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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.

Laser processed Si coatings with thickness in the range 100–150 μm were produced on AISI type 316L stainless steel substrate using a continuous wave CO2 laser. The experiments were done at a laser power between 1·5 kW and 1 kW, process speeds in the range 33·6–8·3 mm s−1, with a beam diameter of 1·6 mm. The microstructure of the laser processed coating consists of columnar dendrites and fine cellular structures. High temperature phases such as δ-ferrite and γ-austenite were found on the resolidified microstructure. The microanalysis technique demonstrated that the laser clad zone possessed a high concentration of Si. The crack free laser clad zone exhibited high hardness in the range 850–900 HV.

Laser surface alloying (LSA) of AISI 316L stainless steel with various compositions of Ni and SiC for different laser parameters was investigated. The hardness of the LSA layer was found to be a strong function of silicon content. The maximum hardness achieved was 733 HV. Columnar dendrites, equaxial dendrites and cellular structure were observed in the resolidified microstructure. XRD and EPMA studies were used to find different phases and elemental concentration, respectively.