An Insight into Chip and Surface Texture Shaping Under Finish Turning of Powder Steels Infiltrated with Tin Bronze

The manufacturing of work parts made of powder (sintered) steels is currently widespread in industry, as it provides minimal processing allowances and high dimensional accuracy, as well as the required properties and unconventional chemical composition. At the same time, their low tensile or bending strength must be considered a serious disadvantage. In order to minimize these disadvantages, a number of strengthening technologies are used, among which is the infiltration of porous base materials with metal alloys. In this study, the details of finish turning of sintered iron-graphite-based steel infiltrated with tin bronze with molybdenum disulfide addition are considered. Changes in the shape of chips and their geometric features, as well as the 3D parameters and topography features of the surface machined, are presented after finish turning with AH8015 carbide inserts. The cutting speed (<i>v_c</i>) and feed rate (<i>f</i>) were used as variable parameters. It was found that when turning the powder steels under study, the chips took the shape of small fragments or element chips, including segmented chips. For quenching steel, the formation of irregular lamellae was observed and for the initial state, a serrated chip was registered. For the initial state, a reduction in <i>K_b</i> values was observed in the range of the <i>v_c</i> of 50-100 m/min and <i>f</i> of 0.05-0.075 mm/rev, and for quenching in the range of 225-250 m/min and 0.05-0.075 mm/rev. Compared to the initial state, for quenching, depending on the cutting parameters, a 14% reduction in the chip spreading ratio <i>K_b</i> or an increase from 2 to 32% was registered. For the initial state and quenching, a decrease in the <i>Sp</i> and <i>Sv</i> parameters was achieved in the range of the <i>v_c</i> of 200-250 m/min and <i>f</i> of 0.05-0.075 mm/rev, and there was an increase in the range of 50-150 m/min and 0.125-0.15 mm/rev. Compared to the initial state, an increase in the <i>Sz</i> parameter from 10 to 35% was observed for quenching. On the surfaces machined with <i>v_c</i> = 50 m/min and <i>f</i> = 0.05 mm/rev, waves and single significant peaks were observed. On the other hand, <i>v_c</i> = 250 m/min and <i>f</i> = 0.15 mm/rev provided classical feed tracks in the form of valleys and irregular ridges on the surfaces machined. The test results can be useful in the design and manufacturing of industrial parts made of powder steels.