Assessment of gold with titanium alloy weldability in conditions of a dental technique laboratory

Abstract

In dental practice, there is necessary to weld gold with titanium under the conditions of a dental technique laboratory, which is difficult. The aim was to assess the weldability of pure gold with the titanium alloy Ti6Al4V using a prosthetic laser welding machine.Gold wire in a diameter of 0.4 mm made with the use of a jewellery drawbar (GOLDPORT, Szczecin, Poland) was welded to a titanium alloy Ti6Al4V substrate of dental implant abutment screw (MegaGen). Dental laser welding parameters (Bego Laser Star T plus) were 230 V; 6.5 ms; 2.5 Hz; laser spot 0.3 mm, and argon blow. Samples were included in resin, ground (500-4000 SiC), polished (Al2O3 suspension) and etched (Kroll solution) per 20 s before observation under a light microscope.There were well-welded and poorly joined zones. The discontinuities and voids there were not visible or sparse next to the initial weld point. Dendritic structure at well-welded remelting zones and two-phase microstructure of titanium and Ti3Au phase were found. The heat-affected zone was about of 20 microns.Light microscopy was used, and precise phase identification required further investigations. Weld strength assessment requires further micro-hardness and load-bearing ability tests. Weldability concerns the model system with pure gold.In the case of elements with dimensions below 0.4 mm, the use of a laser with a smaller spot should be considered for better control of the remelting zone and mechanical positioning of the elements in order to stabilize and avoid discontinuities and voids.Prosthetic laser welding with a laser spot about of 0.3 mm allows to obtain well-welded parts of 0.3 mm in diameter under stable stitching conditions and higher than 0.4 mm in dimensions.