M. T. Strobel, R. Steegmüller, A. Schuessler, ADMEDES SCHUESSLER GmbH, Pforzheim, Germany
Besides cutting, the major application of laser is joining of metals by welding. Since laser welding enables micro-joints in a magnitude of <100µm without use of filler material, it has become a commonly used technique in processing medical implants. Welding Nitinol, however, still remains challenging due to a limited ductility, embrittlement and reduced tensile strength in comparison to the base material.
In recent years, novel laser welding techniques have been developed, dealing with process parameters like pulse modulation, or discrete one pulse welding.
In this paper, fundamental investigations in terms of a comparison between different welding techniques and mechanical behavior of the welds will be presented. For sake of simplicity, standard geometries like micro-dogbones are used avoiding geometrical impacts on the consistency of the welds. Results of tensile tests will be discussed as well as micro-grain structure and -hardness analysis. Bending tests are used for illustrating the fatigue behavior of the welded joints also in comparison to unwelded samples. The welding behavior of different ingot materials will be compared taking the material’s previous history into account.
Summary: The authors present fundamental investigations on mechanical behaviour of micro-welded Nitinol joints as tensile tests, dynamic fatigue tests, micro-hardness etc. Comparisons to unwelded material are drwan as well as to different ingots and cold works.
