Effect of nitrogen protective atmosphere on microstructure and high temperature erosion property of TiAl_3 and Cr_3C_2 composite coatings

Three kind of supersonic arc-spraying coatings containing TiAl3 and Cr3C2 intermetallics were fabricated with and without the protective atmosphere of nitrogen.The effect of nitrogen atmosphere on microstructure and high temperature erosion property of the coatings were studied by optical microscopy,microhardness testing,scanning electron microscopy(SEM) and energy dispersive spectra analysis.It was found that the oxides in the coatings reduced the interfacial strength between the neighboring splats which resulted from the arc-spraying procedure.Detachment,fracture,ploughing,and spalling of the splats were the main causes of high temperature erosion.Under the protective atmosphere of nitrogen,droplet oxidation was significantly reduced and density and structure homogeneity of the coatings improved,leading to remarkable increase of hardness.In the current investigation,the volume erosive rates of CCW1,CCW2 and CCW3 coatings arc-sprayed under N2 protective atmosphere decreased by 3.3,2.3 and 1.0 times as that under air atmosphere.