Influence of Fracture Toughness and Microhardness on the Erosive Wear of Cermet Coatings Deposited by Thermal Spray
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TRODUCTION
WEAR is one of the most important and common problems that occur in the industries. This phenomenon affects not only the life of the components of equipment and machinery but also reduces their performance. To overcome this problem, thermal spray technology has been a recurrent choice among other surface coating techniques to obtain adequate mechanical and tribological properties.[1] Mainly because of their usability and high adhesion strength, flame spray (FS) and high-velocity oxygen fuel (HVOF) spraying techniques have been a common choice for coatings production.[2,3] The HVOF method provides undeniable advantages in obtaining cermet coatings such as tungsten carbide (WC), because of high-impact velocities and low spraying temperatures, producing coatings with low porosity, excellent adhesion to the substrate, and high resistance
MIGUEL REYES MOJENA, MARIO SA´NCHEZ OROZCO, and HIPO´LITO CARVAJAL FALS are with the College of Mechanical Engineering, Oriente University, Av. Las Ame´ricas s/n, Santiago de Cuba, CP 90900, Brazil. VALTAIR ANTONIO FERRARESI is with the College of Mechanical Engineering, Federal University of Uberlaˆndia, Campus Santa Moˆnica, Uberla˜ndia, MG 38400-902, Brazil. CARLOS ROBERTO CAMELLO LIMA is with the Production Engineering Graduate Program, Methodist University of Piracicaba, Rod Luis Ometto, Santa Ba´rbara d’Oeste, SP 13450900, Brazil. Contact e-mail: [email protected] Manuscript submitted October 7, 2016. METALLURGICAL AND MATERIALS TRANSACTIONS A
to wear.[4,5] Nevertheless, the FS method allows for obtaining coatings on internal surfaces such as internal diameters of pipes, pump housings, etc., areas usually inaccessible for HVOF technique.[2] Also, when using the flame spray technique with cored wire feedstock (called flexicords), here named FSFC, it is possible to obtain ceramic and metallic coatings with high quality, achieving thicknesses greater than with HVOF and at an expected lower cost.[2] Erosive wear resistance of the cermet coatings depends on different factors: the size and volume fraction of the reinforced phase, the amount, types of matrix materials, the shape and size of the erosive particles, and the aggressiveness of the environment.[6,7] The microhardness and fracture toughness of the matrix and reinforcement, as well as the reinforcement/matrix interfacial strength, are the most important mechanical factors determining the tribological properties of these coatings.[8] The material lost during erosion depends on the angle of incidence, impact velocity, and mass of the erosive particles. For ductile metals, material loss tends best to acute impact angles. Nonetheless, in the case of brittle materials, the material loss increases with the increasing angle of incidence of the particles, obtaining higher values of material loss at a 90 deg angle.[9,10] This mechanism also depends on the shape and material of erosive particles, among other factors.[11] To predict the erosion mechanism in different materials, in 1990, Sundararajan et al. proposed a parameter calle
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