XRD characterisation of composite Ni-based coatings prepared by electrodeposition L. Tarkowski ⇑ , P. Indyka, E. Bełtowska-Lehman Institute of Metallurgy and Materials Science of Polish Academy of Sciences, Reymonta 25, Kraków, Poland article info Article history: Available online 11 August 2011 Keywords: Residual stresses Crystallographic texture Crystalline size Electrodeposition abstract The present work is aimed at XRD investigation of structural parameters that influence the functional prop- erties of Ni–W/Al 2 O 3 electrodeposit coatings. The relationship between electrodeposition parameters and structural properties of the coatings deposited on steel substrates has been determined. XRD investigations were performed on a Bruker D8 Discover diffractometer equipped with a position-sensitive linear detector. The modified sin 2 w X-ray diffraction method was used to determine the macroscopic residual stresses of deposits. The crystallite size and lattice strain of the coatings were evaluated by analysis of X-ray diffraction patterns (Rietveld analysis). The crystallographic texture was analysed using the orientation distribution function (ODF) calculated from the incomplete pole figures. It was shown that the structural properties of the deposits were strongly correlated with chemical composition. X-ray diffraction patterns of all Ni– W coatings exhibit mainly the fcc phase structure of the Ni–W solid solution with a lattice parameter inter- mediate between those of Ni and W, which rises when the tungsten content increases. At the same time the crystallite dimension (the size of the coherent domains) was gradually reduced. It was found that Ni–W coatings containing about 40 wt.% W revealed the tensile residual stresses (2300–1200 MPa), depending on deposition conditions. Ó 2011 Elsevier B.V. All rights reserved. 1. Introduction Metal Matrix Composite (MMC) materials composed of ceramic particles embedded in a metal matrix have received much attention due to outstanding improvements of mechanical properties and a high possibility for application to functional materials [1]. One of the methods of preparing such composites is a relatively simple and low-cost electrochemical deposition. In recent years much ef- fort has been spent searching for alternatives to electroplated hard chromium coatings which are widely applied commercially to pro- vide enhanced surface performance [2]. Despite the excellent prop- erties of the hard chromium, used in automotive and aviation industries, they should be eliminated from the manufacturing pro- cess (in accordance with EU directives) due to high toxicity and car- cinogenicity of hexavalent chromium [3]. Up to now, only electroless Ni–P coatings have found use in select applications [4]. The important alternative to hard Cr could offer electroplated Ni- based alloys or composites containing refractory metal (molybde- num or tungsten) [5]. It is well known that the functional properties of the materials are mainly controlled by their composition and microstructure. Therefore, hard particles (oxides, carbides) incorpo- rated into a Ni-based deposit can enhance technical parameters of such material, including its mechanical (plasticity), tribological (adhesion, wear resistance) and corrosion resistance properties [6]. Hence, this work is focused on XRD investigation of structural parameters that influence the functional properties of Ni–W/Al 2 O 3 co-deposited coatings, including macroscopic residual stresses, crystallographic texture and crystallite size. 2. Experimental procedure Diffraction experiments were performed in the Laboratory of X-ray Diffraction in the Institute of Metallurgy and Materials Sci- ence using a Bruker D8 Discover equipped with an Eulerian cradle. CoK a filtered radiation, formed by multi-capillary optics provided a near parallel primary beam with diameter of 1 mm. The diffracted beam was detected using a position sensitive linear detector. A residual stress measurement was performed in psi-geometry, which means that the sample was tilted around an axis parallel to the plane of the diffractometer. Experimental data were analysed with the software developed at the Institute of Metallurgy and Materials Sciences of the Polish Acad- emy of Sciences in Krakow [7–9]. Residual stresses analysed in the measured areas of the sample were calculated on the basis of a re- cent approach in the field [10]. Crystalline sizes were calculated using Rietveld algorithms in MAUD software [11]. 3. Material Ni–W/Al 2 O 3 coatings were electrodeposited from sulphate-cit- rate electrolytes [5], into which Al 2 O 3 nanopowder of variable amounts (40–80 g/dm 3 ) were added. The electrolysis was carried 0168-583X/$ - see front matter Ó 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.nimb.2011.07.108 ⇑ Corresponding author. E-mail address: leszek.tarkowski@gmail.com (L. Tarkowski). Nuclear Instruments and Methods in Physics Research B 284 (2012) 40–43 Contents lists available at SciVerse ScienceDirect Nuclear Instruments and Methods in Physics Research B journal homepage: www.elsevier.com/locate/nimb