This work designs a silica (SiO₂) layer on a molybdenum metal core to provide new insights on the corrosion resistance of the silica/silicide coating in the Ni-based superalloy. The molybdenum substrate coated with MoSi₂ by pack cementation was pre-oxidized to fabricate a cristobalite scale on the surface and the preoxidation specimens were chosen to examine the corrosion-resistant property by using a DSM11 superalloy at 1550 °C. In order to prepare a cristobalite layer, the microstructure evolution of a 40- µm MoSi₂ coating with the different oxidation parameters (temperature and time) was investigated. After casting test, the different casting results showed that the silicide layer was dissolved in the molten superalloy. However, the molybdenum matrix was found to be protected by the cristobalite layer, as well as accompanied by the cristobalite layer partially destroyed at the core/superalloy interfaces. Furthermore, the reason for the destruction of cristobalite layer was analyzed. The failure mechanism of the cristobalite layer was proposed during the cast process.

In this study, a modified Curie–Weiss model was established for the magnetic susceptibility of high-purity molybdenum and Mo–La alloy powders. The elemental composition was analyzed by GDMS, and combined with the M–T and M–H data measured by SQUID, the temperature-independent contributions of weakly magnetic elements such as La and the paramagnetic contributions of impurity ions such as Fe, Co, and Ni were distinguished. Based on the parameters obtained from the nonlinear least squares fitting, the deviation between the magnetic susceptibility at room temperature calculated by the model and the experimental value was within 5%. The results show that this model can reasonably describe the influence of trace impurities on the magnetic susceptibility of the system and provides an effective method for the magnetic prediction of high-purity metal powders.