材料期刊网

以不同配比的Ni粉末和TiB2粉末混合物为预置层,利用激光原位技术在钛合金表面制备了bcc结构的NiTi合金、TiB短纤维与TiB2颗粒增强钛基复合涂层.运用XRD,SEM与EPMA等实验手段,对合成的钛基复合涂层进行测试分析.结果表明,随着激光功率密度与Ni粉末添加量的增加,涂层表面成型质量得到改善;然而随着Ni添加量的提高,涂层中出现了NiTi2新相,且TiB短纤维变得粗大;通过热力学计算可知,反应驱动力大小顺序为Ni3Ti＞NiTi2＞NiTi＞TiB,并结合涂层中相种类及含量的变化规律,探讨了不同元素反应间的竞争机制.

Laser cladding is a technique in which a laser beam is used as the heating source to melt the alloy powder to be clad on the surface of titanium alloy substrate.Currently,the surface of many titanium alloy components needs repairing after a period of service in order to extend their service life.TiB and TiB2 are considered as the excellent ceramic reinforced particle for their compatible physical and thermodynamic properties,high hardness and Young's modulus of elasticity.The intermetallic compound NiTi,well-known for its shape memory effect and pseudo-elasticity,is one of the rarely few intermetallic compounds having excellent combination of high strength,ductility and toughness as well as excellent wear resistance and fabrication processing properties.An insitu TiB/TiB2 structured ceramic materials as the reinforcing phase and NiTi intermetallic phase as the matrix would be expected to have an outstanding combination of high hardness and toughness.NiTi alloy,TiB short fiber and TiB2 particulate reinforced titanium matrix composite coatings were prepared by laser in situ synthesis on titanium surface with different ratios of Ni powder and TiB2 powder mixture as a preset level.Synthesis of titanium matrix composite coating was analyzed by XRD,SEM and EPMA.The results show that the surface quality of the coating increases with increasing laser power density and the amount of Ni powder.Whereas,the new phase of NiTi2 and coarse diameter of TiB short fiber are found in the coating when the amount of Ni added is improved.The reaction mechanism is discussed based on thermodynamic calculations.The reaction driving force size to Ni3Ti＞NiTi2＞NiTi＞TiB order arrangement are found by thermodynamic calculation,and reaction meehanism of competition between the different elements is discussed based on phase variation of the type and content in the coating.