Plasma Arc Welding of NiTi and 304 Steel

Abstract

Heterogenous welds of Nitinol and austenitic stainless steel 304 were done by micro plasma welding. Both materials have wide utilization in medicine, especially NiTi is very promisive material, but with rather difficult weldability. The quality of welds was estimated by means of metallography, hardness measurement, and tensile strength test. It was found out that homogenous welding of NiTi as well as heterogenous NiTi+304 welds very much decreases mechanical properties. In homogenous weld, strength, hardness drops to 260 HV (BM 350 HV) because of grain growth. Heterogenous welds have high hardness, up to 800 HV caused by precipitation of brittle intermetalics. PAW was found not to be suitable for nitinol welding.

Mechanical Properties of NiTi Shape Memory Alloys Welded Joints: A Comparative Study between the GTAW, PAW and LBW Processes

“…Among the welded joints that were not submitted to PWHT (Fig. 3a), only the joints welded by the GTAW process showed satisfactory mechanical resistance [21,23,25], reaching about a tensile strength of 740 MPa and 13,8% strain, higher than those observed by other authors [5,7,10,11,14,20,22,24,[26][27][28][29][30]. After the PWHT, the joints welded by the PAW and LBW processes were able to withstand higher stress and strains, with the exception of welded joint L7 that was welded with a welding speed of 1500 mm/min, making the heat it impossible to fully penetrate in the weld zone besides facilitated the precipitation of brittle compounds in HAZ.…”

“…It would be possible to expect the same behavior for the NiTi SMA. However, according to several authors [7,[11][12][13][14] the GTAW and PAW welding processes negatively affects the mechanical properties of welded joints of NiTi alloys due to a large extension of HAZ. Therefore, this article aims to evaluate the mechanical and physical properties of NiTi SMA welded joints by GTAW, PAW and LBW processes through microhardness measurements, tensile tests and phase transformation temperature.…”

Effect of Mechanical Properties and Corrosion Behaviour of Martensitic Stainless Steel 410 1.6mm Butt Welded by Plasma Arc Welding

“…The plasma gas is typically Ar. Plasma arc welding process, preferably than the gas tungsten arc weld, is frequently employed for butt pieces because of its greater potential density [3], excellent arc balance, diffusion intensity, joint development, and thermic frown.…”