New insight on the solidification path of an alloy 625 weld overlay

Abstract

Ni-based alloys are a special class of engineering material with excellent corrosion resistance in harsh environments. However, microstructural changes due to the solidification, may result in solidification cracks and reduction in the corrosion resistance. Knowing the microchemical and microstructural evolutions during the solidification of these alloys is essential for the understanding of the relationship between the metallurgical aspects and the properties. This research presents a new insight on the solidification path of alloy 625 weld metals deposited by the TIG cold wire process on the C–Mn steel plates. After the welding, samples having been extracted and evaluated by the scanning electron microscope, transmission electron microscopy and energy dispersive X-ray spectroscopy techniques. The results showed the presence of two types of secondary phases, identified as Laves phase and complex nitride/carbide particles. Due to the presence of nitrides particles, stable in the solid state during the melting of the alloy, during the solidification it is noted the occurrence of a complex nitride/carbide precipitation. This implies in a new route to explain the solidification of the aforementioned alloy.