Metallurgical Approach for the Development of Heat Treatment Applied to 316L Stainless Steel Cold Spray Coatings

Abstract

Industries developing cold-spray processes aim at producing dense and resistant coatings. Controlling microstructure and inter-particular fracture characteristics of sprayed coatings is essential to improve their properties. To do so; post-spraying heat treatment is a promising approach. This work addresses the development of such heat treatments and focuses on the analysis of recovery and recrystallization. Different heat treatment parameters were explored; namely; holding temperature and time; heating rate; and heating method. This approach revealed a competition between recrystallization and other microstructural evolution mechanisms; such as precipitation and porosity coalescence. An optimized heat treatment; allowing microstructural softening and adequate mechanical properties; was sought after. First; differential scanning calorimetry measurements applied to as-sprayed coatings enabled to identify recovery and recrystallization temperature ranges. Then; a variety of heat treatments was applied; involving long-time isothermal holdings as well as shorter cycles. Microstructure analysis and hardness measurements allowed making a first selection of treatment conditions.