Obtaining and characterization of Ni-Ti/Ti-Mo joints welded by TIG process

• Welding Ni-Ti/Ti-Mo TIG process.
• Thermal performance evaluation of welded joint.
• Study of the effect on corrosion welded joint.
• Optimization of heat treatment conditions using response surface methodology.

The assessment of heat treatment on dissimilar Ni-Ti and Ti-Mo welding has been evaluated in this work. An experimental design 32 was used as optimization tool to evaluate the effect of time and temperature after the welding process on the welding quality. Welded joints without significant difference in the thickness of the welded wires were obtained successfully. After the heat treatment welded joints with shape memory were obtained. After the welding process a change in the chemical composition of the melting zone has been observed. There was a decrease of nickel, molybdenum and zirconium content and an increase of the titanium content. The temperature and time of heat treatment affected the corrosion resistance performance. It was observed that the short time and lower heat treatment temperature favors the formation of Ni4Ti3 precipitate, which is responsible for the formation of stable passivation film. The longer the time and temperature of heat treatment more the decrease in the corrosion resistance and increase in the fragility of the obtained joints, and consequently the amount of the precipitated Ni4Ti3.