| The influence of welding parameters on the plasma transferred arc welding (PTAW) process was investigated. Autogenous welds (i.e., no added material) were completed with variations in heat input, plate chemistry, and welding gases. An operating map was produced that identified operating zones and regions where fusion flaws formed. A weld bead humping phenomenon was observed and investigated; the effects of minor alloying elements and welding gas compositions are discussed. Next, an understanding of process behaviour was sought for PTA overlay welding of martensitic 410 stainless steel, with and without tungsten carbide, as the cladding material. Using argon for the plasma, carrier, and shielding gases, standard operating conditions were determined by optimizing the torch motion, arc energy, and powder delivery. Gas compositions were then varied with additions of helium, hydrogen, nitrogen and carbon dioxide. The changes in the effective heat input, oxidation/reduction behaviour and weld bead formation were recorded with video photography. |
