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Role of plasma gas flow rate on the microstructural and mechanical aspects of plasma arc welded titanium alloy joints


Affiliations
1 Centre for Materials Joining & Research (CEMAJOR), Annamalai University, Annamalai Nagar, Tamil Nadu, India, India
2 Centre for Materials Joining & Research (CEMAJOR), Annamalai University, Annamalai Nagar, Tamil Nadu, India., India
     

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In the present investigation, the effect and role of plasma gas flow rate on the formation of microstructure during plasma arc welding of Ti6Al4V titanium alloy were studied using microscopic observation, energy dispersive spectroscopic analysis, tensile tests and microhardness measurements. Plasma gas flow rate influences the arc pressure, arc constriction, and stability. The transformation of plasma arc from conduction mode to keyhole mode causes severe changes to the microstructural characteristics of the titanium welds. This transformation takes place with slight variations of PGFR. Weld geometries increase with an increase in the PGFR. The microstructural examination shows that there are various phases formed during the variation in PGFR. Fusion zone had acicular α and widmanstätten α. Mechanical properties (i.e) strength and hardness of the joints increase with an increase in plasma gas flow rate. In the joint welded with 1 L/min, there is the formation of α-case which is an oxygen rich brittle subsurface structure and found detrimental to the ductility of the joints.

Keywords

Plasma Arc Welding, Titanium Alloy, Microstructure, Defects, Tensile, Hardness.
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  • Role of plasma gas flow rate on the microstructural and mechanical aspects of plasma arc welded titanium alloy joints

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Authors

T. Pragatheswaran
Centre for Materials Joining & Research (CEMAJOR), Annamalai University, Annamalai Nagar, Tamil Nadu, India, India
S. Rajakumar
Centre for Materials Joining & Research (CEMAJOR), Annamalai University, Annamalai Nagar, Tamil Nadu, India., India
V. Balasubramanian
Centre for Materials Joining & Research (CEMAJOR), Annamalai University, Annamalai Nagar, Tamil Nadu, India, India

Abstract


In the present investigation, the effect and role of plasma gas flow rate on the formation of microstructure during plasma arc welding of Ti6Al4V titanium alloy were studied using microscopic observation, energy dispersive spectroscopic analysis, tensile tests and microhardness measurements. Plasma gas flow rate influences the arc pressure, arc constriction, and stability. The transformation of plasma arc from conduction mode to keyhole mode causes severe changes to the microstructural characteristics of the titanium welds. This transformation takes place with slight variations of PGFR. Weld geometries increase with an increase in the PGFR. The microstructural examination shows that there are various phases formed during the variation in PGFR. Fusion zone had acicular α and widmanstätten α. Mechanical properties (i.e) strength and hardness of the joints increase with an increase in plasma gas flow rate. In the joint welded with 1 L/min, there is the formation of α-case which is an oxygen rich brittle subsurface structure and found detrimental to the ductility of the joints.

Keywords


Plasma Arc Welding, Titanium Alloy, Microstructure, Defects, Tensile, Hardness.

References