Computational and experimental determination of parameters of laser hardening zones of cast iron

Abstract

The paper presents the results of metallographic studies and tribotechnical tests of samples of special cast iron of the "C" brand for passenger train brake pads. Regression equations for determining the depth and width of laser quenching zones were obtained using a full factorial experiment. The response surfaces of the system are constructed and the patterns of change are determined the size of the quenching zones depends on the processing modes. It is shown that the greatest influence on the depth and width of the hardening zones was exerted by the radiation power and the scanning speed of the beam. The use of transverse vibrations of the laser beam increased the productivity of the processing process. The microhardness in the zones of laser quenching from the liquid state was significantly higher than the zones of hardening from the solid state in all the studied processing modes. Tribotechnical tests were carried out according to the scheme "plane (wide side of a flat sample of special cast iron grade "C") – the annular surface of the sleeve of the counter-tile (wheel steel grade 2) with the use of semi-liquid lubricant "PUMA". The load and sliding speed varied discretely. The wear resistance of laser–hardened samples was 2.4 - 2.9 times higher than the base material, depending on the area of the hardened tracks. The friction coefficients paired with the wheel steel of the samples with laser hardening decreased slightly, which will allow the use of laser hardening for passenger train brake pads without changing their design.