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V. Vaithiyanathan ¹, V. Balasubramanian ¹, S. Malarvizhi ¹, Vijay Petley ², Shweta Verma ²

Affiliations
1 Centre for Materials Joining & Research (CEMAJOR), Dept. of Mfg. Engg., Annamalai University, Annamalai Nagar, Tamilnadu, IN
2 Materials Group (MTG) Gas Turbine Research Establishment (GTRE), Bengaluru, IN

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.

Keywords

Titanium Alloy, Gas Tungsten Arc Welding, Gas Tungsten Constricted Arc Welding, Tensile Properties, Microstructure.

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P. Hariprasath ¹, P. Sivaraj ², V. Balasubramanian ³, Vijay Petley ⁴, Shweta Verma ⁵

Affiliations
1 Research Scholar, Centre for Materials Joining and Research (CEMAJOR), Department of Manufacturing Engineering, Annamalai University Annamalai Nagar - 608002, Tamil Nadu, IN
2 Associate Professor, Centre for Materials Joining and Research (CEMAJOR), Department of Manufacturing Engineering, Annamalai University Annamalai Nagar - 608002, Tamil Nadu, IN
3 Professor and Head, Centre for Materials Joining and Research (CEMAJOR), Department of Manufacturing Engineering, Annamalai University Annamalai Nagar - 608002, Tamil Nadu, IN
4 Scientist F, Materials Group, Gas Turbine Research Establishment (GTRE) DRDO, Bengaluru, IN
5 Scientist D, Materials Group, Gas Turbine Research Establishment (GTRE) DRDO, Bengaluru, IN

Abstract

Ti-6Al-4V alloy is a unique material for structural applications of aerospace industry for the excellent strength and lightweight. The fusion welding of this Titanium alloy resulted severe residual stress formation and coarser grains in the fusion zone. To overcome these problems, a solid state linear friction welding (LFW) is a emerge technique to joining of blade and disk assembly in the next generation aero engines. The plastic deformation followed by forging action resulted finer grain structures in welded regions. This investigation elaborated mechanical behavior and microstructural characteristics of linear friction welded joints. The welding parameters established by statistical response surface methodology. The fabricated joints yielded maximum tensile strength and joint efficiency of 1011 MPa and 98%. The lower microhardness recorded in the thermo mechanical affected zone (TMAZ) among the weld cross section. The weld nugget microstructure composed of equiaxed grain structure. The fracture surface revealed that joints failed under ductile mode. The result concluded that the weld failure mainly due to grain coarsening subsequent deformation leads to weld failure in the LFW joint.

Keywords

Linear Friction Welding, Titanium Alloy, Microhardness, Microstructures, Fractography.

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