Metallurgical characterizations and mechanical properties on friction welding of Incoloy 800H joints
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S. Arun Kumar Department of Production Engineering, National Institute of Technology, Tiruchirappalli, Tamilnadu, 620015, India
K. Tamilmannan School of Engineering and Technology, Indira Gandhi National Open University, New Delhi, 110068, India
P. Sathiyaa) Department of Production Engineering, National Institute of Technology, Tiruchirappalli, Tamilnadu, 620015, India
B. Arivazhagan Materials Technology Division, Indira Gandhi Centre for Atomic Research, Kalpakkam, Chennai, Tamilnadu, 603102, India (Received 22 December 2015; accepted 4 April 2016)
The present work discusses about the mechanical and metallurgical properties of Incoloy 800 H friction welded joints. The process parameters namely friction pressure, friction time, upsetting pressure, upset time, and rotational speeds were varied from low level to high level to study their effects on the properties of the weldments. The tensile tests were carried out at four different temperatures namely at room temperature, 550, 650, and 750 °C. From the results, it is observed that as the testing temperature increased, there was a reduction in tensile strength of welds. The friction welds had higher hardness than the base metals. This was due to the formation of secondary phases (c9 and M23C6) in friction welds. The tensile and impact fracture surfaces were further analyzed through SEM and finally the individual effects of the parameters with respect to the microstructures variation in the welds were studied.
I. INTRODUCTION
Friction welding is a solid state joining process which is the most economical and also a feasible method in joining similar and dissimilar metals.1 It is used extensively due to its advantages such as low heat input, production efficiency, ease in manufacture, and environment cleanliness. Incoloy alloy 800H is an austenitic iron–nickel-based super alloy that has good strength and corrosion properties at high temperatures.2 The Incoloy 800H has resistance to high temperature corrosion and it is used for many applications involving long-term exposure to elevated temperatures in corrosive atmospheres. Other applications of Incoloy 800H are in super heater tubes in power generation units, and in high temperature heat exchanger tubes in gas-cooled nuclear reactors.3 The Incoloy 800H derives its strength mainly from gamma prime (c), an intermetallic compound that
Contributing Editor: Jürgen Eckert a) Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/jmr.2016.161 J. Mater. Res., 2016
enhances the strength found in other kinds of iron– nickel-base alloys with the chemical formula Ni3 (Al, Ti). Precipitation of c9 contributes to high temperature strength and creep resistance of the material, with the strength increasing as c9 volume fraction increases. The volume fraction of c9 in iron–nickel-base alloys is usually less than 25%.4,5 The composition of Incoloy 800H is very similar to that of alloy 800 with the difference that the carbon content of Incoloy 800H is more restrictive (0.05–0.10%) than the alloy 800 (0–0.
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