ORIGINAL ARTICLE Comparative study of the slurry erosion behavior of laser cladded Ni-WC coating modified by nanocrystalline WC and La 2 O 3 Parisa Farahmand & Thomas Frosell & Molly McGregor & Radovan Kovacevic Received: 2 September 2014 /Accepted: 20 February 2015 # Springer-Verlag London 2015 Abstract The erosion performance of laser cladded Ni- 60 %WC coatings subjected to a controllable abrasive water jet (AWJ) was investigated. The erosion resistance of Ni-60 %WC coatings at varied linear laser energy (from 315 to 700 J/mm) was examined under different impinging angles of a slurry jet. The chemical composition of coatings was modified by nanocrystal- line WC powder and the rare earth element (La 2 O 3 ). The erosion value of Ni-60 %WC was reduced to 40 % by decreasing the laser energy from 700 to 315 J/mm. Synthesized coatings with optimal weight fraction of nano-WC particles (5 %) and La 2 O 3 (1 %) decreased the average microstructural grain size of the Ni- binder, increased the homogeneity and hardness of the coating, and consequently increased the erosion resistivity. The tribolog- ical evaluation of the erosion scars showed a log-linear relation- ship between coating hardness and volume loss under erosion. Adding nano-WC (5 %) and La 2 O 3 (1 %) enhanced the bonding strength between Ni and WC and no pulled out WC particles was observed after erosion test. Keywords Ni-WC composite coating . Slurry erosion . Nanocrystalline WC . Rare earth element 1 Introduction Slurry erosion generally describes the metal surface degrada- tion by micro-mechanical deformation/fracture resulting from random impacts of the high velocity liquid with a solid particle suspension. Wear and erosion under slurry erosion conditions such as unprocessed oil, gas, and water mixture are the prima- ry reasons for component damage in the oil and gas industry [1]. During erosion, abrasive particles impose high-strain-rate deformation on the material. The strain rate is in the order of 10 3 to 10 6 /s [2]. Continuous impact of slurry particles induces stress in the metal surface, and by exceeding the yield stress, the plastic deformation occurs in or close to the impact region. Additionally, the yield stress of the material coating increases due to strain hardening, and eventually the yield stress be- comes equal to the fracture stress. Once this occurs, no further plastic deformation can follow. The material becomes brittle and tends to fragment from subsequent impacts [3]. The components exposed to the slurry-erosion condition require a coating with outstanding material properties. From a surface engineering perspective, hard-facing overlays such as metal matric composites (MMC) offer some unique coating characteristics to protect equipment subjected to erosion. The main beneficial property of the MMC coatings is the combi- nation of a ductile matrix with brittle hard-phase reinforce- ment. Under the slurry erosion condition, the material removal of MMC coating mainly occurs by binder surface scratching where the scratch width defines the scale of the damage. In such condition, the carbide particles resist the scratch devel- opment and deflect the erodent particles, acting as matrix pro- tector [3]. The level of the MMC coating erosion resistance is determined by the combination of erosion conditions and ma- terial properties. Microstructural integrity, microhardness, coating composition, carbide grain size, and bonding strength between constituents are the main coating characteristics in the assessment of erosion resistivity [4, 5]. It was shown that there is a log-linear relationship between hardness and volume loss under slurry erosion condition [6]. The erosion rate is also dependent on the major testing factors including test condi- tions, impact velocity, impinging particle size and shape, erodent type, and impact angle [5]. P. Farahmand : R. Kovacevic (*) Center for Laser-aided Manufacturing, Lyle School of Engineering, Southern Methodist University, 3101 Dyer Street, Dallas, TX 75205, USA e-mail: kovacevi@lyle.smu.edu T. Frosell : M. McGregor Halliburton, 2601 E. Belt Line Road, Carrollton, TX 75006, USA Int J Adv Manuf Technol DOI 10.1007/s00170-015-6936-2