Electric-spark alloying of steel with hetrophase materials based on ZrN and Al2O3

Abstract

A study was made of the ESA of steel with electrodes made of ZrN-AlaO3 composites with and without MO and W additions. Al2O3 contents in excess of 10 vol. % adversely affect the conditions of formation of a strengthened layer and increase the amount of brittle rupture erosion products by decreasing the thermal fatigue resistance of the electrode material. In ESA with composites sintered in argon the coefficient of transfer is 1.5–2 times higher and the total weight gain three times greater than in alloying with composites sintered in nitrogen. The ESA of steel with a Mo-containing ZrN-Al2O3 composite results in the formation of a strengthened layer which is more continuous and adheres more closely and more strongly to the basis material than a strengthened layer produced by ESA with a composite containing the same amount of W. ESA is accompanied by a redistribution of carbon in the surface layers of the cathode, resulting in the attainment of a maximum carbon concentration in the white layer, as well as by a comminution of the ferrite grain and a change in its shape.