The Influence Of Metallic Additives And Heat Treatment On Microstructure And Properties Of Ceramic-lined Pipes

The ceramic-lined pipes made by Centrifugal-SHS, for its high quality of resistance tocorrosion, heat and wear and excellent property of thermal insulation have the broadapplication prospect in many Industry sectors. But its own problems, such as poor interfacialbonding, low compactness and so on, severely limit its application fields. To solve theseproblems, this paper by adding Ni metallic additive and (TiO2+Al+C) subsystem into(Fe2O3+Al) combustion system and adjusting composition proportion between two sides tofabricate the composite pipes with three-layer structure (steel substrate, intermedi-ate alloyand lined ceramics) and study the influences of Ni metallic additive on in-situ synthesis anddistribution of carbide with Ti enrichment in the intermediate, Interface bonding betweenmetal and ceramics as well as mechanical properties of the pipes were investigated.Known from the analysis of XRD, the ceramic layer consists of main crystal phase Al2O3and substoichiometric carbides with Ti enrichment, Al2O3form the branch-crystal frameworkin the direction of radial, and substoichiometric carbides with Ti enrichment fills up the innerof the Al2O3branch-crystal; According to the SEM and EDS analysis draw that adding and Nipromotes metastable carbides with Ti enrichment to be formed through mass transport in theliquid phase, meanwhile also promotes metastable carbides with Ti enrichment to be remeltedand dissolved in metallic melts, metastable carbide with Ti enrichment are formed in the metallayer and ceramic layer with uniform distribution through crystallization. This reduces thedifferences of physical properties between ceramic layers and metal transition layer andimproves the situation of interface bonding and achieves a smooth transition; By hardness testand thermal shock test, the bending strength test method to test out the ceramic lining layerhas good resistance to bending and thermal shock performance. Subsequently carbide with Tienrichment distributed in the intermediate metal layers to promote disparty of hdrdnessbetween the ceramic layers and metal layer transition.At the same time, also studies the influence of different heat treatment temperature onthe organization, crack repaired and mechanical properties of ceramic-lined layer.Experiment results show that carbides with Ti enrichmenduring be oxidated to TiO2during the process of heat treatment and the ceramic layer consists of main crystal phase Al2O3andTiO2and CaTiO3phase, meanwhile TiO2fills up the inner of the Al2O3branch-crystal; Afterheat treatment, the density and bending resistance of ceramic-lined layer are improved,especially the density changes in significantly, the main reason is that TiO2(oxidation productof metastable carbides with Ti enrichment) occurs migration in pores and cracks, fills thedefect, improves the density of the ceramic-lined layer, also makes the bending resistancestrengthen.