Experimental Investigations on Directed Energy Deposition Based Repair of Stainless Steel 316L Alloy Substrate Manufactured through Hot Rolled Steel and Powder Bed Fusion Process

The present study investigates the repaired components of mechanical, microstructural, and grain structures developed in initial layers of stainless steel 316L samples manufactured by directed energy deposition. The microstructural changes happening in the interface region owing to the substrate variation are studied by considering two different substrates, namely powder bed fusion substrate and hot rolled steel substrate. The novelty of this study is to make the repair work by additive manufacturing (directed energy deposition) process, which has to build the structure with different substrates (powder bed fusion and hot-rolled steel). The purpose of this study is to investigate the significance of the beginning layers of the directed energy deposition process. Alternative welding concepts for repair work applications the directed energy deposition process is used to rework or re-join a broken component's metal. Different regions of the directed energy deposition deposited samples are studied through an optical microscope, field emission scanning electron microscope, and electron backscatter diffraction analysis. The very fine crystal grains are found just above the interface region on the powder bed fusion substrate depending on the high cooling rate. The microhardness on the initial layers is based on the substrate cooling rate. Furthermore, microhardness values of 230.7 HV for PBF substrates and 225.2 HV for hot rolled steel substrates have been obtained. Tensile test results show that the TE of PBF-DED is 7% higher than that of HRS-DED samples. The YS value of 74 MPa is also higher. The UTS of PBF-DED was obtained at 582 MPa, while the HRS-DED sample reached 529 MPa. The results of PBF-DED are 53 MPa higher than that of HRS-DED.