| Inconel 718 high-temperature alloy is widely used in aerospace applications to make components such as turbine blades,guide vanes,and combustion chambers that have high corrosion and oxidation resistance and can operate under high temperature and pressure conditions.However,these components are exposed to wear during the operating cycle,which can lead to component failure before their expected life due to tensile stress,fatigue,and micro-motion damage.And the conventional coatings prepared from soft metals and other lubricant materials can no longer meet the performance requirements of nickel-based high-temperature alloys in extremely harsh environments due to their low hardness,low strength,and poor wear resistance.Therefore,the preparation of self-lubricating composite coatings by laser melting technology is one of the easiest and most convenient methods to promote the green and low carbonization of industry,reduce the wear of workpieces and improve the wearing stability of components.The main objective of this paper is to prepare seven composite coatings with different contents,including pure Co powder,WC powder,and Cu powder with lubricating effect,on Inconel 718 high-temperature alloy using laser melting technique,with coatings of 100wt.%Co,5wt.%WC,10wt.%WC,15wt.%WC,5wt.%WC-5wt.%Cu,5wt.%WC-10wt.%Cu,and 5wt.%WC-15wt.%Cu to improve the wear resistance of the coatings.SEM,EDS,and XRD were used to study the organization and tribological properties.The results show that the main physical phases of composite coatings are:solid solution y-Co and FeNi,hard phase FexNby,Cr3C2,WC,and lubricant phase Cu.The microhardness of the seven composite coatings are:478.69 HV0.5,501.78HV0.5,548.81 HV0.5,586.70 HV0.5,483.82 HV0.5,and 483.82 HV0.5,461.74 HV0.5 and 448.65 HV0.5,all of which are more than 1.7 times that of the matrix(262.7 HV0.5).With a rise in WC content,the microhardness of the Co-WC composite coating rose;conversely,an increase in Cu content caused the microhardness of the Co-WC-Cu composite coating to fall.The main reason is that the addition of a hard phase to a hard material leads to an increase in the hardness of the composite and the addition of a soft phase leads to a decrease in the hardness of the composite.the tribological properties of the Co-WC-Cu composite coatings are both higher than those of Inconel 718 high-temperature alloy.Among the Co-WC composite coatings,the Co-5%WC composite coating exhibits superior friction reduction performance at both room temperature and high temperature,with friction coefficients of 0.566 and 0.445,respectively.Additionally,the Co-15%WC composite coating demonstrates the best wear resistance of 0.65 × 10-5 mm3/N·m at room temperature,while the Co-5%WC-5%Cu composite coating exhibits the best wear resistance of 4.50 × 10-5mm3/N·m at high temperature.The wear mechanisms can be described as follows:The 5%WC coating experiences predominantly abrasive and oxidation wear,the 15 wt.%WC composite coating experiences primarily adhesion and oxidation wear,and the Co-5%WC-5%Cu composite coating experiences plastic deformation,abrasive,and oxidation wear.In summary,the mechanical and tribological properties of Co-WC/Cu composite coatings are better than Inconel 718 high-temperature alloy,both at room temperature and high temperature,which can greatly reduce the loss of its surface and improve the service life.In this paper,the role of WC and Cu in the coating is discussed in depth to provide a theoretical basis for enriching the melt coating material system. |
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