Bonding properties of plasma sprayed Cr₃C₂-NiCr and NiAl/Cr₃C₂-NiCr coatings on CuCrZr alloy surface

The Cr₃C₂-NiCr,NiAl/Cr₃C₂-NiCr coatings were prepared by plasma spraying on the CuCrZr alloy.The bonding strength between the coating and the substrate and the thermal shock resistance were tested.The change of the phases and the coating bonding mechanism were investigated by means of SEM,EDS,XRD.The results show all coatings have good bonding strength.During the process of spraying the NiAl coating,an exothermic reaction generates between Ni and Al,and three kinds of intermetallics(Al₄Ni₃,Al₃Ni₂,AlNi₃) are formed.The remaining Al can react with Cu substrate to form Cu₃Al₂,CuAl₂ and CuAl,hence,the micro-metallurgical bond exists in some micro-zones.However,the bond type is mainly mechanical bond for all coatings.The bonding strength depends on the mechanical properties of the coating material,under the conditions of the same substrate and appropriate parameters.The thermal shock resistance of NiAl/Cr₃C₂-NiCr coating is better than that of Cr₃C₂-NiCr coating.