Investigation on Weldability Behaviour of Chromium-free Nickel Filler with Stainless Steel AISI-304
Two novel Cr-free nickel based welding wires were fabricated and used to weld austenitic grade stainless steel 304 (SS304) by Tungsten Inert Gas (TIG) welding process. Two welding wires designated as 3S (without Mn) and 4N (with 2% Mn) of % wt composition 43.499Ni, 25Fe, 10Mo, 10Cu, 10Co, 0-2 Mn, 1Ti, 0.5Al and 0.001C were fabricated and welded to SS304. Comparative studies of the joints welded by these two wires are presented. The weld joints were characterized for microstructure, mechanical and fracture properties. The microstructure of the weld interface showed presence of TiC and MoC precipitates in grains and along the grain boundaries which may be responsible for strength of the weld joints. The Unmixed zone in the joint welded by 3S wire is wider than that welded with 4N. Presence of 2% Mn in 4N wire promotes the formation of γ' (gamma prime) precipitates and hence may be responsible for better joint strength than joints welded by 3S wire. Tensile tests results showed joint strength due to 4N wire to be slightly superior (by 3.5%) to joint welded by 3S wire. However the ductility of the joint welded by 4N wire was lower by 6% compared to the joint welded by 3S wire. The hardness across the weld joints showed softer Heat Affected Zone (HAZ) and hence prone to failure during mechanical loading. The joint welded with 4N wire underwent significant amount of plastic deformation before failure. The joints welded with both the wires showed ductile mode of failure.
Koushik K,Nataraj JR,Krishna M,Karthik SB