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Effects of Heat Input on the Mechanical and Metallurgical Characteristics of TIG Welded Incoloy 800HT Joints

Arun Kumar S., Sathiya P.

Archives of Metallurgy and Materials

2017

Vol. 62, iss. 3

1673--1679

This study focuses on the effect of heat input on the quality characteristics of tungsten inert arc gas welded incoloy 800HT joints using inconel-82 filler wire. Butt welding was done on specimens with four different heat inputs by varying the process parameters like welding current and speed. The result indicated that higher heat input levels has led to the formation of coarser grain structure, reduced mechanical properties and sensitization issues on the weldments. The formation of titanium nitrides provided resistance to fracture and increased the tensile strength of the joints at high temperatures. Further aging was done on the welded sample at a temperature of 750°C for 500 hours and the metallographic result showed formation of carbides along the grain boundaries in a chain of discrete and globular form which increased the hardness of the material. The formation of spinel NiCr2 O4 provided oxidation resistance to the material during elevated temperature service.

Modelling and characterization of laser welded incoloy 800 HT joints

Arun Kumar S., Paulraj S.

Advances in Science and Technology. Research Journal

2016

Vol. 10, nr 30

115--126

This study aims at finding the effect of laser welding speed on incoloy 800 HT. This alloy is one of the potential materials for Generation IV nuclear plants. Laser welding has several advantages over arc welding such as low fusion zone, low heat input and concentrated heat intensity. Three different welding speeds were chosen and CO2 laser welding was performed. 2D modeling and simulation were done using ANSYS 15 to find out the temperature distribution at different welding speeds and it was found that an increase in the welding speed decreased the temperature. Mechanical properties such as tensile strength, toughness and hardness were evaluated. The effect of welding speed on metallurgical characteristics was studied using optical microscopy (OM), Scanning Electron Microscopy (SEM) with EDS, X-Ray Diffraction (XRD) technique and fractographic analysis. From the results it was found that high welding speed (1400 mm/min) decreased the joint strength. The M23C6 and Ni3Ti carbides were formed in a discrete chain and in a globular form along the grain boundaries of the weld region which increased the strength of the grain boundaries. Fractographic evaluations of the tested specimens for welding speed (1000 and 1200) mm/min showed deep and wide dimples indicating ductile failures.