1 INFLUENCE OF THE MICROSTRUCTURE ON CORROSION INDUCED DAMAGE OF WC-Co CEMENTED CARBIDES G. Fargas 1 *, C.M. Müller 2 , D. Sosa 3 , J. Tarragó 1 , E. Tarrés 4 , J. Fair 4 , L. Llanes 1 1 CIEFMA/EEBE, Departament de Ciència dels Materials i Enginyeria Metal·lúrgica, Universitat Politècnica de Catalunya, Barcelona, Spain 2 ELECTRODEP, Departament de Ciència dels Materials i Química Física, Universitat de Barcelona, Spain 3 INTEMA-CONICET, División Metalúrgica, Universidad Nacional de Mar de Plata, Argentina 4 SANDVIK HYPERION, Coventry, UK e-mail: gemma.fargas@upc.edu ABSTRACT The main goal of the present work is to study the influence of the microstructure on the corrosion behavior of cemented carbides WC-Co in two corrosive media: seawater and mine water. Thus, two grades with the same proportion of cobalt as a binder and different grain size: medium and ultrafine were selected. Corrosion kinetics were determined by immersion tests while the electrochemical evolution of the surface was analyzed using impedance testing. Damage tolerance to corrosion was evaluated by assessing fracture strength on specimens previously subjected to corrosion. Results pointed out that for both grades the corrosion rate was higher in sea water, being more significant for the grade with a medium grain size. The corrosion phenomenon that took place in both media was caused by the oxidation reaction of cobalt. In sea water, the polarization resistance decreased for both grades whereas in mine water increased, due to the formation of a layer of corrosion products which slowed down the cobalt dissolution process in surface. In both media, a greater strength loss of the ultrafine grade was evidenced. Keywords: cemented carbides, corrosion kinetics, seawater, mine water INTRODUCTION Cemented carbides are a group of powder metallurgy liquid-phase-sintered materials consisting of brittle refractory carbides embedded in a metallic matrix that acts as a binder. As a consequence of their fully interpenetrated two-phase structure, cemented carbides exhibit an outstanding combination of hardness, wear resistance, strength and toughness. This unique combination of properties has established cemented carbides at the forefront of a wide range of engineering and tooling applications operating under extremely demanding service conditions [1]. However, cemented carbides suffer from different in-service degradation phenomena that seriously affect the performance and service-life of engineering parts. Among them corrosion stands out. Corrosion may develop in a large number of applications where cemented carbides are exposed to chemically aggressive media, including a wide variety of corrosive environments, such as lubricants, chemical and petrochemical products, mine and sea waters [2,3,4]. Corrosion damage may induce a detrimental effect on the strength and fatigue resistance of cemented carbides due to the formation of corrosion pits with pronounced stress Manuscript Click here to download Manuscript fargas_O53_English.docx 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65