Blown powder directed energy deposition on various substrate conditions

Blown powder directed energy deposition of SS316L powder is carried out on various substrate surface conditions of SS304 such as cleaned, sand blasted, milled, oily, cold galvanised and painted to study their influence on the process. High-speed imaging is used for process observation and the deposited tracks are analysed qualitatively and quantitatively using surface images, cross sectional macrographs and x-ray images. Frames from high-speed imaging reveal the removal of additional material from the substrate surface such as paint and oil. The stages involved in their removal: peeling and evaporation are presented. EDS analysis showed that no additional elements other than powder and substrate material are found in the track volume. The quantitative results for all specimens show that the surface conditions had minor influences on track width, track height, wetting angle, dilution and deposited cross sectional area. Defects such as porosity, inclusions and cracking were not observed related to the surface conditions. These findings could significantly reduce processing time by skipping the cleaning step before directed energy deposition such as laser cladding or repair in industrial applications.