Examining Cu content contribution to changes in oxide layer formed on selective-laser-melted CoCrW alloys

In this study, CoCrW alloys with different Cu contents (0, 2, 3, and 6 wt%) were prepared by selective laser melting for dental applications. The bonding strength between porcelain and the metal in porcelain-fused-to-metal dental restorations could be considerably affected by the quality of Cr oxide formed on CoCr-based alloys. Recent studies revealed that the Cu element could affect the oxidation behavior of austenitic steels. Therefore, it is essential to investigate the effect of the Cu element introduction on the oxidation performance of CoCrW alloys. The SEM and SPM indicated that the Cu element considerably affected the microstructures and the roughness of the oxide layer. XRD analysis showed that the oxide layer in CoCrW alloys was mainly composed of Cr2O3 and CoCr2O4, while trace amounts of CuO and Cu2O were found after the addition of the Cu element. The depth profiles obtained by XPS suggested that the Cu content in the film structure could affect the thickness of the Cr oxide regions, which revealed that the addition of the Cu element accelerated the oxidation of CoCrW alloys by promoting the diffusion of the O element into the inner layer. The three-point bending test indicated that the addition of Cu had a negative effect on the bonding strength between porcelain and the metal substrate.