Microstructural and mechanical properties evolutions of plasma transferred arc deposited Norem02 hardfacing alloy at high temperature

Plasma-transferred-arc welded Norem02, an iron-based hard-facing alloy, was characterised. Its microstructure and chemical composition were investigated using optical microscopy, scanning electron microscopy (with electron probe microanalysis), electron backscattering diffraction, and X-ray diffraction. The microstructure of the as-deposit alloy consists of a dendritic austenite structure with ferrite islets at dendrites centres, with an interdendritic eutectic region containing austenite, M7C3 and M23C6 carbides and zones containing Mo-rich precipitates. Tensile behaviour of Norem02 was characterised and completed by dilatometry tests in welding process temperature range. No significant phase transformation was detectable during mechanical testing. Different heat treatment cycles of ageing at high temperatures (until 1100 °C) were carried out for different durations. The microstructure of Norem02 heated at 1100 °C was not significantly affected by a short time (15 s) treatment whereas changes were observed for longer durations (2 h), although hardness remains almost unchanged. This work tends to demonstrate that for this alloy metallurgical evolution during the welding process has very little influence on mechanical properties.