Comparative analysis of FWTPET welded austenitic alloy steel samples using transition fit approach: An investigation of mechanical, morphological, and microstructural properties

Abstract

FWTPET (Friction Welding of Tube-to-tube plate using an External Tool) is the modified FSW process that has been enhanced and verified mechanical and metallurgical properties in all base metals. To assess the welding strength, samples with and without a hole on the perimeter were compared utilizing a backing block and same experimental is repeated and compared without utilizing a backing block. Maximum tensile strength is employed as the output parameter for determining the optimal combination of rotational tool speed, extrusion of tube (tube projection) and impression on tube plate (depth of cut) for achieving the desired joint strength. Under a Transition fit scenario, the experiment was conducted when heat from the tool pin was transferred to the Tube and tube plate. Taguchi's L9 Orthogonal Array technique and Analysis of Variance (ANOVA) are used as optimization approaches for finding the best joint strength (tensile strength). A microstructural study was conducted to determine the grain size in the weld zone. At the study's end, welding strength was found to be exceptionally high, at 831.8 MPa for samples with a hole (WH) and 784.35 MPa for samples without a hole and utilizing backing block (WBB) respectively. The computed tensile strength values for samples with and without a hole (WoH) were 757.2 MPa and 700.8 MPa, for the value without utilizing backing block (WoBB) respectively. Later, special characterization technique is used to evaluate the joint strength at the weld interface (WI).