Inconel 718合金螺栓滚压螺纹流线的检测方法

Inconel 718合金螺栓为航空发动机中常用的高强度螺栓,通常采用滚压螺纹成型工艺。螺栓及螺纹的流线直接影响螺栓的质量和服役寿命,所以流线检测尤为重要。通过试验,发现将Inconel 718合金螺栓进行二次固溶+时效处理可使其晶粒长大和析出δ相(Ni3Nb),然后在HNO3+HF的溶液中浸蚀1h,可以清晰显示出Inconel 718合金螺栓和螺纹的流线。     

高温保持对Inconel 718合金缺口敏感性的影响

研究了Inconel 718合金经980℃、1000℃及1020℃不同时间保温处理后,其缺口敏感性的变化规律,并采用扫描电镜(SEM)对拉伸断口及显微组织进行了分析.结果发现,经固溶、δ相时效、高温保持及双时效处理的Inconel718合金,980℃保温1h、6h时合金无缺口敏感性,但持久寿命较低;1000℃保温1h、3h、6h时,合金具有较好的高温持久性能;1020℃保温1h时则表现出了严重的缺口敏感性.Inconel 718合金经长时间高温保持处理后,基体中的δ相部分发生回溶,δ相含量太低是造成其缺口敏感的主要原因.     

Si3N4陶瓷/Nb/Cu/Ni/Inconel 600界面反应层形成机制研究

观察分析了Si3N4陶瓷/Nb/Cu/Ni/Inconel600界面处反应层的形貌、元素分布、反应层中的相结构、界面反应以及反应层的生长规律,研究了Si3N4陶瓷/Nb/Cu/Ni/Inconel600界面处反应层的形成机制.研究结果表明:在连接过程中,Cu层首先熔化,Nb、Ni向液态Cu中扩散溶解形成Cu-Nb-Ni合金,液态合金中的Nb和Ni向Si3N4表面扩散聚集并与Si3N4反应形成反应层;Si3N4侧的反应层主要物相是NbN和Nb、Ni的硅化物,Ni基合金侧反应相主要是NbNi3和Cu-Ni合金;在连接温度为1403 K的条件下,随着连接时间的增加,界面反应层厚度先快速增加,再缓慢增加.     

Inconel 718 激光焊接接头组织与热影响区裂纹研究

采用CO2激光器对板厚为11mm的Inconel 718合金进行激光焊接,并利用金相分析和扫描电镜对Inconel 718激光焊接接头各区域组织以及热影响区显微裂纹产生的原因进行了分析。研究发现:利用激光对Inconel718进行焊接,可以获得成形良好的焊接接头;焊缝区域组织为铸造组织,从熔合线到焊缝中心由较长的树枝晶逐步变为等轴晶;热影响区因受循环热输入的影响,晶界较母材出现粗化现象,且在钉头缩颈处出现沿粗化的晶界扩展的液化裂纹,裂纹两侧存在低熔点共晶体,主要富集Nb及Mo元素,低熔点共晶体在热输入影响下发生液化是裂纹产生的主要原因。     

Al、Ti含量对Inconel 718合金铸造组织和凝固行为的影响

采用差热分析(DSC)、光学显微镜、扫描电镜(SEM)、电子能谱(EDS)和X射线衍射分析(XRD)测试手段,结合JMatPro模拟计算分析研究了Al、Ti含量对Inconel 718铸锭组织和凝固行为的影响。结果表明,不同Al、Ti含量Inconel 718合金的铸态组织均呈典型树枝状结构,枝晶间析出相主要由(γ+Laves)共晶相和少量M(C,N)构成。随着Al/Ti原子比的升高,铸态组织中黑色枝晶间区域数量明显增加,Laves相形态由块状向共晶筛网状转变,同时Laves相周围析出的针状一次δ相和枝晶间γ″相数量减少;Inconel 718合金的凝固次序没有改变,合金的液相线由1363.5℃(合金Ⅰ)降低至1358.7℃(合金Ⅲ),而Laves相初熔温度和MC相固溶温度变化不大(不超过1.4℃);Nb,Mo,Ti元素在枝晶间的偏析程度随着Al/Ti原子比的升高而减轻。热力学计算结果显示,增加Al/Ti原子比可以提高γ′相数量,降低γ″相的数量。改型合金的硬度值随着Al/Ti原子比的提高而增加,当Al/Ti=4.32且(Al+Ti)=3.1at.%时,硬度值达到了345HV,比Inconel 718母合金硬度提高了23.7%。     

GH169合金中的γ''''、γ"及δ相

一、前言 GH169合金(Inconel 718)是一种时效硬化Ni-Cr-Fe基变形高温合金,在650℃下该合金具有很高的强度、韧性、疲劳性能及良好的综合性能。合金中主要有γ’、γ”、δ相以及各种夹杂相。 γ”相为亚稳相,是GH169合金的主要强化相;γ’相也是亚稳相,强化效果次于γ”相;δ相的组成虽与γ”相相同,但无明显的强化作用。γ’和γ”相的稳定性直接影响到合金的热稳定性。Wachtel和Rack总结有关Inconel718合金的研究,认为该合金中存在如下相反应: γ相→γ’相→γ”相→δ相 为提高合金的热稳定性,Pineau采用调整强化元素Nb、Ti、Al的比例和增加Mo元素来得到盘片状γ”相包覆立方形六面体γ’相的γ’相+γ”相包覆组织,但由于强化元素Nb含量的减少而导致合金强度下降。本文对不改变成分的GH169合金中γ’相和γ”相共格生长复合组织及δ相的一般特征进行研究。     

δ相对Inconel 718合金组织与疲劳性能影响的研究进展

Inconel 718合金中δ相数量与形貌的控制是保证产品性能的关键因素。介绍了近年来Inconel 718合金中δ相对其组织与疲劳性能影响的研究进展。综述了合金中δ相的形成与析出、溶解规律,δ相与热变形参数间的对应关系及δ相对疲劳性能的影响。     

O相合金Ti_2AlNb的研究进展

具有O相结构的Ti_2Al Nb合金是在Ti3Al系合金基础上拓展出来的新型金属间化合物材料,兼具了高的高温强度和相对较低的密度的特点,有望替代现有的Inconel 718镍基高温合金,用于制造高推重比航空发动机中的非转动部件甚至转动部件。概述了Ti_2Al Nb合金的特点和近年来我国在Ti_2Al Nb合金工程化研究方面取得的主要进展,对Ti_2Al Nb合金存在的不足以及当前研制过程中存在的主要问题进行了阐述,指出应立足于现有的钛合金冶炼和加工装备,并结合Ti_2Al Nb合金自身的特点,开发出成本更低、生产效率更高的工业化生产工艺技术。     

Inconel 600及Inconel 718合金晶界偏聚研究进展

高温合金中的溶质晶界偏聚是影响合金多方面性能的重要因素.以高温合金Inconel 600和Inconel718为研究对象,总结了合金中溶质晶界偏聚的研究现状,并对已有的研究成果进行了深入分析,结果发现:溶质在Inconel 600合金中的偏聚规律对舍金性能的影响还需要进一步研究晶界偏聚特性、基本物理参量以及晶间腐蚀抗力的作用;溶质在Inconel 718合金中的晶界偏聚对合金性能的影响依然有待于进一步研究其作用机理、偏聚动力学和共偏聚特性.同时,指出今后高温合金中溶质晶界偏聚的研究方向为溶质晶界偏聚动力学以及溶质问晶界共偏聚行为.     

Nb含量对发动机用激光增材成形Inconel925镍基高温合金组织和硬度的影响

为拓展激光增材工艺(LAM)在Inconel925镍基高温合金加工与修复方面的应用,采用球磨合金化方法制备了Inconel925合金粉末,以LAM工艺加工不同Nb含量的Inconel925试样,分析了Nb含量对发动机用LAM成形Inconel925镍基高温合金组织和硬度的影响。研究结果表明:当Nb含量上升后,形成了更加明显的二次枝晶臂,随着Nb含量增大,开始形成清晰的二次枝晶臂;当Nb加入量提高后,沉积态试样中枝晶干γ相含有的Nb比例升高。经过固溶处理试样在显微组织方面存在显著差异性。当固溶温度上升后,在基体内溶入了更多的枝晶间Laves相,得到了更加均匀的组织。固溶态试样在显微硬度方面都表现为随Nb含量的升高而增大,在Nb含量11%时沉积态试样达到最高显微硬度。当固溶温度上升后,试样硬度降低趋势也变得更加平缓。     

Multisheet structure of Inconel 718 superalloy processed by LBW/SPF technology and its microstructure

Abstract

Multisheet structure of Inconel 718 superalloy will be widely used in vehicles as heat resisting and heat shielding structure due to its lightweight, high strength and stiffness. Multisheet structure of Inconel 718 superalloy was processed by laser beam welding and superplastic forming (LBW/SPF) technology in the present paper. Multisheet structure of Inconel718 superalloy processed by LBW/SPF technology exhibits good configuration and uniform thickness distribution. Laser beam welding parameters for multisheet structure were as follows: pulse frequency was 32 Hz; pulse duration 3 ms; peak power per pulse 4500 W; welding speed 180 mm min^–1; SPF parameters were as follows: temperature T_f=965°C; forming pressure P _f=4·2 MPa; forming time t _f=130 min. Microstructure of multisheet structure was studied carefully. Microstructure in weld fusion zone was constituted of austenite dendritics and Laves phase precipitated in interdendritics. After SPF process, austenite dendritics in the weld fusion became coarser and most of Laves phases were dissolved and turned into δ precipitated phase but a few of Laves phases were still reserved. And Nb concentration in dendritics increased to 5·42% compared to 2·82% under as welded condition. Weld metal hardness increased from 331·63 under as welded condition to 391·74 under post-SPF condition which was closed to the base material hardness of post-SPF. Grain size of base material grew slightly and an amount of precipitated phase appeared in the base material undergoing SPF process. The tensile test results of base material show that tensile strength increased obviously and the ductility decreased slightly after SPF process. Therefore, LBW/SPF technology is an appropriate forming technique for multisheet structure of Inconel 718 superalloy.     

热输入对脉冲等离子弧增材制造Inconel 718合金组织与性能的影响

采用基于脉冲等离子弧的增材制造技术在Q235基板上加工了Inconel 718合金试样,通过改变功率和焊接速度研究了不同热输入对试样组织与性能演变规律的影响。借助光学显微镜、扫描电镜、能谱分析、维氏硬度仪等手段对试样晶粒形态、枝晶间距、元素偏析、析出相成分及分布、显微硬度等进行表征,结果表明随着热输入从1.08×106 J/m增大至1.76×106 J/m,晶粒形态从细长的柱状枝晶逐渐转变为粗大的胞状枝晶,枝晶间距从6.34μm增大至9.09μm,Nb、Mo等元素在枝晶间偏析加剧,Laves相由颗粒状、块状逐渐变为长链状,显微硬度不断下降。     

原位观察不同冷却速率下GH3625合金的凝固过程

利用带有红外加热炉的共聚焦激光扫描显微镜(CLSM)对GH3625高温合金在不同冷却速率(30℃/min、100℃/min和200℃/min)下的凝固过程进行了动态原位观察,通过差示扫描量热分析仪(DSC)、扫描电镜(SEM)和能谱仪(EDS)研究了凝固后的组织形态及相的析出规律。结果表明,GH3625合金的液相线温度在1 356.5℃,在凝固过程中自由表面液相分数随温度和时间的变化关系满足Avrami方程;凝固过程中主要相的析出顺序依次为γ基体相、碳化物和Laves相;在GH3625合金凝固过程中,随着冷却速率的增大,枝晶细化,枝晶间距减小,成分偏析减轻,Laves相分布更加弥散,且以析出共晶Laves相为主;凝固末期大量的Nb元素富集在枝晶间和晶界,这是形成Laves相的主要原因。     

Microstructure and mechanical properties of Inconel 718 electron beam welds

Abstract

Bead on plate, full penetration electron beam welds were produced in 2 mm thickness sheets of Inconel 718 in the solution treated condition. Welds were subjected to an aging treatment with and without post-weld solution treatment. Weld microstructures, high temperature tensile properties and stress rupture properties were evaluated. The as welded fusion zone showed a considerable amount of interdendritic niobium segregation and brittle intermetallic Laves phase. The tensile and stress rupture properties of the welds after post-weld aging treatment were found to be inferior in relation to the base metal. Post-weld solution treatment at 980°C was found to result in partial dissolution of Laves phase, some reduction in niobium segregation and the formation of δ phase needles around the Laves particles. The use of 980°C solution treatment was found to improve the weld properties to some extent, although not to the level of the base metal. The reasons for this behaviour are discussed, correlating microstructures, fracture features and mechanical properties.     

The formation and control of Laves phase in superalloy 718 welds

Weld heat input/cooling rate (affected by welding process, parameters, technique, tooling, etc.) was found to influence the microstructural characteristics and segregational features in alloy 718 welds, with low heat inputs proving beneficial. Laves phase formed in the interdendritic regions of the weld metals as a result of segregation. The morphology and composition of Laves phase depended strongly on heat input/cooling rate and influenced its response to subsequent homogenization post-weld heat treatment. The various factors affecting the formation and control of Laves phase in alloy 718 welds are highlighted. This revised version was published online in November 2006 with corrections to the Cover Date.     

Effect of flux addition on the microstructure and tensile strength of dissimilar weldments involving Inconel 718 and AISI 416

This research work articulates the microstructural features of the dissimilar weldments involving Ni based superalloy Inconel 718 and martensitic stainless steel, AISI 416 that is difficult to weld. Autogenous tungsten inert gas (TIG) welding was carried out with and without using flux to fabricate these bimetallic combinations. Microstructure at the fusion zones and the interfaces were characterized using optical and scanning electron microscopy. The results depicted the presence of fine martensite at the heat affected zone (HAZ) of AISI 416 and the formation of unmixed zone containing secondary phases at the HAZ of Inconel 718. Similarly, the formation of Nb rich eutectics along with sulfides was witnessed at the fusion zone of both the weldments. Owing to the low heat input witnessed during the flux assisted TIG welding, the Nb segregation was found to be minimal. Tensile studies reported that the fracture occurred at the fusion zone in both the cases. It was inferred from the tensile studies that the joint strength of the weldments with flux addition was greater than the ones without flux. This study demonstrated that dissimilar joints with complete penetration could be achieved in single pass using the TIG welding process with the aid of flux.     

Heat affected zone cracking in cast inconel 718

Electron beam welding parameters have been shown to influence heat-affected zone (HAZ) microfissuring behavior in cast Inconel 718 (Inconel is a trademark of INCO Alloys). Travel speed was shown to be the most significant factor in influencing HAZ cracking behavior by modifying the thermal gradient(s) and subsequently the stress state in the HAZ. This has been shown previously to be related to a change in weld pool geometry and to the effect of speed on heat flow in the weld zone.

Microfissuring in the HAZ was observed to occur intergranularly in areas containing Laves phase. Liquation of the Laves phase and subsequent wetting of the grain boundary is believed to be but one element of the complex interactions occuring in the HAZ during the weld thermal cycle.     

热处理工艺对Inconel718合金组织、力学性能及耐蚀性能的影响

对高含H2S/CO2酸性油气田封隔器材料-Inconel718镍基合金进行固溶处理和时效处理,研究不同热处理工艺条件下合金的组织、力学性能、耐蚀性能之间的关系。结果表明:随着固溶温度的升高,δ相不断溶入基体。材料经时效处理后析出第二相γ″相,硬度和强度明显高于固溶处理的样品,1000℃固溶+720℃×8h→50℃/h620℃×8h时效处理的样品硬度和强度达到最大值。高温高压H2S/CO2介质中挂片实验的结果表明,不同热处理的Inconel718合金均具有良好的耐腐蚀性能,经固溶处理的材料耐腐蚀性略优于经固溶+时效处理的材料。高温高压H2S/CO2应力腐蚀实验的结果表明,Inconel718没有发生应力腐蚀开裂迹象。综合考虑耐蚀性能和力学性能,确定Inconel718合金的最佳热处理工艺为:1000℃固溶1h+720℃×8h→50℃/h620℃×8h时效。     

The simultaneous improvements of strength and ductility in additive manufactured Ni-based superalloy via controlling cellular subgrain microstructure

Fine cellular subgrain structure was formed in the Selective Laser Melting(SLM) manu factured IN718 alloy via optimizing the processing parameters.During the subsequent homogenization heat treatment process,the Laves phase dispersed at the subgrain boundaries can be eliminated while the cellular subgrain structure is reserved in the printed samples after holding at 1080℃ for 50 min.With the prolongation of the holding time,the subgrain boundaries undergo low angle rotation via the motion ofdislocation,which leads to the annihilation of the cellular subgrain structure.Moreover,during the subsequent double aging heat treatment process,the reserved cellular subgrain structure in the homogenized samples promotes the precipitation of γ" second phase nanoparticles,and these precipitated γ" phase nanoparticles prefer to distribute at subgrain boundaries.It was found that these unique subgrain boundaries with γ" phase precipitates can hinder but not fully terminate the motion of dislocation during the plastic deformation process,which contributes to increasing the strength as well as holding the stable plastic flow.Hence,the strength and ductility of final prepared IN718 alloy with cellular subgrain microstructure were improved simultaneously compared to the prepared alloy without cellular subgrain structure,which even exceed the mechanical properties standards(AMS 5662) of wrought IN718 alloy.These results in our work suggest that controlling the subgrain structure is a promising effective strategy to improve the mechanical properties of SLM manu factured nickel-based superalloy.     

Microstructure and mechanical properties of nickel based superalloy IN718 produced by rapid prototyping with electron beam melting (EBM)

Abstract

A nickel alloy of a composition similar to that of the nickel based superalloy Inconel alloy 718 (IN718) was produced with the electron beam melting (EBM) process developed by Arcam AB. The microstructures of the as processed and heat treated material are similar to that of conventionally produced IN718, except that the EBM material showed some porosity and the δ phase did not dissolve during the solution heat treatment because the temperature of 1000°C apparently was too low. Mechanical testing of the layer structured material, parallel and perpendicular to the built layers, revealed sufficient strength in both directions. However, it showed only limited elongation when tested perpendicular to the built layers due to local agglomerations of pores. Otherwise, data for the hardness, Young’s modulus, 0·2% yield tensile strength and ultimate tensile strength match those recommended for IN718.