Energy Parameters of an Electron Beam and Structure and Mechanical Properties of Composite Coatings

Abstract

An important parameter of non-vacuum electron-beam cladding is the surface density of the input energy that depends on the beam current and the specimen travel speed. The paper presents results of investigation of the effect of the heat input on the structure and properties of composite coatings fabricated by electron beam cladding. The modes of cladding with beam currents of 25 and 40 mA and specimen travel speed varying within 0.5–2.0 cm/s have been studied. It was revealed that the thickness, the dendrite grain size, and the microhardness of the coatings increased, and the volume fraction of the eutectic decreased with increasing specific electron beam power. It is shown that for a low heat input, an austenitic-martensitic structure is formed with carbides in the eutectic and martensite needles. For a large heat input, an austenitic structure with eutectic carbide network is formed. The martensitic structure is formed only along the coating-substrate interface as a result of intense heat removal deep into the substrate material.