Effect of NiAl and NiCr coatings on high cycle fatigue and corrosion behavior of direct metal laser sintered Ti-6Al-4V alloy

Direct Metal Laser Sintering (DMLS) of Ti-6Al-4V alloy for aviation applications shows tremendous potential due to one go fabrication with zero material waste. However, it is essential to characterize the fatigue and corrosion behavior of the 3D printed components to ensure the proper operation and safety for aviation applications. This work investigates the effect of plasma spray coatings on the high cycle fatigue and electrochemical corrosion behavior of DMLS heat-treated (HT) Ti-6Al-4V alloy. Specimens were coated with NiAl and NiCr powders as the top coat, and NiAl as the bond coat using the plasma spray technique. High cycle fatigue tests were performed, and their fractured surfaces characterized using scanning electron microscopy. Electrochemical corrosion tests were also performed and the results compared against wrought Ti-6Al-4V alloy specimens. NiAl-coated specimens showed nearly 11 % improvement in fatigue life compared to uncoated DMLS HT specimens. However, NiCr-coated specimen showed lower fatigue life. The NiAl-coated DMLS HT Ti-6Al-4V samples showed the higher corrosion resisting thermodynamic tendency than NiCr coated and wrought specimens. However, the uncoated DMLS HT specimens possess the better corrosion resistance (431.43 kΩ/cm 2 ) in comparison to NiAl-coated (61.40 kΩ/cm 2 ) and NiCr-coated DMLS HT Ti-6Al-4V specimens (33.62 kΩ/cm 2 ). All specimens showed higher corrosion resistance than the wrought Ti-6Al-4V alloy specimen (10.10 kΩ/cm 2 ). • NiAl and NiCr powders were deposited over DMLS HT Ti-6Al-4V substrates using plasma spray coating technique. • NiAl coating showed better surface finish and microhardness compared to NiCr coating. • NiAl-coated DMLS Ti-6Al-4V showed better high cycle fatigue strength and better corrosion-resisting thermodynamic tendency.