Impulsive electron-beam treatment of chrome-vanadium cast iron coatings

Results of investigation of effect of impulsive electron-beam treatment and following thermal treatment on structure and hardness of hardfaced chrome-vanadium cast iron coatings are presented in present paper. The coatings were obtained by electron-beam hardfacing on low-carbon steel substrates. After grinding surfaces of the coatings were locally treated by impulsive focused electron beam with discrete point distribution in a square packing on the surface area. The research results showed that the modified zones consist of two phases. The first phase is supersaturated austenite. The second phase locally distributed in the volume of modified zone is the nucleation centers of eutectic. Results of measuring by NanoTest system showed that modified zones have low values of hardness. Low hardness values are probably caused by presence of significant volume of supersaturated austenite in modified zone. Following thermal treatment of samples led to significant increasing of hardness of modified zones. As a result of thermal treatment supersaturated austenite is decomposed on eutectoid with nanoscale structure components. Increasing of thermal treatment temperature results in decomposition of supersaturated austenite, growth and coagulation of carbide phase in the modified zones. Carbide phase is characterized by various values of dispersivity in the range from tens of nanometers up to micrometers depending on thermal treatment conditions. Carbide phase is uniformly distributed in the modified zones. Impulsive electron-beam treatment and following thermal treatment of samples with chrome-vanadium cast iron coatings allow both improving the structure and increasing the hardness of the modified zones significantly.