Contents lists available at ScienceDirect Journal of Manufacturing Processes journal homepage: www.elsevier.com/locate/manpro Cladding Inconel 625 on cast iron via bypass coupling micro-plasma arc welding Jiankang Huang a, *, Shien Liu a , Shurong Yu b, *, Liang An c , Xiaoquan Yu a , Ding Fan a , Fuqian Yang d, * a State Key Laboratory of Advanced Processing and Recycling of Non-ferrous Metal, Lanzhou University of Technology, Lanzhou 730050, China b School of Mechanical and Electrical Engineering, Lanzhou University of Technology, Lanzhou 730050, China c School of Bailie Mechanical Engineering, Lanzhou City University, Lanzhou 730070,China d Materials Program, Department of Chemical and Materials Engineering, University of Kentucky, Lexington, KY 40506, USA ARTICLE INFO Keywords: Bypass coupling micro-plasma arc Inconel 625 QT-400 nodular cast iron Cladding ABSTRACT There is great interest to deposit a layer of Inconel 625 nickel-base super-alloy on the surface of metallic sub- strate to increase the corrosion resistance for the services in harsh environment. In this work, we use the bypass- coupled micro-plasma arc welding to form a layer of Inconel 625 on the plate of QT-400 nodular cast iron and study the effect of the bypass current on the topology of the Inconel 625 layer. There exists spatial distribution of dendrites in the cladding layer along the direction normal to the bonding interface between the cladding layer and the plate of QT-400 nodular cast iron. The fusion zone near the interface between the cladding layer and the plate of QT-400 nodular cast iron has the largest Vickers hardness of 630 HV. 1. Introduction Inconel 625 is a nickel-chromium alloy, which possesses high strength, high corrosion resistance [1,2] and wear-resistance at high temperature [3,4]. The unique properties of Inconel 625 have made it attractive to the applications in aerospace, including engine exhaust systems, fuel and hydraulic line tubing, etc. However, the high cost of Inconel 625 has limited its use as structural materials in engineering applications. Instead, surface coating and/or cladding of Inconel 625 have been used to improve structural durability and performance of engineering structures. There are a variety of techniques available for the surface coating and/or cladding of Inconel 625, including pulsed gas tungsten arc welding [5,6], laser cladding [7,8], cold metal transfer welding [9], gas metal arc welding [10], etc. Using laser cladding, Abioye et al. [11] formed a layer (cladding beads) of Inconel 625 on 304 stainless steels, and studied the corrosion resistance of the cladding beads. Verdi et al. [12] investigated the evolution of the microstructure of the Inconel 625, which was laser-cladded on ferritic and stainless steels, at high temperatures in air, and suggested that the substrate (ferritic and stainless steels) has no observable effects on the evolution of micro- structure and indentation response of the Inconel 625 heat-treated at high temperatures. Chang et al. [13] used indentation technique to examine the local mechanical behavior of the layer of Inconel 625- Cr 3 C 2 cermet formed by laser cladding, and found that the indentation modulus and hardness of the layer of the Inconel 625-Cr 3 C 2 cermet are larger than Inconel 600. Verdi et al. [14] determined the contact modulus and indentation hardness of the laser-cladded Inconel 625 on steel by nanoindentation. Feng et al. [15] found the segregation of Mo and Nb and the formation of fine microstructure after the laser cladding of Inconel 625 and the increase of the resistance to abrasive wear of the laser-cladded Inconel 625. Fesharaki et al. [16] compared the micro- structures of the Inconel 625 coatings formed by laser cladding and TIG (tungsten inert gas) cladding, respectively, and observed that the laser cladding led to the formation of finer microstructure in the coatings. Using gas tungsten arc welding, Wang et al. [17] constructed an Inconel 625 “wall” and examined the spatial distribution of microstructure and mechanical behavior. They observed the transition for directional dendrites near the bottom layer to equiaxed microstructure near the top layer. It needs to be pointed out that the high cost and high require- ments for workpiece assembly for laser cladding have limited its ap- plications in industry. The poor weldability of QT-400 nodular cast associated with the high content of carbon makes it very difficult to use traditional arc welding techniques to clad Inconel 625 of high quality on QT-400 nodular cast iron in contrast to the arc-cladding of Inconel 625 on stainless steels. Thus, it is of practical importance to develop a https://doi.org/10.1016/j.jmapro.2020.03.058 Received 11 January 2020; Received in revised form 15 March 2020; Accepted 29 March 2020 ⁎ Corresponding authors. E-mail addresses: sr2810@163.com (J. Huang), yushur1991@163.com (S. Yu), fyang2@uky.edu (F. Yang). Journal of Manufacturing Processes 56 (2020) 106–115 1526-6125/ © 2020 The Society of Manufacturing Engineers. Published by Elsevier Ltd. All rights reserved. T