Progress in Surface Treatment and Processing of Coatings

Abstract

The surface treatments of materials and processing of coatings are becoming increasingly important for imparting functional properties, repairing the surfaces, and protecting the surfaces from conditions of stress, temperature, and corrosive media. The processing approaches involving surface cleaning and finishing, plating and electroplating, dip and conversion coatings, vacuum and controlled atmosphere coatings, surface modification using high-energy and particle beams (laser surface processing and ion implantation), and heat treatments (flame, induction, and high-energy beams) have all been successfully implemented to improve the surface properties and functionalities of materials. The advancements in the surface treatments and coatings processing have kept pace with the advances in the materials development. Novel processes have been regularly introduced and the existing processes have been continuously adapted for surface engineering of materials that are becoming increasingly important in new design considerations. The surface engineering of light alloys, ceramics, and amorphous/nanostructured materials is gaining unprecedented momentum. Metallurgical (interfacial bonding, elemental redistribution, and defects/porosity/cracking), manufacturing (noncontact, rapid, and flexible processing), environmental (eco-friendly and benign processing), and health (nontoxic materials and processing) considerations are becoming increasingly important in the surface treatments and processing of coatings. The TMS Surface Engineering Committee regularly organizes symposia in TMS/Materials Science & Technology (MST 16–20 March 2014), the committee organized a symposium titled Advances in Surface Engineering: Alloyed and Composite Coatings III. The symposium featured 49 presentations including nine invited talks in the areas of processing (thermal spray, laser, and friction stir, and electrochemical processing) and properties (wear, oxidation/corrosion, mechanical, and high-temperature properties) of alloy and composite coatings. The Surface Engineering Committee also organized two joint sessions titled ‘‘Recent Developments in Biological, Electronic, and Functional Thin Films and Coatings’’ with the TMS Thin Films and Interfaces Committee. The joint sessions featured an additional 23 presentations including four invited talks on the topics coatings for biomedical applications, multilayer coatings, anticorrosive coatings, and thin films. The committee encourages the participation of industry in its programming. In addition to the presentations by university researchers and students, the symposium also featured several talks by researchers working in industry and government research laboratories. The committee recognizes the importance of partnership between the universities and industries in advancing the state-of-the-art in the areas of surface engineering. The committee is committed to organizing regular symposia and publishing feature issues to provide a platform for useful discussions on evolving topics in surface engineering. This issue of JOM presents five articles, including four articles based on presentations made at the TMS 2014 Annual Meeting on the topics of surface treatment and processing of coatings. In the article titled ‘‘Aqueous Corrosion Behavior of Micro Arc Oxidation (MAO)-Coated Magnesium Alloys: A Critical Review,’’ L. Rama Krishna and G. Sundararajan examine the prospects of the relatively novel and eco-friendly micro-arc oxidation (MAO) process in aqueous corrosion protection of Mg and its alloys. The authors present a critical review of the influence of MAO processing parameters such as electrolytic composition, presence of insoluble additives in the electrolytes, electrical parameters, and substrate composition on the corrosion resistance of Mg alloys. The authors conclude that the MAO process offers distinct advantages such as complete crystalline structure, good coating-substrate bonding, and the ability to tailor Sandip P. Harimkar is the guest editor for the Surface Engineering Committee of the TMS Materials Processing & Manufacturing Division, and coordinator of the topic Surface Engineering of Materials in this issue. JOM, Vol. 66, No. 6, 2014