金属添加剂对SHS陶瓷内衬复合管微观结构与界面连接的影响

Influences of metallic additive on microstructures and interface-bonding of ceramic-lined composite pipes fabricated by the SHS process

基于重力分离SHS法制备陶瓷内衬复合管,以(CrO3+Al)为燃烧体系,通过添加并调整(TiO2+Al+C)子体系与Ni金属添加剂之间的成分比例,合成出具有钢基体、中间过渡合金层与内衬陶瓷三层结构的复合管。研究金属添加剂Ni对燃烧行为、碳化物颗粒原位合成与分布、陶瓷/金属微连接及复合管力学性能的影响。研究发现,随着Ni添加量增多与(TiO2+Al+C)含量降低,反应体系的绝热燃烧温度与燃烧速率上升,Ni的添加与熔化促进反应中亚化学计量比的富Ti碳化物形成,同时也因液相传质促进该碳化物溶解于金属熔体中,并经结晶形成呈梯度分布于中间过渡合金层上的富Ti碳化物。经对复合管力学性能测试与SEM观察,发现添加适量的Ni粉,可以控制中间过渡合金层中碳化物的体积分数与分布,有利于内衬陶瓷层、中间过渡合金层与钢基体之间的连接,从而使复合管径向压溃强度与抗剪强度提高。

On the basis of using gravitational separation Self-propagation High-temperature Synthesis （SHS） process to produce ceramic-lined composite pipes, the composite pipes with three-layer structure （steel substrate, intermediate alloy and lined ceramics） were fabricated by adding （TiO2＋Al＋C） subsystem and Ni metallic additive into （CrO3＋Al） combustion system and adjusting composition proportion between two sides, and influences of Ni metallic additive on combustion behaviors, in-situ synthesis and distribution of carbide with Ti enrichment in the intermediate, micro-bonding between metal and ceramics as well as mechanical properties of the pipes were investigated. The experiment results indicate that with increasing weight fraction of Ni powder and reducing weight fraction of （TiO2 ＋ Al ＋ C） subsystem, adiabatic combustion temperature and combustion velocity of the whole system are increased, and adding and melting of Ni promotes substoichiometric carbides with Ti enrichment to be formed through mass transport in the liquid phase, meanwhile also promotes substoichiometric carbides with Ti enrichment to be remelted and dissolved in metallic melts, subsequently carbide with Ti enrichment are formed in the intermediate with grated distribution through crystallization. Mechanical test and SEM observation show that adding right amount of Ni powder will cause volume fraction and distribution of carbide in the intermediate to be controlled, and is advantageous to joining of ceramics, intermediate alloy and steel substrate, resulting in increasing of radial crushing strength and compressive shear strength of the composite pipes greatly.