TRENGTHENED LAYER AT PLASMA HARDENING DURING WHOLE-ROLLED WHEEL

Abstract

The experiments showed the effect of hardening modes on the width of hardened tracks. With an increase in the plasma arc velocity by a factor of 4, the track width decreases by ~ 30%, and an increase in current by a factor of 2 leads to a proportional increase in the track width. The effect of the cooling rate on the characteristics of the hardened layer during plasma quenching is studied. It was shown that the cooling rates at temperatures corresponding to the austenitic region (not less than 750 0С) and the decomposition temperatures of austenite with the formation of perlite (700-500 0С) significantly exceed not only the critical quenching rate, but also the cooling rate during volume quenching in water or oil. As the temperature decreases and it reaches the martensitic transformation region, the cooling rate slows down. This helps to prevent the formation of internal quenching stresses arising from the temperature gradient. The experimental hardening of a solid-rolled railway wheel at the UDGZ-200 installation shows that in the range of practical operating modes, the surface layer of the wheel is hardened, which confirms the calculated conclusion about the optional supply of coolant (water) to the hardened surface during plasma hardening. The experimental hardening of a solid-rolled railway wheel at the UDGZ-200 unit in the range of practical operating modes provides hardening of the surface layer of the wheel, which confirms the calculated conclusion about the optional supply of coolant (water) to the hardened surface during plasma hardening.