Coatings For Industrial Applications Research Articles

Industrial applications of PACVD hard coatings

Transition metal nitride based hard coatings are widely applied in metal cutting, however, there are still drawbacks in metal forming processes limiting their implementation. The aim of this study is thus to discuss deposition processes suitable for coating of the often large and three-dimensional molds and dies used in metal forming. Furthermore, results obtained using different hard coatings in industrial applications for several case studies like aluminum pressure die-casting, plastics injection molding and sheet metal forming are presented and discussed. For best coating performance, a careful optimization of both substrate pre-treatment and coating deposition is necessary. The plasma-assisted chemical vapor deposition (PACVD) technique shows advantages for these applications because of the high flexibility in pre-treatment using chemical etching and plasma-nitriding, because of its ability to coat large complexly shaped tools and because of the possibility of deposition of low-chlorine containing low-friction coatings. Typical factors for the increase in lifetime in aluminum pressure die-casting are between 2 and 4, in plastics injection molding more than 10 and in deep drawing of 13 with respect to uncoated tools.

Recent trends in surface engineering using cathodic arc technique

The paper describes the developmental work of single layer and multilayer TiN, m-TiCN, (Ti,Al)N and m-(Ti,Al)N coatings for industrial applications (where the prefix ‘m’ stands for multilayer). The cathodic arc technique was used to deposit these coatings on high speed steel substrates (M2 grade) and cutting tools. For multi-layer m-TiCN deposition, (N 2+CH 4) gas mixture was used. For (Ti,Al)N and m-(Ti,Al)N coatings, sintered-TiAl targets with 70 at.% aluminum were used. Thickness, hardness, abrasive wear and adhesion strength of the coatings were measured for a large number of samples (∼50) from different cycles and average values are presented in this paper. X-Ray diffraction (XRD) measurements reveal that all the coatings have (111) orientation. (Ti,Al)N coating has a better oxidation resistance than the other coatings under investigation. The corrosion resistance of the coatings under investigations is found to be comparable, (Ti,Al)N being marginally superior amongst the coatings studied. Wear constant measured using Calo-wear equipment for TiN, m-(Ti,Al)N, m-TiCN, and (Ti,Al)N are 2.7, 1.9, 1.7 and 0.7×10 −13 m 2 N −1, respectively, indicating lowest wear resistance for TiN and highest for (Ti,Al)N amongst the coatings under investigation. A good correlation has been observed between the wear constant and the tool wear during machining.

A review on nanostructured WC–Co coatings

Unique mechanical properties of nanostructured materials motivate a worldwide interest to synthesize nanostructured coatings. Nanostructured WC–Co coatings have been extensively investigated because of the importance of WC–Co coatings in industrial applications, usually with respect to wear resistance requirements. The present paper has reviewed the studies in this field, including synthesis of nanostructured WC–Co powder, concern on decomposition of nanostructured WC particles, influence of spraying parameters on microstructure and mechanical properties of nanostructured coatings. Significant achievements in this field are: (1) It is possible to produce nanostructured WC–Co powders without non-WC/Co phases in quantities although a high percentage of non-WC/Co phases is frequently reported in conventional WC–Co powder; (2) By controlling agglomerate size of feedstock powder, fuel chemistry and fuel–oxygen ratio, the decomposition of WC particles can be reasonably eliminated so as to synthesize near nanostructured WC–Co coating with a low amount of non-WC/Co phases; and (3) Increased hardness, toughness and wear-resistance can be obtained in near nanostructured WC–Co coatings that are properly synthesized.