时效热处理对紫铜表面钴-镍复合涂层组织与性能的影响OA

Tuyere is a core component within the ironmaking blast furnace(made of copper),and its function is to deliver hot air and inject pulverized coal into the blast furnace.Due to the low hardness and poor wear resistance of copper,the tuyere is prone to damage in harsh environments.Utilizing cladding technology to construct a wear-resistant protective coating on copper surface is an important way to extend its service life.Existing research has confirmed that cobalt-based alloy coatings can significantly improve the short-term service performance of copper,and a nickel-based transition layer serves as a bridge for achieving metallurgical bonding between the cobalt-based alloy and the copper substrate.However,the long-term service stability of Co-Ni composite coatings remains a research gap.Considering that aging heat treatment can simulate the conditions of long-term high-temperature service for coatings,this work utilizes this method to explore the high-temperature stability of plasma cladded Co-Ni composite coatings,aiming to verify whether they meet the application requirements of blast furnace tuyere. Based on the Co06/Ni60A composite coating prepared on a copper surface by plasma cladding in the early stage and the actual service environment of blast furnace tuyere,the coating was subjected to aging heat treatment at 500℃in argon gas for 0 h,20 h,100 h,and 500 h,respectively.Subsequently,microstructural characterization and performance testing were conducted.The microstructure and chemical composition of coating were analyzed by scanning electron microscopy(SEM)and energy dispersive spectroscopy(EDS).The phase composition changes of coating were identified with an X-ray diffractometer(XRD).The microhardness of the coating was measured with a microhardness tester.The wear resistance evolution of the coating was tested with a friction and wear tester. After heat treatment for 20 h,the metastable Cr7C3 phase in the Co-based surface layer partially transformed into Cr23C6,accompanied by the precipitation of white carbides M6C(rich in Cr,Co,Ni,W).The grain size of the γ-Co solid solution and the Cr23C6 phase exhibited a tendency to increase.The Ni-based transition layer did not undergo phase transformation,but there was also a coarsening phenomenon in the solid solution grains and reinforcement phases.The degree of interfacial diffusion between the surface layer-transition layer and the transition layer-copper substrate increased,promoting metallurgical bonding.After heat treatment for more than 100 h,the microstructure of the coating basically stabilized.Due to microstructural coarsening and phase transformation,the average hardness of the entire coating decreased from 502.5HV(0 h)to 447.1HV(500 h),and the decreasing gradient gradually slowed down.The wear resistance also showed a trend of decreasing first and then stabilizing,with an overall small decrease.After heat treatment for 500 h,it was only reduced by 1.65 times compared with that before heat treatment,and the wear mechanism shifted from single abrasive wear to a combination of abrasive wear and adhesive wear.In summary,although the performance of the Co-Ni composite coating on a copper surface degrades to some extent after long-term high-temperature service,it ultimately remains stable and can generally meet the application requirements of the blast furnace tuyere.