A new approach of abrasive wear performance of flame sprayed NiCrSiBFeC/SiC composite coating

Abstract

The abrasive wear resistance of coatings of NiCrBSiFeC with the addition of 40% SiC applied by the flame spray process was evaluated. 420 μm thick layers were applied onto AISI 1020 steel substrates. The powder used is a commercial Metco ML16-C (Ni16Cr4Si4B3Cu3Mo2.5Fe0.5C) with particle size in the range of −125 + 53 μm and mechanically mixed for 2 h with medium-sized 29 μm SiC powder. The coatings were further remelted by the technique of surface flame melting. The surface and cross-sectional characterization, before and after the remelting, was performed by scanning electron microscopy (SEM), dispersive energy microanalysis (EDS), and x-ray diffraction (XRD). Microhardness profiles (HV0.05) were obtained in the cross-section. Abrasion tests were performed according to the ASTM G65 standard. It was found that the remelting process decreased the porosity, eliminated the defects of the interlayer as well as coating/substrate interfaces. The addition of the 40% SiC reinforcement caused an increase in the microhardness values mainly in the regions closer to the surface, on average 1119 HV0.05 in coatings without remelting and 1086 HV0.05 after remelting. The remelting decreased the mass loss, being 8.4 times less in the coatings without adding SiC and 6.8 times less in the coatings reinforced with SiC. NiCrBSi coatings reinforced with SiC and not remelted showed 17% less loss of mass. The quantitative analysis carried out by XRD enables us to confirm that the abrasive wear mainly causes significant loss of the eutectic phases (Ni3Si2 and Ni3B) and the detachment of the Cr carbides and borides. Further, the austenitic matrix (Ni γ) shows superior resistance to wear.