Journal of Materials Processing Technology 231 (2016) 89–99 Contents lists available at ScienceDirect Journal of Materials Processing Technology journal homepage: www.elsevier.com/locate/jmatprotec Effect of carbide dissolution on the corrosion performance of tungsten carbide reinforced Inconel 625 wire laser coating T.E. Abioye a,c , P.K. Farayibi a,c , D.G. McCartney b , A.T. Clare a,∗ a Division of Manufacturing, Faculty of Engineering, University of Nottingham, Nottingham NG7 2RD, UK b Division of Materials, Mechanics and Structures, Faculty of Engineering, University of Nottingham, Nottingham NG7 2RD, UK c The Federal University of Technology, PMB 704, Akure, Ondo State, Nigeria a r t i c l e i n f o Article history: Received 8 May 2015 Received in revised form 15 December 2015 Accepted 23 December 2015 Available online 29 December 2015 Keyword: Laser cladding Tungsten carbide Inconel 625 wire Corrosion Dissolution Microstructure a b s t r a c t In this work, clad layers of Spherotene (a mixed tungsten carbide)/Inconel 625 wire composite suit- able for hardfacing in corrosive environments were deposited. Varying laser processing conditions were employed specifically to investigate carbide dissolution. The relative amount of Spherotene dissolution in each clad layer was analysed using a combination of methods including mass gain of clad layers, quan- titative microscopic and microchemical analysis of microstructures using scanning electron microscopy (with energy dispersive X-ray analysis) and image processing software. The electrochemical corrosion performance of two typical composite clad layers formed at low and high Spherotene dissolution lev- els and Inconel 625 wire laser clad were investigated in de-aerated 3.5 wt.% NaCl solution. The results indicate that microstructural in-homogeneity, caused by the formation of secondary phases, increases as the Spherotene dissolution increases. The Spherotene dissolution increases as the energy per unit length of clad increases. The composite clad layers demonstrate decreasing resistance to corrosion as the Spherotene dissolution increases. Through careful control of process parameters, the corrosion perfor- mance of composite clad layers can be improved by reducing the amount of tungsten carbide dissolution. © 2016 Published by Elsevier B.V. 1. Introduction Tungsten carbide/Ni-base alloy metal matrix composite (MMC) coatings are currently being utilised in extending the life span of engineering components in harsh environments (Katsich and Badisch, 2011). According to Reyes and Neville (2003), these coat- ings have, for example, found applications in crude oil exploration where cost effective protection of high value down-hole drilling tools against wear and corrosion damage is required. The most commonly used among the Ni-based alloy for this application is Inconel 625 which exhibits high toughness and excellent corrosion resistance to oxidation and corrosive attack, as established by Al- Fadhli et al. (2006). Compared to other carbides such as SiC and TiC, tungsten carbide (WC) combines favourable properties such as high hardness, low thermal expansion coefficient and good wettability with molten Ni alloys (Abioye et al., 2013). Currently, the most commonly used processing techniques for making MMC coatings for off-shore applications are thermal spray- ing and laser cladding. The characteristics and performance of ∗ Corresponding author. Fax: +44 0 115 951 3800. E-mail address: adam.clare@nottingham.ac.uk (A.T. Clare). thermally sprayed WC/Ni-base alloy MMC coatings have been investigated by several authors. Liu et al. (2007) revealed that thermally sprayed coatings are limited in very demanding envi- ronments. For example, Vespa et al. (2012), has identified the decarburization of WC during spraying to form the brittle and less wear resistant (W 2 C) phase as a drawback of thermal spraying tech- nique. Also, Guilemany et al. (1995) reported that thermal sprayed coatings (including HVOF) are characterised by pores, intercon- nected splat structures and a relatively weak (mechanical) bonding at the coating–substrate interface. Morphology and characteriza- tion of laser clad composite NiCrBSi–WC coatings has been a subject of investigation by Tobar et al. (2006). It was established that the aforementioned defects can be eliminated using laser cladding. However, tungsten carbide dissolution remains a major challenge limiting the optimal performance of the WC/Ni base alloy coatings in wear and corrosive environments. In the past, extensive work has been done on the abrasive wear performance of tungsten carbide/Ni base alloy MMC coatings. For example, Huang et al. (2004) revealed that the abrasive wear rate of WC/Ni base alloy laser clad layers increases as the amount of retained WC particle in the coating decreases. Also, Leech et al. (2012) reported that a high content of uniformly distributed tung- sten carbides in a WC–Ni based metal matrix composite has been http://dx.doi.org/10.1016/j.jmatprotec.2015.12.023 0924-0136/© 2016 Published by Elsevier B.V.