Influence of deposition strategy on the microstructure and fatigue properties of laser metal deposited Ti-6Al-4V powder on Ti-6Al-4V substrate

Fatigue testing was conducted to investigate the potential of applying Laser Metal Deposition (LMD) as a repair method for Ti-6Al-4V aerospace components. Ti-6Al-4V powder was laser deposited on Ti-6Al-4V specimens with two different deposition strategies: a raster pattern with a continuous deposit (LMD-1) and a raster pattern deposit with an inter-track pause (LMD-2). The results showed fatigue lives of LMD-1 were higher when compared to LMD-2. This was mainly due to the high number of defects in LMD-2, mostly lack of fusion (LOF) defects. Despite the high number of defects, fracture surfaces for both LMD-1 and LMD-2 showed initiation to be from oxygen enriched inclusions, which could be related to contamination. This study shows the deposition strategy influences fatigue lives when laser depositing Ti-6Al-4V powder on Ti-6Al-4V substrate and there are possibilities of oxygen and nitrogen related inclusions that introduce brittle regions that are more detrimental to the fatigue performance than LOF defects or gas pores.