Electroless deposition and characterization of Ni–P–WC composite alloys Z. Abdel Hamid a, ⁎ , S.A. El Badry b , A. Abdel Aal a a Central Metallurgical R & Development Institute, P.O. 87 Helwan, Cairo, Egypt b Physical Department, Faculty of Science, Al Azhar University, Nasr City, Cairo, Egypt Received 20 September 2006; accepted in revised form 1 November 2006 Available online 28 December 2006 Abstract A composite coating Ni–P–WC was produced using an electroless deposition technique from citrate bath containing WC powder. The influence of plating parameters such as WC content, pH, temperature and stirring rate on the content of WC codeposited with Ni–P alloys were investigated. The maximum value of WC (50–55 V p ) codeposited can be achieved at a particle content of 20 gL - 1 in the electrolyte, at pH 5.5–6, temperature 85–90 °C and stirring rate of 150 rpm. Surface morphology and microstructure of Ni–P–WC coatings were determined by means of SEM and X-ray diffraction. It was found that the phase structure of the solid solution cannot be varied by codeposition of WC particles in Ni–P alloys, and it only influences the growth of the crystal planes. The properties of the composite such as hardness and abrasion resistance were also examined and compared with WC free nickel deposited layer. The presence of WC particles in the deposit significantly was found to improve the hardness and abrasion resistance of composite coatings. © 2006 Elsevier B.V. All rights reserved. Keywords: Electroless deposition; Ni–P alloys; Composite coatings; Tungsten carbide (WC) 1. Introduction Electroless plating is a selective deposition plating process in which metal ions are reduced to a metallic coating by a reducing agent in solution. Plating takes place only on a suitable catalytic surface. Electroless plating offers a number of advantages over electroplating. High corrosion and wear resistance are the major reasons for the widespread use of electroless nickel (EN) deposits. The applications of EN include the fabrication of components for the automotive, oil and aircraft industries and also include the manufacture of electronic and computer equipment [1]. To enhance the properties of EN, reinforcement may be added to the solution to produce composite coating. The reinforcements or the second phase can be a hard oxide (Al 2 O 3 , SiO 2 ), carbide particles (SiC, WC) diamond or a solid lubricant (PTFE, graphite, MoS 2 ). Improvement in the wear resistance has been reported for electroless deposited Ni–SiC compo- site [1]. Several investigators have successfully codeposited hard particles (like Al 2 O 3 , SiO 2 ) in metal matrixes such as Ni–P [2–4]. Among the various engineering ceramics, Al 2 O 3 is one of the most widely used due to its high elastic modulus, high wear and chemical corrosion resistance and its strength reten- tion at high temperature [5,6]. Incorporation of Al 2 O 3 powder with electroless Ni–P alloys has been studied elsewhere and clarified the mechanism of codeposition of Al 2 O 3 [2,3]. The deposition of Ni–P composite on 6061Al alloy has been studied also to enhance its wear resistance and clarified the mechanism of codeposition of different ceramic powder in view of the zeta potential and free energy of adsorption. The electrolytic codeposition of WC particles with Ni matrix has been investigated by M. Stroumbouli et al. [7] and the electrochem- ical behavior of Ni–WC composite coatings on mild steel substrate has been evaluated by M. Sturender et al. [8]. In this present article, the Ni–P–WC composite was deposited using the electroless process. The effect of plating conditions on the codeposition of WC with Ni–P matrix was investigated. The distribution and the embedded percentage of WC particles in the metal matrix were examined as well as the Surface & Coatings Technology 201 (2007) 5948 – 5953 www.elsevier.com/locate/surfcoat ⁎ Corresponding author. Surface Protection and Corrosion Control Lab, Central Metallurgical Research & Development Institute, CMRDI, P.O.87 Hellwan, Cairo, Egypt. Tel.: +20122690782; fax: +2025010639. E-mail address: forzeinab@yahoo.com (Z.A. Hamid). 0257-8972/$ - see front matter © 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.surfcoat.2006.11.001