Comparison of the structure and chemical composition of crystalline and amorphous electroless Ni-W-P coatings

• Published in: Journal of the Electrochemical Society Vol. 151; no. 6; pp. C385 - C391
• Main Authors: VALOVA, E, ARMYANOV, S, FRANQUET, A, PETROV, K, KOVACHEVA, D, DILLE, J, DELPLANCKE, J.-L, HUBIN, A, STEENHAUT, O, VEREECKEN, J
• Format: Journal Article
• Language: English
• Published: Pennington, NJ Electrochemical Society 2004
• Subjects: Cross-disciplinary physics: materials science; rheology; Electrodeposition, electroplating; Exact sciences and technology; Materials science; Methods of deposition of films and coatings; film growth and epitaxy; Physics; Amorphous material; Atomic force microscopy; Surface segregation; Ternary compounds; Electroless deposition; Transition elements Compounds; Photoelectron spectroscopy; Surface structure; Tungsten phosphides; Crystalline material; Nickel phosphides; Chemical composition; Grain boundary segregation
• ISSN: 0013-4651; 1945-7111
• DOI: 10.1149/1.1705661

Electroless deposition was applied to prepare Ni-W-P coatings of two types: crystalline, with low P and W, and amorphous with high W content. Their morphology was studied by atomic force microscopy. Polycrystalline Ni-W-P alloys consist of grains of stacked plates (lamellas), as it was revealed by transmission electron microscopy. The coatings exhibit a (100) texture. X-ray diffraction and electron diffraction analysis demonstrated the unit cell parameter of the crystalline phase in Ni-W-P is practically equal to that of pure Ni. This implies W and P are localized along the grain boundaries. The Warren/Averbach method was applied to determine microstrain and size of coherent scattering domains. The crystalline structure promotes the surface oxidation of Ni-W-P to higher extent in comparison with the amorphous structure. X-ray photoelectron spectroscopy analysis demonstrated the presence of oxygen and carbon in the bulk of the crystalline Ni-W-P coatings in larger quantities than in the amorphous. In the crystalline coatings in addition to oxygen and carbon, scanning Auger electron spectroscopy showed the presence of nitrogen. It is supposed that all these elements come from ligand residues adsorbed at the grain boundaries during coating growth. Nanoindentation tests indicated that amorphous Ni-W-P samples display more uniform surface mechanical properties at the nanometer scale than the crystalline ones. [Substrate: Al alloy].