Study of microstructure & mechanical properties of TIG welded aluminized 9Cr-1Mo steel

Abstract

Aluminide coating on 9Cr steel is candidate coating for blanket module applications of fusion reactors. The welding fabrication processes associated with coated steels are still an issue as the presence of Al in weld metal has several detrimental outcomes. To address this, the authors have attempted a study on conventional TIG welding with V-groove to mitigate the effect of coating on weld metallurgy. This work emphasizes the comparison of mechanical properties and microstructures of aluminide coated and uncoated/bare 9Cr-1Mo steel. Microstructural observations indicated presence of un-dissolved alumina inclusions at the weld fusion line. Despite such inclusions, the observed tensile strength of the weld joint for coated steel is 648 MPa±16 MPa which is in line with the weld joint of un-coated steel (667±14 MPa) and substrate (643 MPa±18 MPa). Impact toughness tests carried out at 0 °C,-25 °C and room temperature also indicate that there is no drastic effect of coating on weld joint and the observed toughness values are acceptable as per the reported data (45 J).