Influence of high current pulsed electron beam irradiation on the microstructure and mechanical properties of nanolayered-TiN/ AlSiN coatings

Nano-multilayered TiN/AlSiN coatings deposited onto cemented tungsten carbide substrates by arc ion plating have been subjected to high-current pulsed electron beam (HCPEB) treatment. The impact of pulse number on the surface morphology, phase composition and mechanical properties of the TiN/AlSiN coatings were investigated. A microstructural evolution from a superlattice structure to a composite structure was noticed using transmission electron microscopy. The surface morphology of the coatings first deteriorated due to irradiationinduced coating peeling-off and cracks, and then improved with a further increase in HCPEB pulse number, as the surface roughness value reached a maximum of 0.42 mu m after 5-pulse of HCPEB irradiation and a minimum of 0.22 mu m after 15-pulse of irradiation. An increase of HCPEB pulse number led to a gradual decrease in both hardness (H) and elastic modulus (E) of these coatings, as the values of H and E dropped from 34.0 GPa and 439.7 GPa (original TiN/AlSiN coating) to 26.2 GPa and 399.6 GPa (the coating treated with 20-pulse of irradiation), respectively. The degradation in mechanical properties was due to microstructural change and the formation of the network of cracks.