Parametric investigation and characterization on SS316 built by laser-assisted directed energy deposition

Abstract

In the present work, parametric investigation and characterization of stainless steel 316 (SS316) built by laser-assisted directed energy deposition (L-DED) is performed. Single-track L-DED experiments are carried by varying laser power, scanning speed, and powder feed rate using full factorial experimental design. The effect of L-DED process parameters on the track geometry, deposition rate, and microhardness is investigated, and three different combinations of process parameters yielding maximum deposition rate and hardness are identified for bulk investigation. The identified process parameters are laser power of 1000 W, powder feed rate of 8 g/min, and scanning speed of 0.4 m/min, 0.5 m/min, and 0.6 m/min. The austenitic phase [Formula: see text] is detected at all the conditions. However, ferrite [Formula: see text] peak is observed at 0.6 m/min due to microsegregation and thermal gradients. The minimum crystallite size is estimated to be 24.88 nm at 0.6 m/min. The porosity and microstructure analysis is carried out by optical microscopic images. The fine columnar dendritic structure is observed in L-DED samples at all conditions. An average microhardness of 317.4 HV0.98 N is obtained at 0.4 m/min, and it is observed that microhardness reduces with an increase in scanning speed mainly due to increase in lack of fusion and porosity. Tribology studies are carried out at different values of normal load and sliding velocity. The minimum specific wear rate of 0.02497 × 10−4 mm3/Nm is observed at scanning speed of 0.4 m/min. Scanning electron microscope of the wear tracks analysis shows abrasive wear as the major wear mechanism. This study provides a path for building SS316 components for various engineering applications.