Wear mechanism of Ni–P–BN(h) composite autocatalytic coatings O.A. Leo ´n a, * , M.H. Staia b , H.E. Hintermann c a Polytechnic Experimental National University (UNEXPO), Puerto Ordaz, Estado Bolı ´var, Venezuela b School of Metallurgy and Materials Science, Central University of Venezuela, Caracas, Venezuela c University of Neuchatel, Neuchatel, Switzerland Available online 4 October 2005 Abstract Sliding wear experiments at room temperature were performed, using a pin-on-disc configuration, in order to study the wear mechanism of autocatalytic composite Ni – P – BN(h) coatings deposited on AISI 316L stainless steel against AISI 52100 steel balls. Coatings with 11, 35, 45 and 67 vol.% BN(h) were obtained by dispersing the BN(h) of an average particle size of 5.16 Am in a sodium hypophosphite based autocatalytic bath with enhanced agitation and surfactant addition. Scanning Electron Microscopy and 3D perfilometry techniques were employed to study the wear scars. Knoop microhardness, roughness, friction coefficients and wear resistance of the coatings for all experimental conditions are also reported. The results obtained indicate that, in the case of coatings with BN(h) content higher than 11 vol.%, the wear mechanism is a mild adhesive wear mechanism (adhesive ploughing) with high plastic strain of the coatings and low coating transfer to the ball. Coatings with 11 vol.% BN(h) show a mixed mechanism of adhesive and abrasive wear. D 2005 Elsevier B.V. All rights reserved. Keywords: Wear mechanism; Ni – P – BN(h) composite; Autocatalytic coatings 1. Introduction The incorporation of finely sized particles within Ni–P autocatalytic coatings greatly increased their properties and, in some cases, added entirely new features to the coatings performance, which increased their use in different indus- tries from high technology (such as electronic components and computers) and to more traditional industries (such as general mechanics, automobile, paper mills, textile and food). Composite coatings with hard particles as SiC, diamond, Al 2 O 3 , WC, Si 3 N 4 or BN(cubic) were produced to increase the wear resistance and hardness of surfaces. Enhanced lubricity was achieved by incorporating PTFE, MoS 2 or BN(h) soft particles [1–4]. Recently the authors have been carrying out experiments related to the incorpo- ration of BN(h) particles in Ni–P autocatalytic coatings [5– 7]. These composite coatings in as-deposited and hardened conditions were tested in a pin-on-disc tribometer at room temperature. The results showed that the Ni–P–BN(h) coating in the as-deposited condition have a wear resistance two orders of magnitude higher than the Ni–P coating. Moreover, the chemical and thermal stability of the BN(h) allow the use of any post-heat treatment in order to impart adequate hardness [6]. The wear mechanism at room temperature reported for the Ni–P–BN(h) composite autocatalytic coatings, tested against alumina [5] and AISI 52100 [6,7], corresponds to a purely adhesive wear process, but at the moment, a systematic study of the wear mechanism of these new Ni–P–BN(h) autocatalytic coat- ings is unavailable in the literature. Therefore, the present study was conducted with the aim of evaluating the wear mechanism of Ni–P–BN(h) autocatalytic coatings with 11, 35, 45 and 67 vol.% BN(h) when tested with a pin-on-disc configuration at room temperature. 2. Experimental Details on the AISI 316L stainless steel samples dimensions, conditioning of the surface prior deposition and the deposition process have been adequately described 0257-8972/$ - see front matter D 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.surfcoat.2005.08.061 * Corresponding author. E-mail address: oleonl@intercon.net.ve (O.A. Leo ´n). Surface & Coatings Technology 200 (2005) 1825 – 1829 www.elsevier.com/locate/surfcoat