Experimental investigation on laser directed energy deposition of functionally graded layers of Ni-Cr-B-Si and SS316L

S.M. Banait, C.P. Paul, A.N. Jinoop, H. Kumar, R.S. Pawade, K.S. Bindra

Research output: Contribution to journalArticlepeer-review


Functionally Graded Material (FGM) is necessary for successful performance of two dissimilar materials joint, specifically when there is a large difference in the thermophysical properties of the materials and the joints are subjected to cyclic loading and extreme duty conditions. Laser Additive Manufacturing using Direct Energy Deposition (LAM-DED) is one of the advanced additive manufacturing processes favored for fabrication of FGMs. In the present work, an indigenously developed LAM-DED system is deployed for fabricating FGM of Ni-Cr-B-Si and SS316L. Parametric study is performed by varying the laser power, scan speed and powder feed rate and process parameter combination is identified for depositing uniform and continuous Ni-Cr-B-Si tracks with aspect ratio greater than 5. The identified process parameter combination is deployed for fabricating FGM of Ni-Cr-B-Si and SS316L and the composition of fabricated FGM is confirmed using Energy Dispersive Spectroscopy analysis. The surface topography analysis using Scanning Electron Microscopy indicates that the amount of partially melted powders increases with the increase in concentration of SS316L. Microstructure of as-built deposit is primarily dendritic with fine dendrites of ~5 µm. Micro-hardness and Single Cycle Automated ball indentation (SC-ABI) measurements indicates higher hardness and lower energy storage capacity for Ni-Cr-B-Si rich region as compared to SS316L rich region. The highest microhardness value of 645.23 HV1.96N is observed at the top layer of the graded deposit where Ni-Cr-B-Si fraction is 100%. SC-ABI testing indicates that the energy storage capacity of the material increases with increasing concentration of SS316L with similar trend for maximum displacement of the indenter. Further, LAM-DED deposits are heat-treated in muffle furnace at 900 Deg. C for two hours. The microstructural examination of thus heat-treated samples shows recrystallized grains in the Ni-Cr-B-Si rich region while dendritic microstructure is retained at the SS316L rich region. X-ray diffraction studies shows the difference in the diffraction patterns of as-built and heat-treated deposits with the absence of Ni3B phases in heat-treated samples. Microhardness studies indicate a large difference in hardness values in as-built and heat-treated deposits with a micro-hardness of 255.6 HV1.96N for 100% Ni-Cr-B-Si. SC-ABI studies show that heat treatment improves the energy absorbing capacity of the graded deposit. This study paves a way for the fabrication of Ni-Cr-B-Si and SS316L FGM with tailored mechanical and microstructural properties.
Original languageEnglish
Article number105787
JournalOptics and Laser Technology
Publication statusPublished - 31 Aug 2019


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