Warm Spraying: An improved spray process to deposit novel coatings

Warm Spray is an atmospheric coating process through continuous impact and deposition of solid particles heated and accelerated by a supersonic jet controlled between 800~1900 K and 900~1600 m s− 1. This paper introduces successful fabrication of dense and less-oxidized metallic titanium (Ti) coatings by Warm Spray and clarification of phenomena occurring upon the spray process. Temperature and velocity of an in-flight Ti particle were compared between measurement by the diagnostic instrument and calculation based on the fluid dynamics simulation. Deformation behaviour of particle from impact to deposition was analyzed through the finite element method (FEM). Densification of stacking particles was attained by applying bi-modal size distribution to the feedstock Ti powder. Qualitative restriction of changes in chemical composition of Ti coating obtained was demonstrated by elemental analysis and by calculation based on the oxidation model. Warm Spray enables various materials to fabricate coatings without thermal deterioration of the original characteristics such as purity and crystallographic phase.