Preparation of a modified multi-component phosphate adhesive for connection of 316L stainless steel and its reinforcement mechanism

In this paper, a novel phosphate-based adhesive with excellent high-temperature bonding strength was prepared by using phosphate as the matrix and modified B ₄C, modified TiO ₂ as well as low-temperature fused Zn–B–Si–Al-R glass materials as fillers. The effects of heat treatment temperature and filler compositions on the high-temperature bonding strength of the adhesive were investigated. The results indicated that the aluminum phosphate in the adhesive was transformed from orthorhombic to cubic crystalline at 210 ± 5 °C, which increased the cell stacking density from 2.19 g/cm ³ to 2.74 g/cm ³ and made the binder dense. After calcination at 500 °C, a large number of pyrophosphates were generated inside the adhesive, and the chemical bonds such as P–O–Si and P–O–Cu in these pyrophosphates formed reticulated skeletal macromolecules, which improved the network structure of the transition zone between the adhesive and stainless steel. Meanwhile, the difference in potential resulted in the exchange of Fe and Cu ²⁺, H ⁺ at the bonding interface to enhance the high-temperature resistance and bonding strength of the specimen. When the additions of La ₂O ₃, Fe ₂O ₃, ZrO ₂ , CuO were1.2%, 5%, 10%, and 15%, the maximum tensile strength of the specimen reached 8.73 MPa at 500 °C. The phosphate binder prepared in this work could be widely used in the field of high-temperature material repair such as aerospace and energy.