both after processing in minimum and maximum mode. The surface quality index (surface roughness Ra) was analyzed. It was found that the average value of surface roughness parameter Ra is 1.62 μm when processing samples with a height of 10 mm. When the sample height increases, the surface roughness value reaches 2.6 μm after processing in minimum mode and 3.4 μm after processing in maximum mode. It is established that with an increase in workpiece height, the number of microcracks on the surface of the product increases, which is associated with the intensification of the interaction of single pulses with the processed surface. As a result of the study, it is found that at a loading amplitude of 400 MPa, an average value of the number of cycles reaches 1.50E + 05 cycles. A decrease in the number of cycles is observed with an increase in the amplitude of the loading cycles.