Adhesion at cerium doped metal-ceramic α-Fe/WC interface:A first-principles calculation

Electronic structure, stability and bonding strength of a-Fe/WC interfaces between Ce-doped and undoped WC cermet coating were investigated by first-principles methodology based on densityfunctional theory(DFT). Based on the minimum mismatched lattices, the relatively stable interface that forms between WC(100) and bcc a-Fe(100) was employed to predict the atomic structure, bonding,and ideal work of adhesion. There are three possible positions which were defined as OT, MT, HCP, taking into account both C-and W-terminations. The sequence of structural stability tested in this paper was:MT > OT > HCP. After full relaxation, the results show that only the first and second layers of the interface have significant influence on the electronic structure between Fe and WC. The interaction of Ce elements at the interface is achieved by comparing the interface structure and electronic structure of the doped and undoped interfaces. Ce doped interface possesses a shorter interface distance(d0 = 0.09776 nm)and a larger interface energy(Wad = 8.98 J/m2) than undoped interface(Wad = 8.76 J/m2,d0= 0.10134 nm).Charge density distribution and difference, and density of states were utilized to characterize the electronic properties and determine the interfacial bonding.The results demonstrate that strong covalent bonding existed in the undoped interface, while a mixed covalent/ionic bonding was formed at the Ce-doped interface.

Elevated temperature wear behaviour of CeO_2 modified WC-12Co coating

With the service environment becoming more and more severe, WC-Co coatings are required to apply in high temperature wear condition. In the present study, the sliding wear tests of CeO_2 modified WC-12 Co coatings were conducted at temperature of 450, 550 and 650 ℃. The wear loss and friction coefficient were recorded. The morphologies of wear tracks were observed every 1 h to investigate the dynamic wear mechanisms. The results show that the volume wear loss decreases with temperature increasing.The lowest volume wear loss is obtained at the temperature of 650 ℃ due to oxide films generated in the process of wearing. The wear mechanism is different at the temperature of 450, 550 and 650 0 C. Micro cutting wear, abrasive wear and oxidation wear dominate the wear mechanism at 450, 550 and 650 ℃,respectively. Abrasive wear and oxidation wear are the wear mechanisms at various temperatures.