T. Varis, E. Turunen, VTT Technical Research Centre of Finland, Espoo, Finland; A. G. Valarezo, S. Sampath, S.U.N.Y at Stony Brook, Stony Brook, NY; X. Liu, Helsinki University of Technology, TKK, Espoo, Finland; S. P. Hannula, Helsinki University of Technology, Espoo, Finland
Despite the extensive applicability of HVOF WC-Co coatings , there are still many open questions of the effecting factors on the coating performance depending on the used spray system, spray conditions and powder quality. Toughness and wear resistance of the coating can vary significantly between different process conditions resulting in performance issues, such as cracking in grinding and changing wear resistance.
In this paper the formation of HVOF sprayed tungsten carbide coatings is studied in through an integrated strategy. First order maps are created by using online-diagnostics to assess particle states and droplet impact is characterized using single splat studies. Coating formation is also studied by performing in-situ measurements for stresses and residual stresses. Effect of substrate heating and peening effect is examined under different process conditions. The data generated from spray conditions and coating formation is analyzed through detailed microstructure analysis. Instrumented nanoindentation combined with AFM is used for evaluate the ultrafine microstructure in the submicron scale. Coating microstructure is studied by SEM, and phase structure by XRD. Coating properties such as hardness, wear resistance, elastic modulus and fracture toughness are discussed with a goal to establish linkage between properties and particle characteristics via second order process maps.
Summary: Despite the extensive applicability of HVOF WC-Co coatings , there are still many open questions of the effecting factors on the coating performance depending on the used spray system, spray conditions and powder quality. In this paper the formation of HVOF sprayed tungsten carbide coatings is studied in through an integrated strategy. First order maps are created and effect of in-situ stresses during spraying are studied together with the ultra microstructure in the submicron scale. Coating properties such as hardness, wear resistance, elastic modulus and fracture toughness are discussed with a goal to establish linkage between properties and particle characteristics via second order process maps.
