TiAl-Nb金属间化合物涂层-基体界面在液锌磨损-腐蚀耦合作用下的演变规律及其对腐蚀磨损行为的影响机制

The corrosive wear of key equipments in hot dip galvanizing, such as sink roll system, is serious and this problem of short service life needs to be solved urgently. It was found by our research group in the early stages that TiAl-Nb intermetallic possesses an excellent corrosive wear resistance. Unfortunately, it is too hard to use to sink roll as a bulk material because of inadequate room-temperature ductility. On the basis of preliminary explorations for thermal spraying types, sand blasting pretreatment, spraying parameters, and bond coat sorts, we have pointed out the new idea that the obtainment of the double-layer-structural TiAl-Nb/NiCrAl coating with high interfacial bonding strength and high density on 316L substrate being normally served in actual sink roll now by supersonic spraying is a good way to solve the above mentioned problem. It is of crucial importance for a novel type of corrosive wear resistant materials in liquid zinc to figure out corrosive wear mechanism..The corrosive wear behavior of TiAl-Nb/NiCrAl coating in liquid zinc, the interface microstructures such as composition distribution and the nano-scaled 3-dimentional element distribution, the micro-mechanical characteristics by nano-probe of the coating-substrate interface, and their evolution behaviors under the interaction of wear and corrosion in liquid zinc will be investigated respectively in this program by means of the self-made liquid zinc wear-corrosion testing device which can simulate the actual working conditions combined with the advanced characterization techniques of microstructures. The interface evolution rules and their influence mechanism to corrosion wear behaviors will be revealed from the microscopic level. Finally, the interaction rules of wear and corrosion & the micro-mechanisms of corrosion wear of TiAl-Nb/NiCrAl coating will be discovered. It is of academic value for the further optimization design and preparation of TiAl-Nb intermetallic coating and the enrichment of liquid metal corrosion wear theory.

热镀锌关键设备沉没辊腐蚀磨损严重，寿命短，亟待解决。本课题组前期发现TiAl-Nb具有超强液锌腐蚀磨损抗力，但由于室温塑性不足，作为整体材料难以在沉没辊上使用。在对热喷涂种类、喷砂预处理、喷涂参数和打底层探索的基础上，我们提出了在现实际使用的316L基体上用超音速喷涂制备高界面结合强度、高致密度、双层结构TiAl-Nb/NiCrAl涂层这一新思路。弄清腐蚀磨损机制对于一种新型耐液锌腐蚀磨损材料至关重要。.本项目拟在自制的模拟实际工况的腐蚀磨损装置上，结合组织结构先进表征方法，研究涂层的腐蚀磨损行为，界面成分分布、纳米尺度界面元素三维分布等精细微结构与纳米力学探针微观力学特征，及在液锌磨损-腐蚀耦合作用下的演变行为。从基础层次揭示界面演变规律；及其对腐蚀磨损行为的影响机制；阐明涂层的磨损-腐蚀交互作用规律与腐蚀磨损微观机制，对涂层进一步优化设计与制备、丰富液态金属腐蚀磨损理论具有学术价值。

热镀锌关键设备沉没辊腐蚀磨损严重，寿命短，亟待解决。本项目系统研究了喷砂工艺参数、热喷涂工艺、喷涂工艺参数、粘结层材料、顶层成分、喷涂粉末制备方法与涂层梯度结构对316L基体粗糙度/形貌、涂层组织结构与性能的影响规律，优化获得了TiAl-Nb涂层制备最佳工艺；研究了涂层精细显微结构特征与热震行为，涂层主要由γ、θ和α2组成，为典型超音速喷涂涂层层状结构，结合紧密，无裂纹和孔洞，组织均匀，孔隙率小于0.86%，结合强度高达66MPa。从介观尺度看，涂层界面为机械结合，从纳米尺度看，顶层/粘结层与粘结层/基体界面均有100nm反应层，成分发生逐渐过渡，界面从纳米尺度上为冶金结合，顶层/粘结层界面反应层为非晶，而粘结层/基体界面反应层为Fe3Ni，与基体和粘结层均存在取向关系：(11-1)γ-Fe//(1-11)FeNi3，[101]γ-Fe//[-1-10]FeNi3；(1-11)FeNi3//(111)γ-Ni，[-1-10]FeNi3//[0-11]γ-Ni，错配度分别为1.2%和1.1%。界面处纳米硬度及弹性模量变化不明显。涂层热循环41次开始开裂，81次20%区域脱落，开裂首先从顶层表面形成垂直裂纹、接着在顶层与粘结层界面处形成水平裂纹开始。.研究了静态腐蚀、冲蚀腐蚀、高温磨损、腐蚀磨损行为。静态和冲蚀腐蚀特征都为孕育型腐蚀，分为孕育期和快速腐蚀期，腐蚀寿命主要取决于孕育期。孕育期内涂层与液锌不润湿、不腐蚀；一旦进入快速腐蚀期，液锌与涂层发生扩散反应，形成腐蚀产物TiZn3，随后溶解到液锌中，由反应扩散和溶解机制控制。梯度涂层腐蚀寿命比双层涂层提高24%。冲蚀腐蚀寿命(53天)比静态腐蚀提高29%，其原因在于冲蚀效应导致涂层与液锌更难接触、更难润湿。高温磨损形貌呈现微裂纹、犁沟、疲劳坑与磨屑，由磨粒磨损和疲劳磨损共同作用。随载荷与速度增大，损失量提高。.腐蚀磨损形貌呈现微裂纹、犁沟与疲劳坑，腐蚀磨损过程以磨损为主，由磨粒磨损和疲劳磨损共同作用。随载荷与速度增大，损失量提高。由于孕育期的存在，冲蚀损失率始终为0，高温磨损损失率和腐蚀磨损损失率随时间、载荷与冲蚀速度增加而增大，腐蚀磨损损失率始终高于高温磨损损失率，腐蚀-磨损交互损失率随时间呈抛物线分布，随载荷与冲蚀速度均呈线性分布。这些研究结果为耐液锌腐蚀磨损材料的进一步研发、丰富液态金属腐蚀磨损理论具有重要意义。