Oxidation control in atmospheric plasma spraying coating M.P.Planche ⁎ , H. Liao 1 , C. Coddet 2 LERMPS, UTBM,Sévenans, 90010 Belfort cedex, France Received 1 February 2007; accepted in revised form 17 April 2007 Available online 25 April 2007 Abstract Thermal spray coatings are formed by successive impingements and interbonding materials among the splats, solidified individual molten particles. Depending on the processing conditions employed during the spray process, deposits are produced with an asso and properties. This study highlights how the coating oxidation differences are influenced by the mechanisms involved du The commercial steel powder referenced Amdry XPT 512 is chosen for a systematic study of comparison across different s Steelparticles were sprayed with a F4 plasma torch and with a shrouded plasma spray process used in order to protect particles against atmospheric oxidation. The plasma jet was successively shielding by an inert gas shroud and by an oxidizing gas shroud. I post impact oxidation present in coatings are discussed in detail and the effects of these mechanisms on coating properties are addres The comparison was made on in-flight particle characteristics and on coating properties in terms of oxide content and porosity gas, in-flight characteristics are quite similarly independent of the nature of the shrouded gas. This way, the comparison o in the coatings corresponds to in-flight oxidation and is completely dependent on the nature of the shrouded gas. Compar obtained by APS, a decrease in both velocity and temperature of in-flight particles was observed leading also to a significa contents and to a slight increase in porosity level compared to coatings sprayed with air shrouding. © 2007 Elsevier B.V. All rights reserved. Keywords: Oxidation; Plasma spraying; In-flight particle characteristics; Gas shrouding 1. Introduction The improvement of the coating quality obtained by atmospheric plasma spraying (APS) involves a better under- standing of the phenomena occurring in thermal plasma jets. A great effort has been devoted to investigate the process including the effect of microstructure of sprayed coatings [1],in-flight particle properties [2] and process parameters on the resulting coating behaviour [3]. These studies indicated major factors controlling the in-flight particle properties and hence the coating properties. For example, an important aspectof thermally sprayed metal coatings is the oxidation during processing because the oxidation of thermally sprayed materials can nificantly influence the phase composition, the microstructure properties and therefore the performance of sprayed coa is clearly established that oxides within the coating chan deposit material properties as compared to bulk material some cases, these metal oxides are considered to improv properties like wear resistance or strength under compre loading [5,6]. Metal oxides residing along the splat bound can affectinter-splat cohesion whereas the oxideparticles dispersed in the splatcan also strengthen the splat[7,8]. Concerning stainless steel coatings, a low porosity and a low oxidation of these coatings were very important for a cor resistance application [9]. And, the interlamellar oxidatio great influence on the coating corrosion resistance [10]. Then,controlling thextentof oxideformation during spraying is important for microstructural control and for t useful to understand how and where the oxidation occurs spray process. When spraying into air, the reactive species, Available online at www.sciencedirect.com Surface & Coatings Technology 202 (2007) 69 – 76 www.elsevier.com/locate/surfcoat ⁎ Corresponding author. Tel.: +33 3 84 58 32 00; fax: +33 3 84 58 32 74. E-mail addresses: marie-pierre.planche@utbm.fr (M.P. Planche), hanlin.liao@utbm.fr (H. Liao), christian.coddet@utbm.fr (C. Coddet). 1 Tel.: +33 3 84 58 32 42; fax: +33 3 84 58 32 74. 2 Tel.: +33 3 84 58 30 24; fax: +33 3 84 58 32 74. 0257-8972/$ - see front matter © 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.surfcoat.2007.04.053