Effect of Heat-Treatment on the Thermal and Mechanical Stability of Ni/Al2O3 Nanocrystalline Coatings

Abstract

Heat-treatment is a frequently used technique for modifying the physical and chemical properties of materials. In this study, the effect of heat-treatment on the mechanical properties, thermal stability and surface morphology of two types of electrodeposited coatings (pure-Ni and Ni/Al2O3) were investigated. The XRD analyses showed that the crystal structure of the as-deposited coating changes from slightly amorphous to crystalline as the heat-treatment temperature increases. The heat-treatment of both the pure-Ni and the Ni/Al2O3 coating caused an increase of the grain size within the coatings. However, the unreinforced Ni coating experienced a faster growth rate than the Ni/Al2O3 coating, which resulted in a larger average grain size. The temperature-driven changes to the microstructure of the coatings caused a reduction in the hardness and wear resistance of the coatings. The presence of nanoparticles within the Ni/Al2O3 coating can successfully extend the operational temperature range of the coating to 473 K by pinning grain boundaries.

Microstructural response and wear behaviour of Ti-6Al-4V impregnated with Ni/Al2O3 + TiO2 nanostructured coating using an electric arc

“…Modification of the surface of the titanium alloy. Each polished sample was coated with Ni coating deposited from a modified Watts Nickle bath solution 16,17 . The electrodeposition process was carried out in a 250 ml glass beaker.…”

“…Various particle sizes are visible in the SEM micrograph within the particle clusters. Previous studies on these materials suggested particle agglomeration occurred in the as-received powders 17,20 .…”