Effect of constricted arc welding on tensile properties of thin sheets of aero engine grade titanium alloy

Abstract

Titanium and its alloys have been considered as one of the best engineering materials for aero-engine applications, because they possess many good characteristics such as high specific strength, superior corrosion resistance and good high temperature strength. Gas tungsten arc welding (GTAW) welding process is generally preferred because to repair aero-engine blades of its high versatility and easy applicability. Gas Tungsten Constricted Arc welding (GTCAW) is a new variant of GTAW process. It generates very high frequency (20 kHz) and alters the magnetic field of the arc, thus enabling the control of constriction of arc and leading to less heat input, narrow heat affected zone (HAZ), reduced residual stresses and distortion compared to conventional GTAW process. This paper reports the tensile properties of GTA and GTCA welded thin sheets (1.2 mm) of Ti-6Al-4V alloy used in aero-engine applications. The joints were characterized using optical microscopy, scanning electron microscopy and microhardness survey. From this investigation, it is found that GTCAW joints exhibited superior tensile properties compared to GTAW joints due to reduction of prior beta grain boundary, higher fusion zone hardness and narrow heat affected zone. Hence, it is preferred that GTCAW process can be employed to repair aero-engine components over GTAW process.