Gradient state of the surface layers of iron and nickel after electro-explosive alloying

Light microscopy, x-ray phase analysis, and scanning and transmission electron microscopy were used to study the structural-phase states of the regions created by the electro-explosive boriding of nickel and the boron carbiding of iron and nickel. Alloying of the surface of tool steel Kh12 with gadolinium and boron was also examined. It was found that several layers with distinctive features are formed, these layers being arranged in a regular pattern through the depth of the alloying zone: a near-surface nano-composite layer composed of synthesized phases; an intermediate layer characterized by cellular crystallization; a boundary layer with a granular structure; a fine nanocrystalline sublayer at the interface between the alloying zone and the base; a heat-affected zone with a high dislocation density. The properties of the surface of steel Kh12 after treatment were studied by measuring microhardness, wear resistance, and resistance to high-temperature oxidation in atmospheric air. An analysis was made of the convective processes that are responsible for mass transfer of the alloying elements in the surface layers during the treatment.