Laser joining of Al2O3 liners with Al2O3-MgO-SiO2 glass-ceramic fillers

The influence of fillers composition on microstructure, the physical and chemical properties of joints is studied. Thermal mismatch between fillers and Al2O3 liners during laser joining process could be effectively reduced with the increase of MgO content. The mutual diffusion and the substitution reaction lead to the formation of the eutectic spinel phase (Mg, Fe)Al2O4. The interfacial atomic diffusion is enhanced by the addition of MgO. The joints corresponding to fillers composed of 70 wt.% Al2O3-15 wt.% MgO-15 wt.% SiO2 have the optimal mechanical performance. The average flexural strength of joints reaches 168 Mpa which is 80% of the Al2O3 liner (200Mpa). The weight loss of the joint interlayer in 10 wt.% HCl (pH = 0.45) for 24 h is 0.62 mg/cm(2) which is 0.16 mg/cm(2) lower than that of the liner. The softening temperature of joint interlayer exceeds 1500 degrees C. The reliability of Al2O3-lined joints could be maintained during the sequential process of arc welding for outer steel pipe layers. The corrosion of pipe layers could be effectively avoided.