K418高温合金叶轮脉冲激光再制造形状与性能控制

针对K418高温合金叶轮材料成本高、制造工艺复杂以及体积损伤频繁的实际,以该牌号体积损伤叶轮再制造为目标,设计了成分接近、工艺匹配的成形粉材,基于波形可调制 脉冲激光优化工艺,实现了形状和性能的再生。试验结果表明：叶片成形后表层及内部无裂纹,成形部位与基体为冶金结合,加工后尺寸精度在1mm以内,形变精度在0.03mm以内,成形层显微硬度为900~1400 HV0.1,超过基体20%。在高温动转平衡试验下,叶轮最大转数达13500 r/min,最大振幅0.4mm,无明显偏转及喘振现象,符合动平衡性能要求。     

激光熔覆Inconel718合金裂纹分析及裂纹控制研究

目的 针对K418合金表面激光熔覆裂纹萌生、元素偏析等难题,探究裂纹萌生与元素偏析之间的关系,利用后处理工艺进行裂纹的修复及偏析现象的控制。方法 在K418合金表面激光熔覆了Inconel718合金,以基体及熔覆材料的热物性参数和界面元素匹配性为出发点,对熔覆中裂纹的敏感性进行了分析。结果 合金元素的偏析造成了裂纹的萌生与扩展。基体热影响区裂纹的形成与热影响区内析出的块状碳氮化物有关,熔覆层裂纹与枝晶间析出的不规则链状Laves相有关。采用激光重熔工艺对熔覆层进行了后处理,试验结果表明,重熔后的组织致密,晶粒细小均匀,无裂纹及粘粉等明显缺陷。激光重熔减少了基体热影响区及熔覆层中因元素偏析产生的碳氮化物及Laves相的尺寸及数量,重熔后覆层的摩擦因数为0.55,比重熔前下降了49.5%,具有良好的减摩特性;磨损率为3.15×10-4 mm3/(N?mm),比重熔前下降了37.5%,耐磨性能得到提升。结论 激光重熔技术可以愈合K418激光熔覆Inconel718合金的裂纹,并显著降低涂层的元素偏析程度。     

K4104合金渗Al涂层抗高温氧化性能研究

采用料浆法在K4104合金表面进行热扩散渗铝,经1000℃×200h高温氧化性试验,用扫描电镜观察氧化后涂层的表面形貌。结果表明,渗Al涂层在氧化过程中已转变成连续致密的-αAl2O3氧化层和富铝的-βNiAl化合物层,使基体合金得到有效地保护,渗Al涂层具有良好的抗高温氧化性能。     

超细晶Inconel 718合金激光对接板的高温拉伸性能(英文)

为使Inconel 718合金的筒形多层夹芯结构顺利成形,研究该合金激光对接板的高温塑性。结果表明,拉伸方向对激光对接板的伸长率有很大影响。横向拉伸时,在温度为950°C和应变率为3.1×10-4s-1的条件下,最大伸长率为458.56%,此时m值为0.352,焊缝未变形。纵向拉伸时,在温度为965°C和应变速率为6.2×10-4s-1的条件下,最大延长率为178.96%,此时m值为0.261,焊缝随母材同时变形,焊缝的微观组织为树枝晶,晶间析出了Nb含量较高的Laves相。纵向拉伸时,由于动态再结晶的缘故,焊缝中出现了由树枝晶和等轴晶组成的混合组织。高温变形后,焊缝中的大量Laves相转化为δ相,但焊缝中仍有小部分残余的Laves相存在。多层夹芯筒结构成形的结果表明,激光对焊板的高温塑性能满足其筒形夹芯结构的要求。     

脉冲等离子增材再制造Inconel 718合金的组织演变

采用脉冲等离子工艺增材再制造了Inconel718镍基高温合金,并深入研究了再制造合金的组织形态及析出相分布规律,采用KGT模型对枝晶生长动力学进行定量计算。结果表明：沉积态合金组织以柱状枝晶为主,具有较强的外延生长特性,层与层之间有明显的界线。由于再制造过程中温度梯度和冷却速率的变化,自底部向顶部呈现胞状晶→柱状晶→粗大柱状枝晶→等轴晶的转变趋势,初生枝晶间距自底部向顶部分别为19.2、29.3和34.1 μm。大量不规则的Laves相分布在枝晶间,MC碳化物弥散分布于晶界。在中部及顶部,有（γ+Laves）共晶相生成。     

预制坡口角度对激光增材再制造IN718合金组织与性能的影响

目的研究在激光增材再制造IN718合金过程中,不同预制坡口角度对其组织与性能的影响。方法利用激光增材再制造技术对不同预制凹槽进行逐层叠加修复,采用光学显微镜观察显微组织,采用扫描电镜观察断口形貌,采用维氏硬度计对再制造试样进行硬度测量,采用残余应力测试仪测量再制造后基体表面的残余应力,采用万能拉伸试验机进行拉伸力学性能测试。结果当预制坡口角度大于130°时,能得到无组织缺陷、成形质量良好的增材再制造试样;当预制坡口角度小于110°时,修复界面会出现熔合不良现象,且修复区内部会出现裂纹。预制大的坡口角度进行激光增材再制造试验能获得组织更加细密、硬度分布更为均匀的再制造层,且大的坡口角度能有效降低再制造试样基体的残余应力。增大坡口角度有助于提高再制造试样的塑性,随着坡口角度的减小,再制造试样的力学性能变差。结论在进行激光增材再制造试验时,不宜预制过小的坡口角度,应根据损伤情况预制坡口角度较大的凹槽,有助于增加再制造成形件的组织均匀性,提高其力学性能。     

K418高温合金细晶叶片铸造工艺的研究

研究了Ｋ４１８高温合金细晶叶片铸造工艺。研究结果表明，在合适的型壳材料和合理的浇注系统条件下，当型壳温度控制在１０００℃，浇注时金属液过热温度控制在２８～３８℃，精炼温度不过高，则可获得健全的等轴细晶叶片。其晶粒度等级达到ＡＳＴＭ３０～６．０。     

高致密度激光选区熔化Inconel 718合金中的微小孔隙缺陷和拉伸性能

本文采用激光选区熔化技术制备了高致密度Inconel 718合金试样，研究了工艺参数（激光功率，扫描速度）对合金试样致密度的影响规律，分析了孔隙缺陷的形成原因，对比研究了微小孔隙缺陷存在条件下的拉伸性能变化，并比较了热处理对不同致密度合金力学性能影响。实验结果表明：工艺参数的改变决定了激光与粉末相互作用的模式，在较高激光功率、低扫描速度条件下发生了“匙孔”模式，气孔较多，致密度降低；当功率减小或者扫描速度增大会由“匙孔”模式向“热传导”模式转变，气孔较少，致密度会升高；但是当激光功率过小或者扫描速度过大时产生未熔合孔隙缺陷，使得材料的致密度出现大幅度减小的现象。拉伸测试结果表明，激光选区熔化成形Inconel 718合金的强度并不会随着致密度的增大呈严格单调增大的变化趋势，微小孔隙缺陷的形貌、数量和尺寸也会对拉伸性能产生影响。SIDA热处理可以大幅提高激光选区熔化成形Inconel 718合金的显微硬度及抗拉强度，但塑性呈显著降低。     

热处理对激光选区熔化制备Inconel 718合金组织和拉伸性能的影响

采用激光选区熔化工艺(SLM)制备了Inconel 718合金,并对合金分别进行了1050 ℃×1 h固溶和1050 ℃×1 h固溶+720 ℃×8 h+620 ℃×8 h双级时效热处理。结合微观组织、拉伸性能和断裂特征分析,研究了热处理工艺对SLM制备的Inconel 718合金组织和力学性能的影响。结果表明:固溶处理后合金内Laves相溶解,位错密度显著降低,材料的强塑性匹配较打印态得到良好的改善。经过时效热处理后,γ′和γ″强化相析出使合金强度大幅度提高的同时,保留了一定的塑性。     

Inconel 718合金激光处理的研究

采用Nd：YAG固体激光器在连续激光能量输入方式下对Inconel 718镍基超耐热合金进行表面激光处理，研究了激光处理工艺参数对该合金的微观组织、表面残余应力状态及疲劳性能的影响。结果表明：合金经激光处理后，原基体内弥散分布的γ″强化相及晶间片状δ相会溶解于基体γ相内，使得合金表面硬度下降，下降幅度约为50％；经低角度XRD检测，x、y方向表面残余应力均为拉应力；经激光处理的带缺口试样疲劳强度低于母材。     

油气工程用Inconel 718合金激光焊接头的氢脆行为

采用激光焊接工艺,对油气工程用4 mm厚经1030 ℃×2 h固溶+780 ℃×8 h时效和1030 ℃×2 h固溶+780 ℃×16 h时效两种热处理后的Inconel 718合金进行激光焊接,结合微观组织分析、拉伸性能分析和断口形貌分析,对合金母材及激光焊接头在原位充氢条件下的氢脆行为进行了研究。结果表明:长时间时效导致δ相大量析出,使合金母材的氢脆敏感性指数从正常时效态的0.27提高到过时效态的0.48。激光焊接头整体的氢脆敏感性没有受焊前热处理的影响,分别为0.39和0.38;由于焊缝内Laves相的析出,导致激光焊接头的氢脆敏感性高于正常时效态的母材。     

Microstructural characterization of Inconel 718 alloy after pulsed laser surface treatment at different powers

An annealed Inconel 718 alloy was surface-treated by pulsed laser at three different powers (100, 50 and 25 W). Microstructural changes induced by the laser treatments were characterized by use of electron backscatter diffraction and electron channeling contrast imaging techniques. Results show that both annealing twins and strengthening precipitates profusely existing in the as-received specimen are dissolved at elevated temperatures during the laser irradiation. Meanwhile, in the melting zone (MZ), densities of low angle boundaries (LABs) are greatly increased with a large number of Laves phases preferentially distributed along such LABs. For different specimens, widths and depths of their MZs are found to be gradually reduced with decreasing the laser powers. Orientation analyses reveal that the columnar grains in the MZ of the 100 W specimen could inherit orientations existing in the matrix while lower laser powers promote the formation of more nuclei with scattered orientations to grow to be granular grains in the MZ. Hardness tests reveal that the MZs of all laser-treated specimens are softer than the matrix probably due to both precipitate dissolution and grain coarsening.     

热处理对激光选区熔化成形Inconel 718合金显微组织结构和力学性能的影响

主要研究了激光选区熔化(selective laser melting,SLM)成形Inconel 718合金经固溶时效(SA)、均匀化+固溶时效(H+SA)、热等静压+固溶时效(HIP+SA)3种热处理后显微组织结构的转变与力学性能之间的关系.结果表明,沉积态试样的晶粒内部存在大量树枝晶结构,枝晶间析出了大量硬脆La...     

Study on wear mechanisms in drilling of Inconel 718 superalloy

The wear mechanisms and the approach to prolong the service life of the TiAlN coated carbide tool in drilling Inconel 718 superalloy are presented. It is found that the coated layer on the cutting edge is gradually abraded-off at the first stage of drill wear due to an excessive friction force on the tool–work interface. This in turns intensifies the friction force and leads to an increase of drilling force. Built-up edge (BUE) is then formed, and chipping starting from the relatively weaker cutting edge takes place subsequently. As a result, many micro-cracks are observed to distribute over the worn area. The subsurface fatigue cracks grow as the drilling process is proceeding. Together with the abrasion of hard carbide particles of the work material, the cutting edges break eventually parallel to the direction of fatigue cracks. At this moment, longer chip forms and cutting process is disturbed to an extent that the process can no longer be effectively continued. Failure of the drill is noted in a very short period of time once the long chips are observed. Finally, drilling experiments with the use of the cutting fluid containing the nano-particle low friction surface modifier are conducted. It is found that the service life of the drill is lengthened significantly and hence the machining cost can be greatly reduced.     

热处理对Inconel718合金组织及力学性能的影响

针对Inconel 718合金的不同用途,分析研究了4种常用热处理工艺对Inconel 718合金组织和力学性能的影响。结果表明:固溶温度超过1020℃时,奥氏体晶粒显著长大。合金中主要析出相有MC、δ、γ’和γ″相。δ相沿晶界分布,1025℃固溶时呈颗粒状少量析出;950℃固溶时呈块状大量析出;直接时效时呈网状不连续分布。同时,δ相对合金的晶粒度影响较大,且其析出数量和形态决定了合金的韧塑性,γ″、γ’相的析出量和尺寸与晶粒尺寸决定了合金的强度变化。     

Processing map for hot working of Inconel 718 alloy

Cylindrical specimens of Inconel 718 alloy with grain size of 90 μm were used in the compression tests and processing maps at the strains of 0.1, 0.3, 0.5 and 0.7 were developed at 950-1150 °C in the strain rate range 0.001-100 s⁻¹. Only one unstable region for adiabatic shear bands and one small dynamic recrystallization zone in the stable region are exhibited in the processing map at 0.1 strain. As the strain is beyond 0.3, there exist three unstable regions in the processing maps where one is for adiabatic shear bands and the other two are for intergranular cracking. At the same time, the zone of dynamic recrystallization with a peak efficiency of 0.39 at about 950 °C and 0.001 s⁻¹ in the stable region is enlarged and the distribution of which is from lower temperature and lower strain rate to higher ones. Optical micrographs of the specimens compressed to 0.7 strain show good agreement with the processing maps and main hot working schedules have been designed. Influence of initial grain size from 10 μm to 90 μm on the occurrence temperature of adiabatic shear bands and intergranular cracking has been analyzed at a strain rate of 100 s⁻¹ and in the temperature range 900-1200 °C.     

Evaluation of the mechanical properties of Inconel 718 components built by laser cladding

Laser-cladding process is one of the most relevant new processes in the industry due to the particular properties of the processed parts. The main users of this process are aeronautical turbine parts manufacturers and engineering maintenance services. The main advantage of laser-cladding process is the possibility of obtaining high quality material deposition on complex parts. Thus, laser cladding can be applied in the repair of high added-value and safety critical parts. This ability is especially useful for high-cost parts that present wears or local damage due to operating conditions. Different types of parts can be processed, such as housings, blades or even complete turbine rotors. Once the parts are repaired by laser cladding, they can be reassembled on the engine, reducing lead times. Laser-cladding process can permit buildup of complex geometries on previously forged or machined parts, such as stubs or flanges.However, one of the main drawbacks of the laser-cladding process currently is lack of knowledge on the properties of the deposited material. Most of the available data relate to the microstructure and the final hardness values. Nevertheless, there are few data of the mechanical properties of the parts. Moreover, it is difficult to gather data related to the influence of the laser-cladding parameters and strategies on the mechanical behaviour of a part.This paper presents the mechanical properties of a series of samples builtup by laser cladding. Two different types of specimens are tested: first, hybrid parts, in which laser cladding deposits materials built up layer-by-layer onto a substrate and the resulting part is a combination of deposited material and the substrate and second, complete rapid manufactured test samples. The results of tensile tests on various parts show that the laser-cladding strategy has a significant influence on their stress-strain curves. In addition, the laser-cladding process can result in a high directionality of their mechanical properties. The direction depends on the particular strategy in use. The study demonstrates that these properties present high anisotropy, a factor that should be carefully considered when selecting the most appropriate laser-cladding strategy.