Solid/liquid erosion behavior of gas tungsten arc welded TiNi overlay

The gas tungsten arc welding (GTAW) process has been widely used in the surface damage reparation of industrial and hydraulic handling components to yield a hardfacing overlay typically composed of nickel based alloys. The pseudoelasticity of TiNi intermetallic alloy provides excellent fatigue resistance and cavitation erosion resistance. GTAW was chosen to yield a TiNi alloy overlay onto AISI 1048 medium carbon steel substrates. The microstructure of the weld overlay was characterized. Solid/liquid mixture impact tests were carried out to explore the erosion behavior of the overlay. The X-ray diffraction pattern shows that the TiNi overlay preserves the B2 phase structure as TiNi rod source material, hence the TiNi overlay exhibits pseudoelasticity and high fracture toughness. The hardness value of the overlay is increased to 8.6 GPa, far higher than the TiNi rod source material, mostly due to the trace titanium oxide formed during welding. The erosion tests show that the TiNi overlay exhibits ductile feature erosion loss with the maximum erosion loss occurring at a 30° impact angle. The work-hardening effect induced by the impact was also found on both the TiNi overlay and AISI 1048 substrate. This feature was intensified in for the TiNi overlay. The GTAW TiNi overlay can thus reduce the erosion rate of AISI 1048 substrate significantly over a wide range of solid/liquid erosion impact angles because of its higher work-hardening effect and high hardness for the as-welded structure.