Microstructure evolution and fracture behavior of heat treated enamel coating: Experiment and finite element analysis

The enamel coating (CaO-BaO-MgO-SiO2-Al2O3) is prepared and performed isothermal oxidation at 900 degrees C. With the increase of oxidation time, the microstructure and phase evolution of enamel coating are analyzed. Meanwhile, the fracture toughness of heat treated enamel coatings are characterized using the micro-cantilever bending method. The experimental result indicates that the heat treatment can promote the precipitation of oval crystal particles from the enamel itself. With increase of crystallinity, the fracture toughness of heat treated enamel coatings increases from 2.35 to 4.20 MPa.m(1/2). In addition, finite element method (FEM) with inserting global cohesive elements is adopted to estimate the fracture of micro-cantilever for enamel including elliptical crystals. Both load-displacement curves and failure modes from FEM analyses agree well with those from experiments. Meanwhile, the fracture mechanisms including crack deflection, crack bridging, intergranular and transgranular fracture of the enamel can be revealed.