Effect of Glass Lubricant on the Hot Extrusion of Inconel 625 Alloy
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ORIGINAL ARTICLE
Effect of Glass Lubricant on the Hot Extrusion of Inconel 625 Alloy Zhi Jia1,2
•
Xuan Sun1 • Jinjin Ji3 • Yanjiang Wang1 • Baolin Wei1 • Lidan Yu1
Received: 17 July 2020 / Accepted: 29 August 2020 Ó The Indian Institute of Metals - IIM 2020
Abstract A combination of numerical simulations and experiments was used to study the influence of glass lubricant on the hot extrusion of Inconel 625 alloy. The results showed that the glass lubricant left a large amount of abrasive debris and furrows on alloy surface, which produced different friction states. The use of a lubricant changed the alloy microstructure, decreasing the grain size, the high-angle grain boundaries (HAGBs), and the dynamic recrystallization volume fraction of the sample with lubricant. The temperature increase due to deformation and friction heat significantly affected the stress, strain, and flow rate of the billet during extrusion. The uneven friction states generated excessive local frictional heat, making the billet prone to overheating and crack initiation. The frictional heat caused local grain size and stress differences in the billet, causing further expansion of cracks. Keywords Inconel 625 alloy Hot extrusion Glass lubricant Microstructure Numerical simulation
& Zhi Jia [email protected] 1
School of Material Science and Engineering, Lanzhou University of Technology, No. 287 Langongping Road, Qilihe District, Lanzhou 730050, Gansu Province, People’s Republic of China
2
State Key Laboratory of Advanced Processing and Recycling of Nonferrous Metals, Lanzhou University of Technology, Lanzhou, Gansu Province, People’s Republic of China
3
School of Materials Engineering, Lanzhou Institute of Technology, Lanzhou, Gansu Province, People’s Republic of China
1 Introduction Inconel625 is a nickel-based alloy with Mo and Nb as the main strengthening elements [1]. It is widely used in aerospace engines, industrial gas turbines, nuclear power equipment, petrochemical, and other pipeline systems due to its good corrosion and oxidation resistance, durability, and mechanical strength when used at medium and high temperatures (600–900 °C) environment [2–5]. These nickel-based superalloys are mainly used as pipes and bars in various fields during processing and production. Hot extrusion forming is the main method for making tube blanks for high–temperature alloys. Glass lubricants have high adhesion, melting points, and compressive strength at high temperatures; therefore, glass lubricants are used to reduce the extrusion forces and mold abrasion during the hot extrusion of Ni-based superalloys [6]. The hot extrusion forming of superalloy large pipes is complex due to interactions between multiple parameters [7]. Complex dynamic recrystallization occurs during the hot deformation of superalloys, which is very sensitive to the strain rate, deformation temperature, and degree of deformation [8, 9]. Uneven lubrication during the hot extrusion greatly increases the likelihood of alloy tubes cracking or fracture, increasing the c
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