Weldability of iron-based powder metal materials using pulsed plasma arc welding process

The objective of this study was to investigate the weldability of three different iron-based powder metal alloys (pure Fe, Fe–Ni and Fe–P–Ni alloys) using the keyhole pulsed plasma arc process (PAW). The work undertaken included the effect of pulsed welding parameters on the microstructure and mechanical characteristics of the welded joints. Microstructural examination results revealed that for the pure Fe and Fe–Ni alloys, the fusion-welded zone was free of porosity and cracks. However, the Fe–P–Ni powder metal alloy with a high level of phosphorus content (0.25 wt%) and 7 mm thickness specimen presented solidification cracks and tunneling failure as a result of high shrinking stress due to the higher volume of molten metal and faster cooling rates. This problem was overcome by reducing the thickness of the specimen to 4 mm. No significant differences were noted in the hardness profile of the welded specimens, which warranted a heating affected zone with no excessive hardness. Furthermore, tensile tests showed that the failures of the specimen occurred always in the base metal with tensile strength slightly superior to the value of unwelded samples. Therefore, this study indicates that iron-based powder metal alloys can be successfully joined by keyhole pulsed PAW process without filler metal.