Microstructural, mechanical, and corrosion behaviour analysis of Monel 400 fabricated using CMT-WAAM

Abstract

Wire Arc Additive Manufacturing (WAAM) is a promising technique for fabricating large free-form components from exotic materials like stainless steel, superalloys, aviation grade aluminium alloys, etc. The majority of these alloys exhibit limitations when fabricating intricate structures using conventional manufacturing techniques. In the present work, a single-pass multi-layer wall structure of Monel 400 alloy was deposited using the CMT-WAAM technique, and the microstructural, mechanical, and corrosion behaviour was studied to assess the suitability of the deposited structure for various marine applications. The microstructure was analysed in the building direction, where finer equiaxed dendrites were observed in the bottom region, gradually transforming into coarse elongated dendrites in the top region of the deposited structure. Along with the change in microstructure, a variation in average microhardness was observed in the building direction, decreasing from 286 HV0.1 in the bottom region to 249 HV0.1 in the top region. The tensile specimens tested along the building direction fractured in the gauge length towards the top region of the wall, with an average yield strength of 353 MPa, ultimate tensile strength of 718 MPa, and percent elongation of 39 %. The electrochemical corrosion test in a 3.5 wt% NaCl solution was performed at the central region of the deposited structure. The CMT-WAAM deposited Monel 400 showed an exceptionally low corrosion rate of 0.03 mm/year. The experimental results confirmed that CMT-WAAM deposited Monel 400 exhibits mechanical and corrosion properties similar to or superior to conventional Monel 400, establishing the credential of the process for marine applications. © 2024