Increasing the Quality of Metal-Cutting Tools Operating under Radiation Exposure Conditions

Abstract

The paper presents the results of investigation of a new technology for increasing the resistance of metal-cutting tools (MCT) operating at nuclear power plants (NPPs) under radiation exposure conditions. The technology consists in applying the Composite Electrochemical Coating (CEC) composition of ESARb + ESA (1M + Mo + EG-4). The analysis of literary sources devoted to this subject has shown that there is a shortage of two vital ingredients of hard alloy tools for the EU industry, namely, tungsten and cobalt, which are included into the group of the fourteen (14) most important raw materials (CRM). There is also an increase in the use of the MCT made of high-speed steels with wear-resistant coatings free of CRM. The authors emphasize that when using the MCT in the NPP system, the elements, which become a source of dangerous long-lived isotopes if irradiated, should be avoided. Primarily, this concerns cobalt. Therefore, the purpose of the paper was to improve the quality of the MCT for operation under radiation exposure conditions by analyzing and synthesizing existing analogues, industry experience and recommendations in domestic and foreign literature due to application of the electrospark coatings that do not contain dangerous long-lived isotopes. Owing to the use of the proposed technology for applying the protective CECs to the MCT working surfaces, the microhardness and the continuity of the formed surface layers increase, respectively, to 12100 MPa and 100 %, and the roughness, Ra, decreases to 0.6 μm. The comparative tests have established that due to application of the CEC composition of ESARb + ESA (1M + Mo + EG-4) to the working surfaces of steel P6M5, their stability coefficient, in comparison with the non-strengthened ones, increases for the M12×1.0 taps; end mills Æ 36, and chisel cutters of S = 30 mm, respectively, by 8.0; 6.6 and 3.5 times.