【作者】 张贺；

【导师】 卞宏友； 宋文清；

【作者基本信息】 沈阳工业大学 ， 机械， 2025， 硕士

【摘要】 K465镍基高温合金因其优异的高温强度和抗蠕变性能,广泛应用于航空航天、燃气轮机等热端核心部件。在服役工况下,K465合金易出现裂纹和摩擦损伤等问题,激光沉积修复技术凭借能量调控精准、稀释率低等优势,可有效修复损伤零部件并延长其使用寿命。针对异质合金损伤修复,开展GH4169合金激光沉积修复K465合金组织与性能研究,探究沉积态、基体预热态及时效处理态试样的显微组织演化规律,并结合显微硬度和摩擦磨损性能测试,阐明组织与性能的关联关系。主要研究内容及结论如下:针对激光沉积修复过程中易产生沉积缺陷,影响成形质量等问题,开展GH4169合金激光沉积修复K465合金工艺参数优化与组织性能研究,优化了激光沉积修复工艺参数。结果表明:修复区顶部为等轴晶,中部及底部以柱状晶为主,枝晶间存在大量Laves相;相较于基体,热影响区中存在M₂₃C₆碳化物,同时γ′相数量增加;结合区处Fe、Cr、Co、Nb元素扩散,导致元素重新结合形成γ相、Laves相及MC碳化物多相结构。修复区显微硬度为356HV_0.3相较于基体显微硬度401HV_0.3,降低11.2%,摩擦系数较基体0.66提高至0.88,提升33.3%。针对激光沉积修复过程中温度梯度较大容易产生热应力裂纹等问题,在基体预热条件下进行K465合金激光沉积修复,探究基体预热对裂纹、组织及性能的影响。结果表明:预热可以降低温度梯度和冷却速率,减小结合区应力,有效抑制裂纹;修复区中部柱状晶向等轴晶转变,枝晶间Laves相呈现粗化形貌;预热温度导致结合区两侧元素浓度梯度减小,元素扩散强度减弱。预热300℃时,修复区显微硬度提升至396HV_0.3,较沉积态显微硬度提高11.2%,摩擦系数降至0.75。针对激光沉积修复过程中合金组织不稳定、性能弱化等问题,开展不同温度时效热处理试验,探究时效温度对组织、显微硬度及摩擦磨损性能的影响。结果表明:热处理后,高温促使修复区组织晶界重组,晶粒细化,链状Laves相转变为粒状结构,同时γ′和γ′′强化相析出;基体及热影响区中碳化物和强化相数量增加;结合区元素扩散明显,形成典型γ相、γ′相与MC碳化物多相耦合结构。时效720℃时,修复区显微硬度达464HV_0.3,较沉积态显微硬度提高30.3%,平均摩擦系数降至0.54。因此,相较于沉积态及预热态,时效720℃热处理态试样,综合性能最优。更多还原

【Abstract】 K465 nickel-based superalloy is widely used in aerospace,gas turbines and other hot-end core components due to its excellent high-temperature strength and creep resistance.Under service conditions,K465 alloy is prone to cracks and friction damage,and laser deposition repair technology can effectively repair damaged parts and prolong their service life with the advantages of accurate energy control and low dilution rate.In order to repair the damage of heterogeneous alloys,the microstructure and properties of K465 alloy were studied by laser deposition of GH4169 alloy,and the microstructure evolution of the samples in the sedimentary state,the preheated state of the matrix and the time-treated state was explored,and the correlation between the microstructure and the properties was clarified by combining the microhardness and friction and wear performance tests.The main research contents and conclusions are as follows:In order to solve the problems of deposition defects and affecting the forming quality in the process of laser deposition repair,the optimization of process parameters and microstructure properties of GH4169 alloy laser deposition repair K465 alloy was carried out,and the process parameters of laser deposition repair were optimized.The results show that the top of the repair area is equiaxed,the middle and bottom are mainly columnar crystals,and there are a large number of Laves phases between the dendrites.Compared with the matrix,M₂₃C₆carbides were present in the heat-affected zone,and the number ofγ′phases increased.The diffusion of Fe,Cr,Co and Nb elements in the binding zone leads to the recombination of the elements to formγphase,Laves phase and MC carbide multiphase structure.The microhardness of the repair area was 356HV_0.3,which was 11.2%lower than that of the matrix 401HV_0.3,and the friction coefficient was increased by 33.3%compared with the matrix 0.66 to 0.88.In order to solve the problems of large temperature gradient and easy to produce thermal stress cracks in the process of laser deposition,the laser deposition repair of K465 alloy was carried out under the condition of matrix preheating,and the influence of matrix preheating on cracks,microstructure and properties was explored.The results show that preheating can reduce the temperature gradient and cooling rate,reduce the stress in the bonding zone,and effectively inhibit cracks.The columnar crystals in the middle of the restoration area changed to equiaxed crystals,and the Laves facies between the dendrites showed a coarsening morphology.The preheating temperature leads to a decrease in the element concentration gradient on both sides of the binding zone,and a decrease in the element diffusion intensity.When preheating at300°C,the microhardness of the repair area increased to 396HV_0.3,which was 11.2%higher than that of the sedimentary state,and the friction coefficient decreased to 0.75.In order to solve the problems of unstable microstructure and weakened performance of alloy in the process of laser deposition repair,aging heat treatment tests at different temperatures were carried out to explore the effects of aging temperature on microstructure,microhardness and friction and wear properties.The results showed that after heat treatment,the high temperature promoted the reorganization of the grain boundaries of the repair area,the grain refinement,the transformation of the chain Laves phase into a granular structure,and the precipitation ofγ′andγ′′strengthening phases.The number of carbides and strengthening phases in the matrix and heat-affected zone increased.The element diffusion in the binding zone is obvious,and a typical multiphase coupling structure ofγphase,γ′phase and MC carbide is formed.When the aging is 720°C,the microhardness of the repaired area reaches464HV_0.3,which is 30.3%higher than that of the sedimentary microhardness,and the average friction coefficient is reduced to 0.54,and the comprehensive performance is the best.Therefore,compared with the sedimentary state and the preheated state,the 720°C heat-treated specimen has the best comprehensive performance.更多还原