Fabrication of Porous Stainless Steel by Flame Spraying of Semimolten Particles.

In this study, porous 316L deposits were processed by flame spraying under different spray conditions aimed at controlling deposit microstructure. Scanning electron microscopy (SEM) was used to characterize the microstructure of the deposits and deposit porosity was estimated from its cross section by image analysis. Results showed that porosity of 316L deposits ranged from 20 to 55% with change in spray particle melting degrees, resulting from alteration of spray parameters. To understand the deposition mechanism, the velocity of spray particles was quantitatively measured before impact and the morphology of isolated particles deposited was characterized by SEM and three-dimensional (3D) laser microscopy to estimate the melting degree of spray particles. The relationships between melting degree, spray conditions, and deposit porosity were established. The examination showed that porous steel deposits with 3D through-deposit pore-nets were fabricated through interbonding of solid cores of semimolten spray particles. It was found that the welding of particles by the molten fraction of semimolten spray particles forms large bonding necks between deposited particles, which improved the compression strength of the porous deposits over that fabricated by other conventional processes. [ABSTRACT FROM AUTHOR]