Structure of the surface layer of a wear-resistant coating after treatment with a high-intensity electron beam

Abstract

Transmission electron microscopy is used to investigate the carbon extraction replicas of a wearresistant surface layer formed on Hardox 400 steel and its phase composition. The formation of a multiphase state is revealed, which includes a-iron grains and inclusions of carbide phases based on iron, chromium, and niobium. The surface layer is additionally treated by a high-intensity pulsed electron beam. The relative position of α-iron grains and particles of carbide phases is examined by the electron-diffraction microscopy of thin foils. The main carbide phase is iron carbide located as extended interlayers which separate a-iron grains. Nanoscale particles of chromium and niobium carbides are located at the interfaces of the a-iron–iron-carbide system and in the body of the a-iron grains. It is established that the surface layer is in the elastic-stress state during pulsed electron-beam treatment due to ultrahigh heating and cooling rates. It is shown that stress concentrators are the interphase boundaries between the carbide and the a-phase of iron.