Inconel 740H合金750℃长期时效后的组织稳定性

对Inconel 740H合金管材在750℃进行500~3000h的无应力时效实验,采用热力学模拟,OM,FEG-SEM,显微硬度测定等方法研究了合金微观组织及显微硬度的变化趋势。结果表明:供货态(固溶处理)管材的合金成分及拉伸性能等均满足ASME要求,管材合格;长期时效后合金的主要析出相为γ′及M23C6,无η,σ等有害相析出。随着时效时间的延长,γ′粒子的粗化速率较快,其规律符合LSW熟化理论,M23C6相尺寸变化不明显;合金的显微硬度呈现先上升后下降的变化趋势,但整体波动较小。长期时效后合金组织及显微硬度的变化表明Inconel 740H在750℃/3000h条件下的组织稳定性较好,可用于进一步进行持久等长时力学性能的检验。     

热丝TIG堆焊Inconel 625层组织成形研究

采用热丝钨极惰性气体保护焊,用ENiCrMo-3型焊丝在Q235B钢管内表面进行堆焊试验。利用金相显微镜、扫描电镜、X射线衍射仪对堆焊层微观组织进行观察和元素成分分析,利用显微硬度计测定试样硬度分布。结果表明,堆焊层组织主要为γ-Ni单相奥氏体,在晶界处有碳化物析出;堆焊层组织自熔合线至顶部的基本形态依次为平面晶、胞晶、树枝晶、等轴晶及顶部横向柱状晶;熔合线附近有少量魏氏体组织形成;试样硬度自基材至堆焊层方向呈递增趋势;上层组织在晶界位置贫Cr较下层严重,从金相看其晶粒受到的侵蚀作用更明显。     

冷拉减面率对C形环用Inconel X-750丝材组织性能的影响

文章通过冷拉拔加工制备减面率为0%、30%、60%的Inconel X-750丝材,分别在650℃、730℃、810℃下时效处理16h,研究冷拉减面率对X-750合金组织性能的影响,特别是减面率对γ′相形状、分布、数量及尺寸的影响。经定量分析,增大冷拉减面率除了有细化晶粒的作用外,还能一定程度地增加γ′相析出的颗粒数量及体积分数,减小γ′相尺寸,进一步加强沉淀强化的作用。时效温度对X-750丝材的晶粒尺寸没有明显影响,对γ′相的数量、尺寸及形状影响较大。采用730℃时效处理16h的标准工艺制备的X-750丝材,经加工为弹簧后制造成金属C形密封环,其回弹量及泄漏率均满足要求,实验条件下密封性能良好。     

Experimental investigations into electric discharge grinding and ultrasonic vibration-assisted electric discharge grinding of Inconel 601

The paper presents experimental investigations into electric discharge grinding (EDG) and ultrasonic vibration-assisted electric discharge grinding (UVAEDG) of Inconel 601. The process parameters selected for both processes were duty cycle, discharge current, pulse on time, grinding wheel speed, work speed, and speed ratio to study their influence on responses like surface roughness (R_a) and material removal rate (MRR). It was found that duty cycle, wheel speed, work speed, discharge current, speed ratio, and pulse duration significantly influenced MRR and R_a. It was inferred that MRR increased with increase in duty cycle, wheel speed, current, work speed, and pulse duration in both EDG and UVAEDG processes. It was also inferred that R_a increased with rise in duty factor, pulse on time, and discharge current in EDG and UVAEDG processes.     

Welding current influences on Inconel 625/X65 cladding interface

The pulsed gas tungsten arc welding with hot wire was used to clad Inconel 625 on the surface of X65 steel. The influences of welding current in horizontal welding position on the dilution, in further the composition, microstructure, and property of the Inconel 625/X65 cladding interface were investigated. Experimental results show that with the increase in welding current, namely, in heat input and arc force, dilution rate increased; the composition transition region in the cladding layer close to the fusion line, controlled by the cladding temperature, would be widen; in further, the microstructure would be different due to the heat transfer and composition change; the precipitates were niobium-rich MC carbide with a low welding current, but tended to be the intermetallic compounds, Laves phase, with a high welding current; the highest and lowest hardness values appeared on the heat-affected zone and cladding layer next to the bonding interface, respectively.     

Functional encapsulation of laser melted Inconel 718 by Arc-PVD and HVOF for post compacting by hot isostatic pressing

In this study, the Selective Laser Melting (SLM) technology was used to manufacture flat specimens from Inconel 718 powder. The SLM process parameters have a major impact on the microstructure as well as on the mechanical properties of the fabricated specimens. Despite using optimized processing parameters, defects like pores cannot be completely avoided. These pores act as stress raisers and lead to premature crack initiation under cyclic loading, eventually reducing the fatigue strength of the material. Hot Isostatic Pressing (HIP) offers the possibility to eliminate the porosity and thus to increase the fatigue performance of the material. HIP combines high pressure and high temperature to produce materials with superior properties. Unfortunately, open porosity, i.e. open pores on the surface, can prevent full densification. In the present work, SLM flat specimens were encapsulated by means of Cathodic Arc Deposition (Arc-PVD) and High Velocity Oxygen Fuel Spraying (HVOF) to seal open pores. For this purpose, different encapsulation materials were investigated with a focus on materials offering additional functions such as an improved high temperature corrosion resistance or applicability as a bond coat for thermal barrier coatings.     

Study on ductility-dip cracking susceptibility in filler metal 52M during welding

Alloy 690 is a typical Ni-Cr-Fe alloy,which is widely used in nuclear power application.However,filler metal 52M (FM-52M) used in alloy 690 weldment is found to be susceptible to ductility-dip cracking...     

低C含Cu NV-F690特厚钢板的精细组织和强韧性

本文通过板坯连铸、钢板控轧控冷(TMCP)、固溶淬火回火(QT)工业生产流程,开发低C含Cu高强韧NV-F690特厚(厚度t为80 mm)船体和海洋平台用钢板.使用SEM,EBSD和TEM分别研究了淬火(Q)态和QT态钢板的精细组织,测试了距离钢板表面t/4处(高冷却速率)和芯部t/2处(低冷却速率)的室温硬度和拉伸性能,在-60和-80℃下进行了Charpy冲击(Charpy V notch,CVN)示波实验.结果表明,淬火速率较大有利于板条组织形成和提高大角度晶界比例,t/4处的组织为板条状贝氏体(LB),板条间存在细小片状马氏体/奥氏体(M/A)组元,晶粒间大角度晶界(>15°)体积分数为67.5%;t/2处的组织为粒状贝氏体(GB)+LB,大角度晶界体积分数为63.0%;Q态下的LB具有高位错密度,但晶粒内不存在Cu析出相.经过650℃回火150 min,钢板的强韧性匹配优良,低温下呈韧性断裂,大量含Cu弥散沉淀相在基体组织内析出.t/2处的M/A组元分解为Cr-Mo碳化物,贝氏体板条宽度为0.4μm,大角度晶界分数为62.5%;t/4处的LB板条回复,板条内存在与基体取向差较大的亚晶,大角度晶界分数提高到71.7%,板条平均宽度为0.2μm.在-80℃下,NV-F690钢板t/4处的韧性高于t/2处的韧性.随着纤维断裂位移的增大,韧窝断裂区比例和韧窝尺寸逐渐增大,NV-F690钢低温Charpy冲击能量逐渐提高.     

Design and statistical analysis of plasma coatings on superalloy for gas turbine applications

The Influence of plasma sprayed NiCr–Cr₂O₃ and Al₂O₃–40% TiO₂ (A40T) coatings on Inconel 617 are investigated at 900 and 1000 °C under mixed salt environment for gas turbine applications. The results revealed that the plasma coated alloy exhibits lower mass change than bare alloy in the Na₂SO₄ and NaCl salt mixture with and without V₂O₅. The response to the experimental analysis is statistically evaluated using 2³ factorial design. Further the exposed samples were analyzed by means of optical image, SEM, EDS and XRD results. The EDS and XRD analysis revealed that the oxides are rich in Ni and Mo on the surface of the samples. The coated samples exhibited better corrosion resistance in A40T when compared to NiCr–Cr₂O₃ coatings than bare alloy.     

A Comprehensive Comparison of the Analytical and Numerical Prediction of the Thermal History and Solidification Microstructure of Inconel 718 Products Made by Laser Powder-Bed Fusion

The finite-element (FE) model and the Rosenthal equation are used to study the thermal and microstructural phenomena in the laser powder-bed fusion of Inconel 718. A primary aim is to comprehend the advantages and disadvantages of the Rosenthal equation (which provides an analytical alternative to FE analysis), and to investigate the influence of underlying assumptions on estimated results. Various physical characteristics are compared among the FE model, Rosenthal equation, and experiments. The predicted melt pool shapes compared with reported experimental results from the literature show that both the FE model and the analytical (Rosenthal) equation provide a reasonably accurate estimation. At high heat input, under conditions leading to keyholing, the reported melt width is narrower than predicted by the analytical equation. Moreover, a sensitivity analysis based on choices of the absorptivity is performed, which shows that the Rosenthal approach is more sensitive to absorptivity, compared with the FE approach. The primary reason could be the effect of radiative and convective losses, which are assumed to be negligible in the Rosenthal equation. In addition, both methods predict a columnar solidification microstructure, which agrees well with experimental reports, and the primary dendrite arm spacing (PDAS) predicted with the two approaches is comparable with measurements.