高温热腐蚀与蠕变疲劳耦合作用下镍基高温合金的损伤机理与寿命预测研究

The turbine blades in engines suffer severe operation conditions characterized by operation environment and mechanical stresses. The turbine blades in the marine environment suffer from serious material degradation at a significantly faster rate namely hot corrosion and under a fatigue load at the same time. Thus far, a few efforts have been made to investigate the effect of hot corrosion on the creep-fatigue properties of nickel-base superalloys. The existing mechanics analysis method and life prediction model cannot express the true nature of the damage mechanism and service life. The high-temperature hot corrosion damage mechanics and evolution law under creep-fatigue loading for the typical turbine blade materials was investigated. The damage estimation index of nickel-base superalloys subjected the hot corrosion and under a fatigue load simultaneously was proposed. And the evolution law of the superalloys damage was revealed. Based on diffusion theory and continuum damage mechanics theory, the damage constitutive model of creep-fatigue damage under effect of corrosive media will be established. Therefore, the coupling evolution process under the complex environments and complex load was numerically simulated. The life prediction under chemical and mechanical factors was completed, which provides important theoretical basis and scientific methods for structural strength design and life estimate of turbine blade.

航空发动机涡轮结构的真实工作状态处于环境与机械荷载的耦合作用。沿海地区及工业污染区服役的涡轮叶片结构受到热腐蚀与荷载的耦合作用，这种耦合作用加剧了叶片结构的损伤劣化。针对先进航空发动机涡轮叶片材料定向凝固镍基高温合金热腐蚀与蠕变疲劳耦合损伤行为的研究鲜有报道，已有的力学分析方法及寿命预测模型也未能真实反映材料的损伤演化行为及寿命强度。本项目研究典型涡轮叶片材料在蠕变疲劳载荷作用下高温热腐蚀损伤演化机理与规律；提出热腐蚀与蠕变疲劳载荷耦合作用下损伤评价指标，揭示热腐蚀与蠕变疲劳载荷耦合作用下材料损伤演化规律；基于扩散理论与连续损伤力学理论，建立在热腐蚀介质作用下的疲劳蠕变损伤的本构模型，数值模拟复杂环境与复杂载荷耦合作用下损伤演化过程，实现化学与力学因素协同作用下的材料与结构寿命预测，为涡轮叶片结构强度设计与寿命预估提供重要理论依据和科学方法。

本项目重点研究高温热腐蚀与蠕变疲劳耦合服役条件下涡轮叶片典型材料的损伤演化机理和规律以及寿命预测方法。经过三年的努力，项目组成员在机械载荷作用下热腐蚀损伤演化机理、损伤演化规律以及寿命预测方法等基础研究方面取得了一些创新性研究成果。试验研究了典型航空发动机涡轮叶片材料DZ125合金在循环载荷作用下的热腐蚀损伤演化机制，分别提出了无载荷以及循环载荷作用下的热腐蚀动力学模型；试验研究了蠕变保载时间对DZ125合金热腐蚀疲劳寿命的弱化规律，且在微细观上揭示了蠕变保载对热腐蚀疲劳寿命的损伤机理以及涂层的防护机理和规律；在工程力学框架下定义了热腐蚀损伤，提出了热腐蚀损伤及其与疲劳损伤的耦合形式；分别提出了基于线性累计损伤法则和断裂力学理论的两种热腐蚀疲劳寿命预测方法，并将寿命预测方法扩宽至磨损、氧化和磨损等表面损伤引起的疲劳寿命退化情况中。