Effects of Nitrocarburisation on Characteristics of Electrodeposited Co–w–ti–al 2 O 3 Composite Coating

The significance and theoretical basis of the strengthening process of electrodeposited Co–W–Ti–Al₂O₃ composite coatings and nitrocarburisation are briefly explained. The conditions of the composite process and the characteristics of the composite heat treated coatings are studied in detail. Co–W–Ti–Al₂O₃ composite coatings with good characteristics are obtained on steel when the appropriate complex agent and additives are selected and the conditions of the composite electrodeposition process are controlled. The hardness and wear resistance of the composite coatings after nitrocarburising are much better than those of the composite without nitrocarburisation. The hardness of the nitrocarburised Co–W–Ti–Al ₂O₃ composite is found to decrease gradually from the surface into the internal layer. X-ray diffraction shows that the diffused coating contains a solid solution of cobalt, titanium carbide, titanium nitride, tungsten carbide, tungsten nitride and alumina, together with a little r-(FeCo), when the Co–W–Ti–Al₂O₃ composite coating is nitrocarburised. SE/514