Impact of CC and PCTIG Welding on SMO 254 Joints Using Alloy 625 Filler

Abstract

Objectives: This investigation analyzes the microstructure, mechanical and corrosion characteristics of SMO 254 joints welded using constant current TIG (CCTIG) and pulse current TIG (PCTIG) with alloy 625 (ERNiCrMo-3) filler metal. Method: Optical microscopy and SEM with EDAX were employed for microstructural characterization and phase analysis. Mechanical properties were assessed through Vickers microhardness, tensile, and Charpy impact tests, followed by fracture analysis. Findings: EDAX point analysis indicates reduced Mo segregation and the absence of Nb segregation in PCTIG weldments. The overall corrosion resistance remains acceptable despite a slightly higher corrosion rate in PCTIG weldments. The study highlights the superior mechanical properties and microstructural control achieved with PCTIG welding, making it a preferable technique for SMO 254 joints. Novelty: Notably, the research establishes PCTIG as a superior method for welding SMO 254, demonstrating that it not only refines the grain structure but also significantly enhances mechanical properties, particularly toughness, by 50% compared to CCTIG. Keywords: SMO 254, SASS, Microstructural characterization, Mechanical properties, CCTIG, PCTIG