Effect of bond layers and vacuum annealing on sprayed NiCr-30%Cr₃C₂ metallic-ceramic coating properties

Abstract

NiCr-30%Cr3C2(mass fraction) ceramic-metallic coatings were sprayed with two types of bond layer (electro-deposited Ni+HVOF NiCr bond layer and electro-deposited Ni bond layer) by HVOF. The coating with Ni bond layer was vacuum annealed at different temperatures (800, 850℃ and 900℃). Phase, microstructure and mechanical properties under different loads of coatings were characterized by X-ray diffractometer (XRD), scanning electron microscope (SEM), electron-tensile tester, ball-on-disk (BOD) and step profiler. The results show that the adhesion strength of the coat-ing with Ni bond layer reaches 64MPa and is improved obviously after annealing. The wear resistance of the coating with Ni bond layer is superior to that with Ni-NiCr bond layer and improved signific-antly under 20N loading, while the wear resistance of the two coatings is with no much difference and the wear resistance of the coating with Ni bond layer is decreased after annealing under 5N loading.

Keywords

• HVOF spraying
• bond layer
• annealing treatment
• wear resistance
• adhesion strength