Toward a new era of plasma spray processing

The recent global trend of materials R&D is shifting from monolithic to materials system and from bulk to thin film and coating. It is thus a natural consequence that plasma spray processing, as an affordable and effective thin film and coating technology, is attracting global attention in materials engineering. Unfortunately, however, the current plasma spray technology for thin film and coating seems to not yet reach the sufficient technological level to meet the requirements from the fields where this technique was not applicable in the past. In this context, this paper will point out the disregarded but important issues involved in conventional plasma powder spraying to fit for high technologies and infer the future potential of novel plasma spray processing with the use of extended feedstock like gases, liquids, and various-sized powders. In particular, special attention will be given to recent challenges aiming at a development of a co-deposition process of droplets and vapors, namely, comprehensive plasma spraying.