SPLAT HEAT TRANSFER AND CRYSTAL GROWTH UNDER THERMAL SPRAY CONDITIONS

A recent development in thermal spraying is to design the microstructure of coatings by controlling the sizes of the structural features within the coating so that they exhibit dimensions at the nanoscale. Improvements in performance can be in mechanical properties as well as functional properties. The size of these nano-structured features depend both on the form of the starting material (agglomerates of nanoparticles, liquid precursors) and the process conditions employed during production. Narrowing the crystal size distribution can be obtained from a carefully-controlled nucleation and growth process. This study presents a one-dimensional heat transfer model of splat cooling and solidification under plasma spray conditions. The model involves melt undercooling, nucleation and crystal growth kinetics. It intends to investigate the effect of the oxidation of various steel substrates, on the size and density of the nucleated grains.