Cracking on a nickel-based superalloy fabricated by direct energy deposition

Cracks have consistently been a significant challenge limiting the development of additive manufactured nickel-based superalloys.It is essential to investigate the location of cracks and their forming mechanism.This study extensively examines the impact of solidification process,microstructural evolution,and stress concentration on crack initiation during direct energy deposition(DED).The results emphasize that the crack formation is significantly related to large-angle grain boundaries,rapid cooling rates.Cracks caused by large-angle grain boundaries and a fast-cooling rate predominantly appear near the edge of the deposited samples.Liquation cracks are more likely to form near the top of the deposited sample,due to the presence ofγ/γ'eutectics.The secondary dendritic arm and the carbides in the interdendritic regions can obstruct liquid flow during the final stage of solidification,which results in the formation of solidification cracks and voids.This work paves the way to avoid cracks in nickel-based superalloys fabricated by DED,thereby enhancing the performance of superalloys.

Recent advances in nickel-based catalysts in eCO_(2)RR for carbon neutrality

The excessive use of nonrenewable energy has brought about serious greenhouse effect.Converting CO_(2) into high-value-added chemicals is undoubtedly the best choice to solve energy problems.Due to the excellent cost-effectiveness and dramatic catalytic performance,nickel-based catalysts have been considered as the most promising candidates for the electrocatalytic CO_(2) reduction reaction(eCO_(2)RR).In this work,the electrocatalytic reduction mechanism of CO_(2) over Ni-based materials is reviewed.The strategies to improve the eCO_(2)RR performance are emphasized.Moreover,the research on Ni-based materials for syngas generation is briefly summarized.Finally,the prospects of nickel-based materials in the eCO_(2)RR are provided with the hope of improving transition-metal-based electrocatalysts for eCO_(2)RR in the future.

Effect of Interface Form on Creep Failure and Life of Dissimilar Metal Welds Involving Nickel-Based Weld Metal and Ferritic Base Metal

For dissimilar metal welds(DMWs)involving nickel-based weld metal(WM)and ferritic heat resistant steel base metal(BM)in power plants,there must be an interface between WM and BM,and this interface suffers mechanical and microstructure mismatches and is often the rupture location of premature failure.In this study,a new form of WM/BM interface form,namely double Y-type interface was designed for the DMWs.Creep behaviors and life of DMWs containing double Y-type interface and conventional I-type interface were compared by finite element analysis and creep tests,and creep failure mechanisms were investigated by stress-strain analysis and microstructure characterization.By applying double Y-type interface instead of conventional I-type interface,failure location of DMW could be shifted from the WM/ferritic heat-affected zone(HAZ)interface into the ferritic HAZ or even the ferritic BM,and the failure mode change improved the creep life of DMW.The interface premature failure of I-type interface DMW was related to the coupling effect of microstructure degradation,stress and strain concentrations,and oxide notch on the WM/HAZ interface.The creep failure of double Y-type interface DMW was the result of Type IV fracture due to the creep voids and micro-cracks on fine-grain boundaries in HAZ,which was a result of the matrix softening of HAZ and lack of precipitate pinning at fine-grain boundaries.The double Y-type interface form separated the stress and strain concentrations in DMW from the WM/HAZ interface,preventing the trigger effect of oxide notch on interface failure and inhibiting the interfacial microstructure cracking.It is a novel scheme to prolong creep life and enhance reliability of DMW,by means of optimizing the interface form,decoupling the damage factors from WM/HAZ interface,and then changing the failure mechanism and shifting the failure location.

血清可溶性CD276与晚期高级别浆液性卵巢癌预后及肿瘤免疫浸润相关性分析

目的探讨血清可溶性CD276(sCD276)与晚期高级别浆液性卵巢癌(HGSOC)预后及肿瘤免疫浸润的相关性。方法将2017年3月至2020年3月资阳市第一人民医院就诊的晚期HGSOC患者73例纳入A组,选取同期入院治疗的其他类型卵巢癌患者80例纳入B组,另选择80名健康人群作为健康人群组,检测三组血清sCD276表达水平。并依据血清sCD276表达水平中位数将A组分为高表达组(≥451.26 pg/ml)与低表达组(<451.26 pg/ml)。分析血清sCD276水平变化与晚期HGSOC患者不同临床特征的关系,并采用生存曲线和Cox比例风险回归分析血清sCD276与晚期HGSOC预后的相关性。结果A组和B组血清sCD276表达水平均高于健康人群组(P<0.05),且A组血清sCD276水平高于B组(P<0.05);卵巢癌患者sCD276低表达与高表达的无病生存率比较,差异无统计学意义(P>0.05);在A组中,低表达组的无病生存率及总生存率高于高表达组(P<0.05),无病生存时间≥12月组的血清sCD276表达水平低于无病生存时间<12月组(P<0.05);A组患者中sCD276高表达组与低表达组在有无淋巴结转移、术后残余病灶、CD3^(+)阳性、FoxP3^(+)阳性等方面比较有差异统计学意义(P<0.05);经多因素COX比例风险回归分析得出,有术后残余病灶、CD3^(+)阳性、FoxP3^(+)阳性、血清sCD276≥451.26 pg/ml均是晚期HGSOC患者预后的危险因素(P<0.05);经免疫组化法对肿瘤组织检测得出,A组中有59例患者膜CD276表达为阳性,14例患者膜CD276表达为阴性,膜CD276阳性组的血清sCD276表达及FoxP3^(+)阳性比例均明显高于膜CD276阴性组(P<0.05)。结论血清sCD276在晚期HGSOC呈高表达水平,其水平升高与TILs标志物FoxP3^(+)T细胞数量均是晚期HGSOC患者复发或死亡的危险因素,与患者预后关系密切,血清sCD276为晚期HGSOC新辅助化疗期间的免疫应答监测提供了可能性。

Effect of the capsule on deformation and densification behavior of nickel-based superalloy compact during hot isostatic pressing

The Shima yield criterion used in finite element analysis for nickel-based superalloy powder compact during hot isostatic pressing(HIP) was modified through uniaxial compression experiments. The influence of cylindrical capsule characteristics on FGH4096M superalloy powder compact deformation and densification behavior during HIP was investigated through simulations and experiments. Results revealed the simulation shrinkage prediction fitted well with the experimental shrinkage including a maximum shrinkage error of 1.5%. It was shown that the axial shrinkage was 1.7% higher than radial shrinkage for a cylindrical capsule with the size of ∮50 mm × 100 mm due to the force arm difference along the axial and radial direction of the capsule. The stress deviated from the isostatic state in the capsule led to the uneven shrinkage and non-uniform densification of the powder compact. The ratio of the maximum radial displacement to axial displacement increased from0.47 to 0.75 with the capsule thickness increasing from 2 to 4 mm. The pressure transmission is related to the capsule thickness, the capsule material performance, and physical parameters in the HIP process.

肌层浸润性膀胱癌中CD276的表达与临床病理特征和预后的相关性

目的CD276的异常表达已被证实与肿瘤的发生有关。但其在肌层浸润性膀胱癌(MIBC)中的作用知之甚少。方法从癌症基因组图谱数据库中下载MIBC患者的相关数据,通过研究CD276在膀胱正常组织和肿瘤组织中的表达差异,同时评估临床变量与CD276之间的相关性来预测CD276与MIBC的生存预后。采用Cox回归分析和人类蛋白质图谱证明CD276是MIBC的独立预测因子。最后使用基因集富集分析(GSEA)数据集进行分析。结果MIBC的肿瘤分级、分期、发病年龄和N分期与CD276的高表达有关。CD276高表达患者预后较CD276低表达者差。单因素和多因素回归分析显示,CD276是MIBC的独立危险因素。GSEA富集分析发现CD276主要富集于肿瘤相关通路、膀胱癌、细胞黏附分子、ECM受体相互作用、Wnt信号通路、趋化因子信号通路以及MAPK信号通路。结论CD276在MIBC中高表达,其可作为MIBC预后的潜在独立分子标志物。

烧结工艺对Hastelloy C-276多孔滤管性能的影响

文章中采用粉末冶金方法制备了Hastelloy C-276多孔滤管,研究了烧结工艺对滤管性能的影响。通过研究显示真空气氛烧结更适合于滤管的制备;真空气氛烧结的性能明显优于氢气气氛烧结;真空气氛下烧结后,滤管表面灰白洁净、光亮,烧结颈光滑,孔道圆润;随着烧结温度的升高,平均孔径由6.3μm降至4.5μm,透气度由65.1m^(3)/m^(2)·h·KPa降至53.2m^(3)/m^(2)·h·KPa;压溃强度由156MPa提高到254MPa,环拉强度由78MPa提高到127MPa。本次实验中最佳烧结工艺为:真空气氛烧结,1250~1300℃下保温2h。

哈氏合金C-276管束在PTA装置尾气中腐蚀的关键因素分析

某石化PTA装置尾气催化燃烧第一预热器哈氏合金C-276管束在运行13年后出现管束进口100~300 mm范围腐蚀问题,在更换同材质换热器管束后,仅运行三个半月又发生同样的腐蚀现象。针对上述问题,通过对比运行时间、操作条件、介质成分变化等因素,结合换热管腐蚀形貌、腐蚀产物能谱分析,以及换热管内流动进口区速度边界层分析结果,研究了C-276管束在进口端发生的高腐蚀速率行为,确定了腐蚀机理,得出尾气中水分的增加是导致腐蚀失效的关键因素的结论,同时,根据分析结果提出了相应的防护建议。

Research progress on selective laser melting processing for nickel-based superalloy

Selective laser melting(SLM),an additive manufacturing process mostly applied in the metal material field,can fabricate complex-shaped metal objects with high precision.Nickel-based superalloy exhibits excellent mechanical properties at elevated temperatures and plays an important role in the aviation industry.This paper emphasizes the research of SLM processed Inconel 718,Inconel 625,CM247LC,and Hastelloy X,which are typical alloys with different strengthening mechanisms and operating temperatures.The strengthening mechanism and phase change evolution of different nickel-based superalloys under laser irradiation are discussed.The influence of laser parameters and the heat-treatment process on mechanical properties of SLM nickel-based superalloys are systematically introduced.Moreover,the attractive in-dustrial applications of SLM nickel-based superalloy and printed components are presented.Finally,the prospects for nickel-based superalloy materials for SLM technology are presented.

Research on CMT welding of nickel-based alloy with stainless steel

Cold Metal Transfer （CMT） welding technique is a new welding technique introduced by Fronins company. CMT welding of nickel-based alloy with stainless steel was carried out using CuSi3 filler wire in this paper. Effects of welding parameters, including welding current, welding speed, etc, on weld surface appearance were tested. Microstructure and mechanical properties of CMT weld were studied. The results shaw that the thickness of interface reaction layer of the nickel- based alloy is 14. 3 μm, which is only 4. 33% of base material. The weld is made up of two phases, α-copper and iron-based solid solution. Rupture occurs initially at the welded seam near the edge of stainless steel in shear test. The maximum shear strength of the CuSi3 welded joint is 184. 9 MPa.

TEMPERATURE EFFECT ON LOW-CYCLE FATIGUE BEHAVIOR OF NICKEL-BASED SINGLE CRYSTALLINE SUPERALLOY

The low-cycle fatigue （LCF） behavior of a nickel-based single crystal superalloy with [001] orientation was studied at an intermediate temperature of T0℃ and a higher temperature of To ＋ 250℃ under a constant low strain rate of 10^-3 s^-1 in ambient atmosphere. The superalloy exhibited cyclic tension-compression asymmetry which is dependent on the temperature and applied strain amplitude. Analysis on the fracture surfaces showed that the surface and subsurface casting micropores were the major crack initiation sites. Interior Ta-rich carbides were frequently observed in all specimens. Two distinct types of fracture were suggested by fractogaphy. One type was characterized by Mode-I cracking with a microscopically rough surface at To ＋ 250℃. Whereas the other type at lower temperature T0℃ favored either one or several of the octahedral {111} planes, in contrast to the normal Mode-I growth mode typically observed at low loading frequencies （several Hz）. The failure mechanisms for two cracking modes are shearing of γ＇ precipitates together with the matrix at T0℃ and cracking confined in the matrix and the γ/γ＇interface at To - 250℃.

Effects of sol-gel method and lanthanum addition on catalytic performances of nickel-based catalysts for methane reforming with carbon dioxide

The nickel-based catalysts were prepared by the sol-gel method and used for the CH4 reforming with CO2. The effects of the sol-gel method on the specific surface area, catalytic activity, desorption, and reduction performances of catalysts were investigated with BET, TPR, and TPD. Compared with the catalyst prepared by the impregnation method, the results indicated that the catalysts prepared by the sol-gel method had larger specific surface area, showing higher catalytic activities and exhibiting perfect desorption and reduction performances. In addition, the modification effects of adding La were studied, and it was found that the 0.75NLBT catalyst constituted of 5wt.%Ni-0.75wt.%La was optimal.

Surface characteristics of rapidly solidified nickel-based superalloy pow-ders prepared by PREP

The surface microstructure and the surface segregation of FGH 95 nickel-basedsuperalloy powders prepared through plasma rotating electrode processing (PREP) have beeninvestigated by using SEM and AES. The results indicate that the surface microstructure of powderschanges from dendrite into cellular stricture as the particle size of powders decrease, and thepredominant precipitates solidified on the particle surfaces were identified as MC' type carbidesenriched with Nb and Ti. It was also indicated that along with the depth of particle surfaces, thesegregation layer of S, C and O elements are thick, and that of Ti, Cr elements are thin for largesire powders while they are in reverse for median size particles.

Creep feed grinding induced gradient microstructures in the superficial layer of turbine blade root of single crystal nickel-based superalloy

The service performance of the turbine blade root of an aero-engine depends on the microstructures in its superficial layer.This work investigated the surface deformation structures of turbine blade root of single crystal nickel-based superalloy produced under different creep feed grinding conditions.Gradient microstructures in the superficial layer were clarified and composed of a severely deformed layer(DFL)with nano-sized grains(48–67 nm)at the topmost surface,a DFL with submicron-sized grains(66–158 nm)and micron-sized laminated structures at the subsurface,and a dislocation accumulated layer extending to the bulk material.The formation of such gradient microstructures was found to be related to the graded variations in the plastic strain and strain rate induced in the creep feed grinding process,which were as high as 6.67 and 8.17×10^(7)s^(−1),respectively.In the current study,the evolution of surface gradient microstructures was essentially a transition process from a coarse single crystal to nano-sized grains and,simultaneously,from one orientation of a single crystal to random orientations of polycrystals,during which the dislocation slips dominated the creep feed grinding induced microstructure deformation of single crystal nickel-based superalloy.

Microstructure and mechanical properties of nickel-based superalloy fabricated by laser powder-bed fusion using recycled powders

Evaluating the recyclability of powders in additive manufacturing has been a long-term challenge.In this study,the microstructure and mechanical properties of a nickel-based superalloy fabricated by laser powder-bed fusion(LPBF)using recycled powders were investigated.Re-melted powder surfaces,satellite particles,and deformed powders were found in the recycled powders,combined with a high-oxygencontent surface layer.The increasing oxygen content led to the formation of high-density oxide inclusions;moreover,printing-induced cracks widely occurred and mainly formed along the grain boundaries in the as-built LPBF nickel-based superalloys fabricated using recycled powders.A little change in the Si or Mn content did not increase the hot cracking susceptibility(HCS)of the printed parts.The changing aspect ratio and the surface damage of the recycled powders might contribute to increasing the crack density.Moreover,the configuration of cracks in the as-built parts led to anisotropic mechanical properties,mainly resulting in extremely low ductility vertical to the building direction,and the cracks mainly propagated along the cellular boundary owing to the existence of a brittle precipitation phase.

Effect of TiC addition on the microstructure and wear resistance of induction brazed nickel-based coating in air

The nickel-based coating with different TiC addition was fabricated onto 45 steel substrate by using induction brazed technology in air.The effect of TiC addition on the microstructure and wear resistance of induction brazing coating was studied.The results show that the microstructure of brazing coating is strengthened and refined by adding TiC.With the increase of the amount of TiC added,the amount of TiC in the Ni-based matrix is increased,and the matrix structure is obviously refined.This is because the high melting point TiC particles can be used as heterogeneous nucleation cores,thus refining the Ni based matrix structure.Moreover,the wear resistance of brazing coating is improved due to the addition of TiC.

A critical review on nickel-based cathodes in rechargeable batteries

The 3d transition-metal nickel(Ni)-based cathodes have long been widely used in rechargeable batteries for over 100 years,from Ni-based alkaline rechargeable batteries,such as nickel-cadmium(Ni-Cd)and nickel-metal hydride(Ni-MH)batteries,to the Ni-rich cathode featured in lithium-ion batteries(LIBs).Ni-based alkaline batteries were first invented in the 1900s,and the well-developed Ni-MH batteries were used on a large scale in Toyota Prius vehicles in the mid-1990s.Around the same time,however,Sony Corporation commercialized the first LIBs in camcorders.After temporally fading as LiCoO_(2) dominated the cathode in LIBs,nickel oxide-based cathodes eventually found their way back to the mainstreaming battery industry.The uniqueness of Ni in batteries is that it helps to deliver high energy density and great storage capacity at a low cost.This review mainly provides a comprehensive overview of the key role of Ni-based cathodes in rechargeable batteries.After presenting the physical and chemical properties of the 3d transition-metal Ni,which make it an optimal cationic redox center in the cathode of batteries,we introduce the structure,reaction mechanism,and modification of nickel hydroxide electrode in Ni-Cd and Ni-MH rechargeable batteries.We then move on to the Ni-based layered oxide cathode in LIBs,with a focus on the structure,issues,and challenges of layered oxides,LiNiO_(2),and LiNi_(1−x−y)Co_(x)Mn_(y)O_(2).The role of Ni in the electrochemical performance and thermal stability of the Ni-rich cathode is highlighted.By bridging the“old”Ni-based batteries and the“modern”Ni-rich cathode in the LIBs,this review is committed to providing insights into the Ni-based electrochemistry and material design,which have been under research and development for over 100 years.This overview would shed new light on the development of advanced Ni-containing batteries with high energy density and long cycle life.

Microstructural evolution and castability prediction in newly designed modern third-generation nickel-based superalloys

The present research aims to establish a quantitative relation between microstructure and chemical composition （i.e., Ti, Al, and Nb） of newly designed nickel-based superalloys. This research attempts to identify an optimum microstructure at which the minimum quanti- fies of γ/γ＇ and γ/γ＂ compounds are achieved and the best castability is predicted. The results demonstrate that the highest quantity of inter- metallic eutectics （i.e., 41.5wt%） is formed at 9.8wt% （Ti ＋ A1）. A significant quantity of intermetallics formed in superalloy 1 （with a com- position of7 - 9.8wt% （Ti ＋ A1））, which can deteriorate its castability. The type and morphology of the eutectics changed and the amount considerably decreased with decreasing Ti ＋ A1 content in superalloy 2 （with a composition ofy - 7.6wt% （Ti ＋ A1）, 1.Swt% Nb）. Thus, it is predicted that the castability would improve for superalloy 2. The same trend was observed for superalloy 4 （with a composition of 7 - 3.7wt% （Ti ＋ A1）, 4.4wt% Nb）. This means that the amount of Laves increases with increasing Nb （to 4.4wt%） and decreasing Ti ＋ A1 （to 3.7wt%） in su- peralloy 4. The best castability was predicted for superalloy 3 （with a composition ofy - 5.7wt% （Ti ＋ A1）, 2.8wt% Nb）.

Isothermal oxidation behavior and mechanism of a nickel-based superalloy at 1000°C

The oxidation behavior of a nickel-based superalloy at 1000°C in air was investigated through X-ray diffraction, scanning electron microscopy, and energy-dispersive spectroscopy analysis. A series of oxides, including external oxide scales（Cr_2O_3,（TiO_2 ＋ Mn Cr_2O_4）） and internal oxides（Al_2O_3,Ti N）, were formed on the surface or sub-surface of the substrate at 1000°C in experimental still air. The oxidation resistance of the alloy was dependent on the stability of the surface oxide layer. The continuity and density of the protective Cr_2O_3 scale were affected by minor alloying elements such as Ti and Mn. The outermost oxide scale was composed of TiO_2 rutile and Mn Cr_2O_4 spinel, and the growth of TiO_2 particles was controlled by the outer diffusion of Ti ions through the pre-existing oxide layer. Severe internal oxidation occurred beneath the external oxide scale, consuming Al and Ti of the strength phase γ′（Ni_3（Al,Ti）） and thereby severely deteriorating the surface mechanical properties. The depth of the internal oxidation region was approximately 35 μm after exposure to experimental air at 1000°C for 80 h.