Tribostrain and Thermoelectric Characteristics of the Friction Process during Turning of a Hybrid Part with a Welded Seam

The tribological and thermoelectric characteristics of the turning process of a hybrid part made of 09G2S steel, the surface of which contains a weld, have been estimated using T15K6 hard alloy plates at various cutting speeds. In the used model, the rake face of the lathe cutter, which contacts chips of different composition at the stage of cutting into the weld, has been presented as two parallel heavily loaded tribosystems with variable geometric parameters of contact, which differ in tribostrain indicators and surface temperature. Based on the graphical model of the removed non-uniform allowance, its composition and geometric characteristics of fragments for each processed material have been established. Based on the obtained dimensions of the hybrid allowance elements, the maximal contact temperatures have been calculated for each tribosystem at various cutting speeds. The cutting speed that ensures a minimal difference in surface temperatures in different areas of the front face of the plates has been determined. It has been established that the turning speed, at which, according to the calculated data, more uniform heating of the front face occurs, is characterized by a decrease in fluctuations of the thermo-EMF arising at the stage of cutting the plate into the weld. Exceeding this speed leads to an increase in the negative influence of thermoelectric effects, which contribute to the intensification of wear of cutting plates. The presented research results, in combination with other technological factors for selecting processing modes, can be used to assign permissible turning speeds for welded areas on hybrid parts.