S.K. Seshadri

Wear resistance of nickel-fly ash composite coatings

Abstract Wear rates of nickel-fly ash composite coatings on mild steel have been measured for unlubricated rubbing against a rotating hardened steel disc. Wear losses of composite coatings were lower than those of nickel coating. The higher wear resistance of the composites may be attributed to the presence of fly ash, the excellent bonding between particles and matrix and the smearing-out of fly ash on both counterdisc and specimen. Optical and scanning electron microscopical investigations of the tested specimens were also carried out.

Tribological properties of cobalt-partially stabilized zirconia (PSZ) composites in dry sliding conditions

Particulate strengthened cobalt-partially stabilized zirconia composites were produced by conventional electro-codeposition method. Tribological properties of the deposits were evaluated against a hardened steel disc under dry sliding conditions on a thrust bearing type disc on disc machine. Dispersion of the particles improved the hardness and tribological properties of cobalt. Load and sliding velocity variations at the interface significantly influence the tribological properties of the deposits. Partially stabilized zirconia showed phase transformations during wear.

Corrosion characteristics of cobalt-silicon nitride electro composites in various corrosive environments

Abstract The corrosion characteristics of electro codeposited cobalt-silicon nitride composites in neutral sodium chloride and sulphuric acid solutions are presented. The electro composites showed greatly improved corrosion resistance over pure cobalt in nondeaerated 3.5% sodium chloride solution, but they induced significantly less galvanic corrosion on steel in the same medium. Galvanic current and dissolution current measurements showed a linear variation with the cathode-to-anode area ratio, while the galvanic potential showed a logarithmic variation with the same. Composites of cobalt-silicon nitride also showed improved passivation properties in 1 N sulphuric acid.

A model for wear rates of composite coatings

Abstract In the present investigation a model for wear rates of polymer-based composites is applied to predict the wear rates of nickel-silicon nitride composite coatings under sliding conditions. The measured wear rates seem to agree with the semiquantitative model.