23. - 25. 10. 2012, Brno, Czech Republic, EU CORROSION PROPERTIES OF CERMET COATINGS SPRAYED BY HIGH-VELOCITY OXYGEN-FUEL Dragos UŢU, Iosif HULKA, Viorel-Aurel ŞERBAN, Hannelore FILIPESCU “Politehnica” University of Timisoara, Romania, dragosutu@yahoo.com, hulka_iosif@yahoo.com, viorel.serban@rectorat.upt.ro, hannelore.filipescu@yahoo.com Abstract High velocity oxygen fuel (HVOF) is one of the most promising coatings deposition method used in many industrial applications as: aerospace, automation, transportation and power generation system. The paper presents the experimental results regarding the corrosion behavior of different sprayed cermet powders WC CoCr and WC CrC Ni deposited on disc-like C45 steel specimens tested in a NaCl aqueous solution. The powders and coatings morphology were analyzed by scanning electron mi croscopy (SEM), the phase’s identification was performed by X-Ray diffraction technique (XRD). In order to evaluate the quality of the HVOF obtained coatings the porosity of the specimens was determined. The polarization curves were obtained using the potentiodynamic polarization testing method and a three electrode open cell. The results showed that the both coatings had a good corrosion behavior. However, the overall corrosion resistance of the WC–CrC–Ni coating was inferior to that of the WC–Co–Cr coating. Keywords: cermet coating, HVOF spraying method, corrosion behavior 1. INTRODUCTION In the process industry, hydroelectric power plants, in offshore piping the materials are very often exposed to environments that are corrosive which can affect the lifetime of the components and produce high maintenance costs [1]. It is already known that the practice of applying thermal sprayed coatings onto the surface of components which operate in aggressive media can prevent their surface degradation by corrosion, erosion or combined erosion-corrosion. The ability of these coatings to protect the base metal against corrosion is given by their composition, morphology and structure. Microstructural features which enhance the corrosion resistance include high density, low porosity, small grain size, absence of the cracks [2]. The high velocity oxygen fuel (HVOF) spraying process is one the most promising deposition method in order to obtain excellent quality coatings with low porosity, good bond strength and high density. Generally, this technique of thermal spraying can be used as a hard-chrome alternative as well as for new applications where thermal spraying was not put into account due to cost and technical reasons [3]. The present paper studies the corrosion behavior in 1M NaCl aqueous solution of thermally sprayed cermet powders WC CoCr and WC CrC Ni deposited on disc-like C45 steel specimens. 2. EXPERIMENTAL PROCEDURE The materials used for investigations were two different fine sinterized powders: WC-Co-Cr with the nominal composition 86%WC-10%Co-4%Cr and WC-CrC-Ni having the composition 77%WC-20%CrC-7%Ni, the powder particle size being in range -10+2 µm. Both powders were HVOF sprayed, using an ID Cool Flow gun from Thermico firm, Germany, on disc-like C45 carbon steel substrates which were previously degreased with acetone and gritblasted with corundum at