Micro Electron Beam Welding of the hybrid material combination Nitinol and stainless steel without filler material

Nitinol, which consists of 50 at.-% nickel and 50 at.-% titanium, and stainless steels. These materials are widely used in medical engineering. Due to the versatile properties of Nitinol, for example shape memory and superelasticity, it finds application in implants and medical instruments. Because of its high-cost and poor machinability, there is a high demand for dissimilar welding of Nitinol components to stainless steel. During welding of titanium-containing alloys, like Nitinol, to ferrous metals like stainless steel, intermetallic phases between titanium and iron are formed. These phases are very brittle and lead to cracks and reduced mechanical properties of the joint. This publication intends to demonstrate the feasibility of producing weld seams with good quality by the use of Micro Electron Beam Welding. Due to a very accurate beam alignment and fast beam deflection, the composition and the level of dilution in the weld metal can be precisely controlled, resulting in a significantly reduced amount of intermetallic phases. Another aim of this paper is to show that the electron-optical monitoring can be used for quality assurance.