Strengthening Mechanism of Al2O3 Ceramic-Lined Composite Steel Pipe Prepared by the SHS Gravitational Separation Process

Abstract

The Al2O3ceramic-lined composite steel pipes were produced by the SHS gravitational separation process (SHS-GS process) from Al, Fe2O3and Cr2O3as the raw materials within different reaction systems. The phase, composition, micro-structure and properties of ceramic coatings were investigated to discuss the strengthening mechanism of the composite steel pipe. The results showed that the phase composition of Al-Fe2O3-Cr2O3reaction system could be Al2O3and Fe-Cr alloy compared with the Al2O3-Fe-FeAl2O4phases of Al-Fe2O3reaction system, which led to the increase of strength and hardness of ceramic coating. Because the Fe-Cr alloy was formed instead of Fe element, and the addition of Cr2O3reduced the production of erodible FeAl2O4. The transition structure consisted of ceramic coating-transition layer-steel pipe was formed, and in its direction the Al and O element contents decreased, the metallic Fe and Cr increased. Therefore, the transitional changes of all the element contents could decrease the stress difference between the layers, and increase the bonding strength of the composite steel pipe.