面向焊接应力调控的Ti(C,N)基金属陶瓷表面梯度层的构建与界面反应机理

The brazing of Ti(C,N)-based cermet with steel will be favorite to its wide range of applications in industry due to the solution of toughness lacking and resource consuming. The high residual stress is the key problem to solve during the brazing of cermet with steel. The adjustment of filler including compositions and structures has been playing an important role in the stress relief in the present researches. Based on the fact that high residual stress appears on the cermet side of the joint, the project proposes that the research object transfer from the filler to the cermet matrix, and the cermet/filler interface continuity is improved by constructing a controllable and continuous graded layer being rich in metal phase and poor in ceramic phase on the surface of Ti(C,N)-based cermet which is formed by controlling C-activity of in sintering underthe decarbonization atmosphere, and the macro and micro residual stress can be alleviated by the interface continuity enhancement. In the project, the formation and controlling mechanism of graded layer on the surface of Ti(C,N)-based cermet under the decarburization atmosphere is researched, and a controllable gradient structure on the surface of cermets is constructed; the mechanism of metallurgical reaction at the interface of graded layer/filler/steel is investigated, the effect of surface gradient on the residual stress is revealed，and then the principle and interface reaction mechanism of the surface gradient layer of cermet are established for controlling welding stress. The project will expand the research on the residual stress and lay solid foundation for the alleviation of residual stress of Ti(C,N)-based cermet/steel brazing joint, thus it possesses scientific and engineering importance.

Ti(C,N)基金属陶瓷具有多种优异的性能，与钢焊接可解决其强韧性不足和资源过度消耗的问题，并有利于扩大其应用范围。残余应力是金属陶瓷/钢钎焊面临的关键问题，目前应力缓解主要针对工艺参数优化及钎料成分与结构调整。本申请针对高残余应力出现在接头金属陶瓷侧的特点，提出将缓解残余应力的研究重点从钎料转移到金属陶瓷基体，通过在脱碳气氛下控制金属陶瓷烧结体系中的C活度，在其表面构建可控的连续富金属相梯度层，实现金属陶瓷/钎料界面的连续化以调控接头残余应力。项目将明确Ti(C,N)基金属陶瓷在脱碳气氛下的表面富金属相梯度层形成与控制机制，揭示金属陶瓷表面梯度层/钎料/钢界面的冶金反应机理，探明金属陶瓷表面梯度化对钎焊残余应力的影响规律，进而建立面向焊接应力调控的金属陶瓷表面梯度层的构建原则与焊接界面反应控制机制。本研究为金属陶瓷/钢钎焊残余应力的缓解提供理论支撑，具有重要的科学与工程价值。

Ti(C,N)基金属陶瓷具有多种优异的性能，与钢焊接可解决其强韧性不足和资源过度消耗的问题，并有利于扩大其应用范围。残余应力是金属陶瓷/钢钎焊面临的关键问题。本项目针对高残余应力出现在接头金属陶瓷侧的特点，通过在金属陶瓷表面构建富金属相梯度层，实现了金属陶瓷/钎料界面的连续化以调控接头残余应力。本项目研究了脱碳气氛下Ti(C,N)基金属陶瓷的烧结微观组织演化、元素扩散与粘接相的体积流动机理，脱碳烧结工艺对金属陶瓷表面梯度层成分和结构的影响；研究了金属陶瓷表面富金属相梯度层内的金属相的成分、固溶特性以及相界面原子结构，分析了梯度Ti(C,N)基金属陶瓷的断裂特性，构建了梯度金属陶瓷的断裂模型；基于梯度Ti(C,N)基金属陶瓷在烧结过程中的应力特征与变形情况对梯度金属陶瓷的结构进行了优化，制备了多种梯度结构的Ti(C,N)基金属陶瓷材料；研究了Ti(C,N)基金属陶瓷/不锈钢的钎焊行为，梯度金属陶瓷/钢的钎焊界面反应与接头形成机理，实现了金属陶瓷/钢接头焊接应力的调控。本项目建立了脱碳烧结工艺与材料梯度层显微结构、成分分布、物性参数之间关系，实现了在金属陶瓷表面构建成分和厚度可控的梯度层结构，为制备高性能金属陶瓷材料以及构筑金属陶瓷复杂功能梯度结构提供了理论基础和科学依据；明确了Ti(C,N)基金属陶瓷梯度层/钎料/钢接头形成机理，为金属陶瓷/钢异种材料钎焊界面结构设计与应力调控提供了依据；揭示了表面梯度层对Ti(C,N)基金属陶瓷/钢钎焊接头应力状态和分布规律的影响，建立了梯度层宏微观结构、成分分布与接头微观组织结构、应力状态、性能之间联系，确立了面向焊接应力调控的金属陶瓷表面梯度结构的设计原则。