B. Subramanian

Evaluation of corrosion and wear resistance titanium nitride (TiN) coated on mild steel (MS) with brush plated nickel interlayer

Abstract Titanium nitride (TiN) coatings were deposited on mild steel (MS) by direct current reactive magnetron sputtering. With the aim of improving the corrosion resistance of TiN, an additional nickel interlayer was brush plated on the steel substrates before TiN film formation. The phases have been identified with X-ray diffraction analysis. The hardness values of TiN layers were found to increase with the increase in thickness of the Ni interlayer. The wear track investigations of TiN layers showed that the TiN/MS system was worn out by abrasive wear mechanism while on the film with Ni interlayer is by adhesive wear. It was found that the TiN/Ni/MS stack had a weaker tendency towards corrosion and higher corrosion resistance in 3·5%NaCl than the bare MS substrate, Ni/MS and TiN/MS specimen.

Electrodeposition of zinc–nickel alloy by pulse plating using non-cyanide bath

Abstract In this study, zinc–nickel electrodeposition was carried out in a sulphamate bath at pH 3–4 by pulse plating and the deposits obtained were characterised by measuring microhardness, surface roughness and by employing SEM, XRD, AFM techniques. The corrosion behaviour of the deposits was evaluated by potentiodynamic polarisation. The deposits obtained by pulse plating have an increased Ni content, thought to be responsible for an improved corrosion resistance.

Preparation of chromium oxynitride and chromium nitride films by DC reactive magnetron sputtering and their material properties

Abstract Thin films of ∼2 μm thick chromium nitride (CrN) were prepared by direct current (dc) reactive magnetron sputter deposition on steel substrates. XPS spectra showed the presence of chromium in the form of CrN with traces of Cr2O3 on CrN thin films. XRD spectrum shows CrN peaks at 37 and 43° which corresponds to (111) and (200) planes. Surface topography from atomic force microscope shows that films have continuous coverage of rectangular cell like patterns. Corrosion performance of these films on low carbon steel substrates in 3·5%NaCl solution was evaluated using electrochemical techniques. A less negative value of Ecorr and lower value of Icorr signify an improvement in corrosion resistance of the CrON coating. Scanning vibrating electrode technique (SVET) was able to discretely map relative cathodic and relative anodic sites at a macroscopic defect and to record the changes of local electrode activities in a real time.

Effects of deposition temperature on materials properties of magnetron sputtered titanium nitride coatings on mild steel substrates with Ni interlayer

Abstract Titanium nitride (TiN) coatings were prepared on mild steel (MS) substrates by the direct current reactive magnetron sputtering. With the aim of improving the adhesion of TiN layer, an additional nickel interlayer was brush plated on the MS substrates before TiN coating formation. The phase has been identified with X-ray diffraction analysis and the results show that the prominent peaks observed in the diffraction patterns correspond to the (111), (200) and (222) planes of TiN. Cross-sectional SEM indicated the presence of columnar structure. The mechanical properties such as modulus and hardness of these films were characterised by the nanoindentation technique.

Materials properties of electrodeposited NiFe and NiCoFe coatings

Abstract The codeposition behaviour of the electrodeposited iron group alloy system, NiFe and NiCoFe, was studied in acid sulphate electrolyte. X-ray diffraction measurements revealed the existence of FCC phases. X-ray fluorescence analysis of the elemental composition in NiFe and NiCoFe coatings electrodeposited over copper substrate was also carried out. The result suggested that Ni is inhibited by the presence of Fe2+ and Co2+ ions. The properties of soft magnetic NiFe and NiCoFe coatings electrodeposited in the presence of saccharin and sodium lauryl sulphate additives were studied. Corrosion performance of these coatings in 3·5% NaCl solution was evaluated using impedance electrochemical techniques. The superior coefficient of friction of NiFeCo coatings was observed from block-on ring test.

Surface characterisation studies of nickel-chromium PVD: EB evaporated low carbon steel samples

Abstract Increasing concern over toxic wastes produced by nickel–chromium (Ni–Cr) plating industries has resulted in strong research efforts to replace conventional plating by physical vapour deposition techniques like evaporation and sputtering. Ni–Cr coatings on mild steel substrates produced by an electron beam evaporation process with layer thickness of ∼8–10 m m have been investigated with regard to the structural and corrosion properties. The structure of the coating was evaluated by X-ray diffractometer (XRD). The (110) Cr and (200) Ni predominant peaks with the crystallite size in the range of 25–30 nm was observed from XRD pattern. The electrochemical polarisation studies performed on samples showed the corrosion resistant nature of the evaporated Cr coating with Ni underlayer on mild steel substrates. Atomic force microscopy (AFM) and scanning electron microscopy (SEM) were used to investigate the surface characteristics of the samples before and after the electrochemical corrosion tests. The localised corrosion through a micropore in the evaporated Cr deposit and its penetration to the Ni layer was observed from SEM. The smaller change in roughness observed from AFM reflects the resistance of this coating to corrosion breakdown.

Sequential deposition of Cu–Ni by electron beam evaporation and its characterisation

Abstract Sequential deposition of Cu–Ni was carried out on glass and mild steel substrates by electron beam evaporation technique. The films were vacuum annealed at 200°C for 1 h. A smooth deposit with 7·8 μm thickness was observed using a profilometer. The polycrystalline nature with FCC structure of the films was determined with X-ray diffraction analysis. The uniform coverage of film surface was observed with atomic force microscopy (AFM). X-ray fluorescence (XRF) showed a change in composition for the vacuum annealed Cu–Ni film. A high transmittance in the visible region and a very low transmittance in the infrared region were observed for these films. Corrosion behaviour of the evaporated Cu–Ni films in 3·5% w/v NaCl solution was examined.