Nickel-Titanium Alloys Welding of Thin Sheets Using GTAW: Comparative Study Between Similar and Dissimilar Welding with AISI 304 Stainless Steel

• Published in: Materials research (São Carlos, São Paulo, Brazil) Vol. 22; no. 1; p. 1
• Main Authors: Oliveira, Matheus José Cunha de, Melo, Raphael Henrique Falcão de, Maciel, Theóphilo Moura, Araújo, Carlos José de
• Format: Journal Article
• Language: English
• Published: Sao Carlos Universidade Federal do Sao Carlos, Departamento de Engenharia de Materiais 01-01-2019; ABM, ABC, ABPol; Associação Brasileira de Metalurgia e Materiais (ABM); Associação Brasileira de Cerâmica (ABC); Associação Brasileira de Polímeros (ABPol)
• Subjects: Austenitic stainless steels; Comparative studies; Diamond pyramid hardness; dissimilar joints; Dissimilar material joining; Ductile fracture; ENGINEERING, CHEMICAL; Fracture surfaces; Gas tungsten arc welding; GTAW; Heat treatment; Intermetallic compounds; Laser beam welding; MATERIALS SCIENCE, MULTIDISCIPLINARY; Mechanical properties; Metallurgical analysis; METALLURGY & METALLURGICAL ENGINEERING; Nickel base alloys; Nickel titanides; NiTi; Plastic deformation; Sheets; similar joints; Stainless steel; Tensile tests; Thermal stress; Titanium alloys; Weld metal; Welded joints; Welding; similar joints; dissimilar joints; GTAW; Welding; NiTi
• ISSN: 1516-1439; 1980-5373; 1980-5373
• DOI: 10.1590/1980-5373-mr-2018-0434

The objective of the present work was to evaluate welding of thin sheets (thickness < 1 mm) of similar and dissimilar NiTi alloys with AISI 304 stainless steel using the Gas Tungsten Arc Welding (GTAW) process and to study the mechanical and metallurgical properties of the joints with and without post-welding heat treatment (PWHT). The GTAW process was chosen because it is more economical than the usual welding processes for NiTi alloys, such as the Laser Beam Welding (LBW). The welded joints were characterized by the techniques of SEM, OM, electrical resistance in temperature (ERT), tensile test and Vickers microhardness. It was observed that the dissimilar joints presented a brittle behavior due to the formation of brittle elements along the weld metal by the excessive increase of the hardness in this region with peaks of hardness higher than 900HV. Similar joints presented superior mechanical behavior, with extensive plastic deformation before rupture and fracture surface with ductile appearance. The PWHT in the similar joints promoted a decrease in the rigidity of the material by minimizing the thermal stresses from the welding process, the PWHT did not influence the dissimilar joints mechanical behavior.