ORIGINAL ARTICLE Ferrochromium slag as a protective coating material against oxidation for caster rolls Yilmaz Kucuk 1 | Mecit Oge 1 | Mustafa Sabri Gok 1 | Abdullah Cahit Karaoglanli 2 1 Department of Mechanical Engineering, Faculty of Engineering, Bartin University, Bartin, Turkey 2 Department of Metallurgical and Materials Engineering, Faculty of Engineering, Bartin University, Bartin, Turkey Correspondence Mecit Oge Email: mecitoge@bartin.edu.tr Funding information T€ urkiye Bilimsel ve Teknolojik Aras ßtirma Kurumu, Grant/Award Number: 113M178 Abstract In this study, ferrochromium (FeCr) slag, which is available as an industrial waste, is proposed as a protective surface coating material particularly for protec- tion of continuous casting rolls against oxidation. FeCr slag was successfully deposited with atmospheric plasma spray (APS) method. Before the coating pro- cess, FeCr slag powder prepared in the particle size range of 5-38 lm, was inves- tigated using conventional characterization methods (XRD, SEM, TGA etc.). Thermal Barrier Coating (TBC) system was used as a basis for deposition pro- cesses. Accordingly, NiCoCrAlY (Amdry, 45 + 5 lm) was firstly deposited as metallic bond coat layer onto the surface of AISI 420 substrate, and then FeCr slag layer was deposited as the top coating layer. After the deposition of FeCr slag powder, the resulting coating layer was found to have low porosity with a homogeneous microstructure. The deposited FeCr slag coatings were subjected to isothermal oxidation tests at different temperatures and test durations for determi- nation of their oxidation behavior and upper operating temperature limits. The results obtained from this study indicate that FeCr slag can be considered as an alternative protective coating material for caster rolls which are subjected to high temperatures up to 800°C. KEYWORDS coatings, oxidation, plasma spraying, Slags 1 | INTRODUCTION Since 1970s, thermal spraying method has been widely applied for surface coating of rollers used in continuous casting process in the iron-steel production industry. Con- tinuous casting is a method widely adopted by steelmakers in mass production of steel. During the continuous casting process, the molten metal is solidified into a “semi-fin- ished” billet, bloom, or slab for subsequent rolling in the finishing mills. In continuous casting process, caster rolls are utilized as serial support rollers to convey the solidified steel ingots. 1-6 As cooling water is sprayed on the surface of caster rolls, oxidation, and corrosion-induced damages as well as the thermal cracks occur. 7,8 Another application for oxidation-related service conditions is the thermal barrier coatings (TBCs). TBCs have structural and functional characteristics which render them an important ceramic coating material especially in areas such as, aircraft, turbine blade, and other hot-section components against oxida- tion, corrosion, wear, and impact erosion. 9-14 TBCs are usually composed of a metallic bond coat and a ceramic top coat. The bond coat is usually composed of MCrAlY (M = Ni and/or Co) and used against thermal expansion coefficient (TEC) mis- match between the metallic substrate and the ceramic layer. The top coat (ceramic layer) usually consists of 8 wt% Y 2 O 3 par- tially stabilized zirconia (YSZ) and it has an important role in reducing high-temperature-induced failure mechanisms under the service conditions mentioned above. Received: 11 January 2018 | Accepted: 19 January 2018 DOI: 10.1111/ijac.12875 Int J Appl Ceram Technol. 2018;1–8. wileyonlinelibrary.com/journal/ijac © 2018 The American Ceramic Society | 1