Please cite this article in press as: L. Thakur, et al., An investigation on erosion behavior of HVOF sprayed WC–CoCr coatings. Appl. Surf. Sci. (2011), doi:10.1016/j.apsusc.2011.09.079 ARTICLE IN PRESS G Model APSUSC-22462; No. of Pages 10 Applied Surface Science xxx (2011) xxx–xxx Contents lists available at SciVerse ScienceDirect Applied Surface Science j our nal ho me p age: www.elsevier.com/loc ate/apsusc An investigation on erosion behavior of HVOF sprayed WC–CoCr coatings Lalit Thakur a , N. Arora a,∗ , R. Jayaganthan b , R. Sood c a Mechanical and Industrial Engineering Department, Indian Institute of Technology Roorkee, Roorkee 247667, India b Department of Metallurgical and Materials Engineering, Indian Institute of Technology Roorkee, Roorkee 247667, India c M/s. Industrial Processors and Metallizers Pvt. Ltd. (IPM), Delhi 110099, India a r t i c l e i n f o Article history: Received 11 April 2011 Received in revised form 14 September 2011 Accepted 17 September 2011 Available online xxx Keywords: WC–CoCr HVOF Cermet Slurry erosion Nanostructured a b s t r a c t Present work is an investigation of slurry erosion behavior of WC–CoCr cermet coatings deposited with two different WC grain sizes. HVOF thermal spray process was employed due to its high velocity and low flame temperature characteristics resulting in quality coating. HVOF spraying was assisted with in-flight particle temperature and velocity measurement system to control its heating. Slurry erosion testing was performed using a pot-type slurry erosion tester to evaluate slurry erosion resistance of the coatings. Two parameters were considered for testing viz. erodent particle size and slurry concentration. Surface morphology was examined using SEM images and phase identification was done by XRD. The erosion behavior and mechanism of material removal was studied and discussed based on microstructural examination. It was observed that WC–CoCr cermet coating deposited with fine grain WC exhibits higher slurry erosion resistance under all testing conditions as compared to conventional cermet coating. © 2011 Elsevier B.V. All rights reserved. 1. Introduction The most common and unavoidable problem of mechanical components of automobiles, power generation units construction equipments, aircraft engine, chemical processing equipments is wear. It not only affects the life of a component but also reduces its performance. To overcome this problem, wear resistant alloys or suitable wear resistant coatings deposited by thermal spray tech- nique are generally used. Now-a-days thermal spray coatings are gaining popularity due to exceptional wear resistance property, weight reduction and cost effectiveness [1]. For industrial appli- cations, WC based cermet coatings are widely used for surface modification to enhance the wear resistance of mechanical com- ponents. WC–Co coating is most suitable for room temperature wear con- ditions. It is mainly deposited either by air plasma spraying (APS) or high velocity oxy fuel (HVOF) spraying. HVOF spraying is well proven method for the deposition of WC–Co cermet coatings due to its exceptional characteristics such as higher velocities and lower flame temperature that results in less decomposition of WC dur- ing spraying [2]. It has been observed that the wear resistance of WC–Co cermet increases significantly by reducing the size of carbide grains to the nanometers in the ductile cobalt matrix [3]. In case of nanostructured coatings, significant fraction of atoms ∗ Corresponding author. Tel.: +91 9412307242/1332 285685. E-mail address: arorafme@iitr.ernet.in (N. Arora). resides at grain boundaries, which contribute for the high hard- ness and toughness [4], so these coatings can be a better option than conventional coatings for tribological applications in the near future. But there are some problems associated with these nanos- tructured coatings such as higher decomposition of WC phase due to higher surface area to volume ratio of carbide grains in starting powder that results in decreased performance [2]. Although WC–Co coatings are successful in most of the wear conditions, but not suited for corrosive environment as compared to WC–CoCr coatings [5]. Some studies on cyclic impact, abrasive wear and sliding wear of WC–CoCr have been reported in the lit- erature [5,6]. Slurry erosion resistance of WC–10Co–4Cr AC–HVAF sprayed coated samples has improved by the addition of 15% nano WC–12Co powder into the coatings [7]. However, the studies on slurry erosion of nanostructured WC–CoCr coatings are scarce in the literature. Mostly there are two types of testing systems for calculating the slurry erosion resistance of materials. These are jet impingement system and slurry pot system; both have their own advantages and limitations. In slurry pot system, test specimens are clamped in a fixture and rotated at constant speed within a pot-type appara- tus filled with slurry medium. The slurry is composed of standard concentration and erodent particle size. The rotation of specimens within the slurry medium produces a relative motion between slurry system and specimens and impact caused by erodent particle causes the erosion of test specimens [8,9]. In pot-type slurry erosion testing, it is very difficult to control the flow conditions and certain important parameters like particle 0169-4332/$ – see front matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.apsusc.2011.09.079