DI-UMONS : Dépôt institutionnel de l’université de Mons

Recherche transversale
(titres de publication, de périodique et noms de colloque inclus)
2016-10-12 - Colloque/Présentation - communication orale - Anglais - 1 page(s)


  • Codes CREF : Résistance et comportement des matériaux (DI2110)
  • Unités de recherche UMONS : Métallurgie (F601)
  • Instituts UMONS : Institut de Recherche en Science et Ingénierie des Matériaux (Matériaux)
  • Centres UMONS : Ingénierie des matériaux (CRIM)

Abstract(s) :

(Anglais) INTRODUCTION The principle of electroless deposition has been first discovered in the 19th century but the first practical application of the method was reported by Brenner and Riddell in 1946[1]. Electroless nickel–boron alloys (that have borohydride ion or amine–borane compounds as the reducing agent) are the second most used electroless nickel alloys. When compared with nickel-phosphorous coatings, electroless nickel-boron deposits present superior mechanical properties, a much higher hardness (up to 900 hv100 against 500 to 700 hv100)[2], better wear and scratch resistances [3–9] [10–13]. Electroless Ni–B coatings are more wear resistant than tool steel and hard chromium coatings. Also, they can be used to replace expensive materials such as gold and silver in electronic industries. Applications in electronic industries require excellent property with really thin and precise thickness. As the coating thickness may influence all the coating properties, the aim of this study is to enable a more comprehensive analysis of the changes in surface hardness and wear behavior introduced by different coating thicknesses. ELECTROLESS NICKEL COATINGS PREPARATION The substrate samples used for this study were (25 * 25 * 2 mm) mild steel sheets (St 37). Before plating, all samples were gound with 500 and 1200 MESH silicon carbide abrasive paper; degreased with acetone; etched in 30 vol.% HCl and rinsed with deionized water before direct immersion in the electroless nickel-boron plating bath for different plating times (5, 10, 15, 20, 25, 30, 60, 90 minutes). The plating bath was based on Delaunois’ formulation and parameters [4]. It operates at 95 ± 1 in a one-liter cell with controlled mechanical agitation at 300rpm. COATING CHARACTERIZATION A Scanning Electron Microscope (Hitachi's SU8200) was used to study the cross section morphology and measure the coating thickness. A microhardness tester (Mitutoyo HM-200) equipped with Vickers indenter was used for hardness measurement. They were carried out on the specimens' surface under different loads : 10gf, 50gf and 100 gf; with a load exertion time of 20 s. The tribological behavior of the samples was investigated using a pin-on-disk CSM microtribometer (in unlubricated conditions), where the coated samples served as the disks and the counterparts were 6mm diameter alumina balls with hardness of 1400 HV. The sliding speed and sliding distance were, respectively, 10cm/s and 50m in the case of ultrasound-assisted electroless Ni-B. Wear tests were carried out under normal loads of 10 N. Figure 1: Hardness characterization method in samples surface. CONCLUSION In view of being able to use the significant mechanical properties of nickel boron in thin coatings applications, a study about the influence of thickness on the surface hardness and wear behavior was developed. The specific wear rate (Ws) decreased slightly with the increase of thickness: thicker coating presented thus better wear behavior. However, the coefficient of friction did not change with thickness. The superficial hardness varies with the thickness, due to the influence of the substrate in the case of thinner materials. Coatings that are thicker than 10µm did no present any influence of the substrate for Vickers indentation with load up to 100gf. Références [1] a. Brenner, G.E. Riddell, Nickel plating on steel by chemical reduction, J. Res. Natl. Bur. Stand. (1934). 37 (1946) 31. doi:10.6028/jres.037.019. [2] V. Vitry, A. Sens, F. Delaunois, Comparison of Various Electroless Nickel Coatings on Steel: Structure, Hardness and Abrasion Resistance, Mater. Sci. Forum. 783-786 (2014) 1405–1413. doi:10.4028/www.scientific.net/MSF.783-786.1405. [3] F. Delaunois, P. Lienard, Heat treatments for electroless nickel – boron plating on aluminium alloys, Surf. Coatings Technol. 160 (2002) 239–248. doi:10.1016/S0257-8972(02)00415-2. [4] F. Delaunois, J.P. Petitjean, P. Lienard, M. Jacob-Duliere, Autocatalytic electroless nickel-boron plating on light alloys, Surf. Coatings Technol. 124 (2000) 201–209. doi:10.1016/S0257-8972(99)00621-0. [5] V. Vitry, F. Delaunois, Formation of borohydride-reduced nickel–boron coatings on various steel substrates, Appl. Surf. Sci. 359 (2015) 692–703. doi:10.1016/j.apsusc.2015.10.205. [6] V. Vitry, F. Delaunois, C. Dumortier, How heat treatment can give better properties to electroless nickel-boron coatings, Metall. Ital. 101 (2009). [7] V. Vitry, F. Delaunois, C. Dumortier, Mechanical properties and scratch test resistance of nickel-boron coated aluminium alloy after heat treatments, Surf. Coatings Technol. 202 (2008) 3316–3324. doi:10.1016/j.surfcoat.2007.12.001. [8] V. Vitry, F. Delaunois, Nanostructured electroless nickel-boron coatings for wear resistance, Anti-Abrasive Nanocoatings. (2015) 157–199. doi:10.1016/B978-0-85709-211-3.00007-8. [9] V. Vitry, A. Sens, A. Kanta, F. Delaunois, Experimental study on the formation and growth of electroless nickel- boron coatings from borohydride-reduced bath on mild steel, (n.d.) 1–21. [10] T.S.N. Sankara Narayanan, S.K. Seshadri, Formation and characterization of borohydride reduced electroless nickel deposits, J. Alloys Compd. 365 (2004) 197–205. doi:10.1016/S0925-8388(03)00680-7. [11] B. Oraon, G. Majumdar, B. Ghosh, Improving hardness of electroless Ni-B coatings using optimized deposition conditions and annealing, Mater. Des. 29 (2008) 1412–1418. doi:10.1016/j.matdes.2007.09.005. [12] K.H. Lee, D. Chang, S.C. Kwon, Properties of electrodeposited nanocrystalline Ni-B alloy films, Electrochim. Acta. 50 (2005) 4538–4543. doi:10.1016/j.electacta.2004.03.067. [13] K. Krishnaveni, T.S.N. Sankara Narayanan, S.K. Seshadri, Electroless Ni-B coatings: Preparation and evaluation of hardness and wear resistance, Surf. 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