EFFECT OF Na₂B₄O₇ ADDITION ON THE STRUCTURE AND PROPERTIES OF Al₂O₃ CERAMIC-LINED STEEL PIPE PREPARED BY THE GS-SHS METHOD

By adding Na 2 B 4 O 7 into the Al-Fe 2 O 3 -Cr 2 O 3 reaction system, the Al 2 O 3 ceramic-lined steel pipe was prepared with the gravitational separation SHS method, and the influence of the Na 2 B 4 O 7 addition on the structure and properties of the produced composite steel pipe was investigated. The obtained results showed that the phase composition of the ceramic coating was Al 2 O 3 -FeCr Alloy-(Al 0.9 Cr 0.1 ) 2 O 3 composite, and with the increase of the amount of Na 2 B 4 O 7 addition, the Fe-Cr alloy particles left in the ceramic coating increased and distributed uniformly, and the denser ceramic coating was obtained. However, when the amount of Na 2 B 4 O 7 addition increased further to over 4 %, the ceramic coating became fractures, the hardness of ceramic coating decreased. The transition structure of steel pipe-transition layer-ceramic coating was formed, the thickness of the transition layer decreased with the addition of Na 2 B 4 O 7 , and the boundaries between the transition layer and the ceramic layer were less obvious, which would have a significant effect on the improvement of the bonding quality of the composite steel pipe.