Laser Welding-Soldering of Titanium Alloys with Aluminum Alloys Using Microplasma Pre-Coating

The research is aimed at improving the technology of laser welding-soldering of titanium and aluminum alloys widely used in the aerospace and automotive industries. Welding is difficult due to the formation of a brittle layer of intermetallides (TiAl3), worsening the strength of the joints. To reduce the formation of intermetallides it was proposed to use preliminary microplasma spraying of METCO 54NS-1 aluminum powder coating (fraction 0-40 μm) on titanium edges of 1 mm thickness (OT4 alloy (analog ST-A90)). The coating thickness was 50 μm. Laser welding-soldering was carried out using a CO2 laser with a power of 2-4 kW, at a speed of 16-30 m/h, a defocus value of +10...+15 mm and a flow rate of shielding gases (helium – 10 l/min, argon ‒ 14 l/min). Samples made of titanium and aluminum (AMg6 (analog АА 6061)), thickness 1.2 mm) were joined overlapping with an overlap of 6-12 mm. The results showed that microplasma coating does not provide a quality joint. Residual porosity, aluminum oxides and air gaps prevented the formation of a continuous weld, which led to non-melting and burn-through. The presence of oxides on aluminum and titanium nitrides formed by interaction with air impaired metal wetting and bonding. The results indicate the need for further improvements in technology, including reducing air gaps, improving surface preparation, and utilizing alternative joining methods such as hybrid technologies and new types of intermediate layers. This will minimize the formation of intermetallides and improve the performance of welded joints. Keywords: laser welding-soldering, aluminum, titanium, plasma spraying, intermediate layer, defects.