The turning of overlays using sintered carbide tools

摘要

Surfacing technology is used to produce layers with special properties for new parts or for worn out functional surfaces. For many parts, it is necessary to machine them to fulfill the requirements for shape, sizes, and roughness, but the machining of overlays is, in comparison with the machining of drawn or rolled semi-products, specific. Usually, the optimization of the cutting conditions issues from the long-term tool-life test results. For these tests we have experimentally determined time dependences of tool wear at different cutting speeds for every combination of overlay and cutting material. These dependences are the basis for the determination of the relationship between tool life and cutting speed for the limit of the tool wear. The relationships between cutting speed and tool life determined in this way are the initial values for the own optimization of the cutting conditions. It is usual to determine the optimum for the minimum machining costs criterion. In the calculation, all economic indexes of the workshop are included. Measuring of the overlay hardness, HRC, and of the overlay surface roughness, R_a and R_t, after machining was also part of the tests. In this paper we publish the results of long-term tool-life tests made during the turning of an overlay made by welding on the wire C 508 using the tool from the firms Kennametal Hertel, Mircona, Sandvik Coromant, Walter and Widia. In the tests we used five types of tool material in form of inserts WNMA and WNMG type. The best results were achieved using the Kennametal Hertel WNMG 080412 KC 9315 insert. During the tests we found that the roughness of the turned surface slowly increases and that extensive deterioration occurs at the end of the tool life.