Composition optimization and properties of porcelain |fused to metal with functional gradient material structure

The porcelain-fused to metal (PFM) based on nickel-chromium alloy with the composition gradient structure was prepared by adding Ni，Cr，NiO and Cr₂O₃ in different proportions to the porcelain powder mainly constituted by leucite. The bending strength and thermal expansion coefficient (TEC) of the different gradient compositions were tested. SEM and XRD were also employed to characterize the as-prepared gradient samples. The thermal stress of the samples was simulated using  an elastic stress model. The results show that when m(NiO)∶m(Cr₂O₃)∶m(Ni)∶m(Cr)＝0∶50∶40∶10，the functional gradient material (FGM) with high bending strength（101.217 MPa）and comparatively low thermal stress is obtained. The thermal stress curves exhibit that FGM structure could relax the thermal stress of the samples in the cross-sectional direction. The study result also indicates that the smaller particle size of the porcelain powder could improve the performance of FGM and reduce the sintering temperature，and the bending strength of the gradient materials presents aeolotropism.