【作者】 王震；

【导师】 郭鹏飞； 朱元胜；

【作者基本信息】 青岛理工大学 ， 机械（专业学位）， 2025， 硕士

【摘要】 Inconel 718合金以其优异的耐高温、耐腐蚀和抗氧化性能,而被广泛应用于航空发动机中。在Inconel 718合金粉末中添加纳米TiC陶瓷颗粒并利用激光粉末床熔融技术进行关键构件制备,是实现发动机减重并提高发动机服役效能的重要思路。然而,现阶段关于激光粉末床熔融TiC/Inconel 718复合材料的报道中,所添加纳米TiC颗粒质量分数多在2%以下,对于高TiC含量的镍基复材组织与性能等方面缺乏系统而全面的研究;此外,沉积态试样热处理后的显微组织演变与析出相行为仍需深入研究。基于此,本研究以添加纳米TiC质量分数分别为1.5%、3%的TiC/Inconel 718镍基复合材料为研究对象,进行激光粉末床熔融实验,并对沉积试样进行热处理,研究其微观组织演化规律及强化机理。建立了TiC/Inconel 718复合材料的工艺—组织—力学性能关系,明晰了不同强化机制对Inconel 718合金屈服强度提升的贡献值。为激光粉末床熔融纳米TiC添加的Inconel 718合金显微组织调控、性能提升提供理论支撑。本研究取得主要结论如下:(1)沉积态TiC/Inconel718复合材料中,晶粒以外延生长的柱状晶为主,TiC颗粒均匀、弥散地分布在Inconel 718基体中。TiC颗粒细化了 TiC/Inconel 718复合材料的显微组织,平均晶粒尺寸从9.56 μm降低至8.43 μm。随着TiC含量的增加,TiC/Inconel 718复合材料熔池内局部微观组织差异进一步减小。TiC/Inconel 718复合材料熔合线曲率半径的增大进一步诱导了枝晶的外延生长,使其最大织构强度由4.27上升到12.76。(2)相较于沉积态Inconel 718合金,沉积态TiC/Inconel718复合材料的强度明显提升,其中沉积态1.5 wt.%TiC/Inconel 718复合材料提升效果最为明显,抗拉强度、屈服强度分别提高了 121.7MPa、116.7MPa。这与纳米TiC颗粒阻碍位错运动及承载部分载荷有关。而在变形过程中,TiC颗粒脱粘后形成的凹坑成为裂纹源和裂纹扩展的通道,使复合材料的延伸率下降。(3)经过热处理后,Inconel 718合金的晶界处析出MC相,而TiC/Inconel 718复合材料晶界处析出MC/M23C6相,且MC/M23C6析出相数量随TiC含量的提高而增加。热处理态Inconel 718合金发生完全再结晶,晶粒结构主要由等轴晶组成,而热处理态TiC/Inconel 718复合材料其晶粒结构仍为柱状晶。(4)经热处理后的TiC/Inconel 718复合材料由于TiC颗粒和γ"相、γ’相的协同强化,力学性能提升显著。相比于热处理态Inconel 718合金,在室温拉伸时热处理态1.5wt.%TiC/Inconel718复合材料力学性能提升最明显,其屈服强度、抗拉强度分别提升120.2MPa、83.5 MPa,在高温拉伸时热处理态3wt.%TiC/Inconel 718复合材料力学性能提升最明显,其屈服强度、抗拉强度最高分别提升182.2 MPa、162.3 MPa,但两种复合材料的延伸率均有不同程度下降。(5)在室温拉伸中,晶界处MC/M23C6相破裂引发裂纹萌生与扩展导致了热处理态TiC/Inconel 718复合材料的失效。而在高温拉伸中,TiC/Inconel718复合材料则受晶粒尺寸不均匀和晶界处MC/M23C6相大面积脱粘的共同影响,使得TiC/Inconel 718复合材料在高温拉伸时失效。更多还原

【Abstract】 Inconel 718 alloy is widely used in aero-engines due to its excellent high temperature resistance,corrosion resistance and oxidation resistance.Adding nano-TiC ceramic particles to Inconel 718 alloy powder and using laser powder bed fusion technology to prepare key components is an important idea to reduce engine weight and improve engine service efficiency.However,in the current reports on laser powder bed fusion TiC/Inconel 718 composite,the mass fraction of nano-TiC particles added is mostly below 2%,and there is a lack of systematic and comprehensive research on the microstructure and properties of nickel-based composite with high TiC content.In addition,the microstructure evolution and precipitated phase behavior of the as-deposited samples after heat treatment still need to be further studied.Based on this,in this study,TiC/Inconel 718 nickel-based composite with nano-TiC mass fraction of 1.5%and 3%were added as the research object.The laser powder bed fusion experiment was carried out,and the deposited samples were heat treated to study the microstructure evolution and strengthening mechanism.The process-microstructure-mechanical properties relationship of TiC/Inconel 718 composite was established,and the contribution of different strengthening mechanisms to the yield strength of Inconel 718 alloy was clarified.It provides theoretical support for microstructure control and performance improvement of Inconel 718 alloy added with nano-TiC by laser powder bed fusion.The main conclusions of this study are as follows:(1)In the as-deposited TiC/Inconel 718 composite,the grains are mainly epitaxially grown columnar crystals,and the TiC partic les are uniformly and dispersedly distributed in the Inconel 718 matrix.TiC particles refine the microstructure of TiC/Inconel 718 composite,and the average grain size decreases from 9.56 μm to 8.43 μm.With the increase of TiC content,the difference of local microstructure in TiC/Inconel 718 composite molten pool is further reduced.The increase of the curvature radius of the fusion line of TiC/Inconel 718 composite further induces the epitaxial growth of dendrites,so that the maximum texture strength increases from 4.27 to 12.76.(2)Compared with as-deposited Inconel 718 alloy,the strength of the asdeposited TiC/Inconel 718 composite is significantly improved.Among them,the asdeposited 1.5 wt.%TiC/Inconel 718 com posite has the most obvious improvem ent effect,and the tensile strength and yield strength are increased by 121.7 MPa and 116.7 MPa,respectively.This is related to the nano-TiC particles hindering dislocation movement and bearing part of the load.During the deformation process,the pits caused by the debonding of TiC particles become the crack source and the channel of crack propagation,which reduces the elongation of the composite.(3)After heat treatment,MC phase is precipitated at the grain boundary of Inconel 718 alloy,while MC/M23C6 ph ase is precipitated at the grain boundary of TiC/Inconel 718 composite,and the number of MC/M23C6 precipitates increases with the increase of TiC content The heat-treated Inconel 718 alloy is completely recrystallized,and the grain structure is mainly composed of equiaxed grains,while the grain structure of the heattreated TiC/Inconel 718 composite is still columnar grains.(4)The mechanical properties of TiC/Inconel 718 composites after heat treatment are significantly improved due to the synergistic strengthening of TiC particles,γ" phase and γ’ phase.Compared with the heat-treated Inconel 718 alloy,the mechanical properties of the heat-treated l.5 wt.%TiC/Inconel 718 composite are improved most obviously at room temperature,and the yield strength and tensile strength are increased by 120.2 MPa and 83.5 MPa,respectively.The mechanical properties of the heat-treated 3 wt.%TiC/Inconel 718 composite improved most obviously at high temperature,and the yield strength and tensile strength are increased by 182.2 MPa and 162.3 MPa,respectively.However,the elongation of the two composites decreased to varying degrees.(5)During tensile test at room temperature,the fracture of MC/M23C6 phase at grain boundaries leads to crack initiation and propagation,which leads to the failure of heattreated TiC/Inconel 718 composite.In the high temperature tensile test,TiC/Inconel 718 composite are affected by the uneven grain size and the large area debonding of MC/M23C6 phase at the grain boundary,which makes TiC/Inconel 718 composite fail during high temperature tensile test.更多还原