Thermo-physical properties of Hastelloy X and Haynes 214 close to the melting range

ABSTRACT

The nickel-based superalloys Hastelloy X and Haynes 214 are widely used for honeycomb liners; however, thermo-physical properties at temperatures close to the melting range are poorly described in the literature. Based on the thermo-physical properties, endothermic effects between 550°C and 650°C have been observed that develop due to the formation of the short-range order in both alloys and in Haynes 214, in addition to the short-range order, an increase in the specific heat capacity due to the γ′-precipitation up to 950° was detected. At low and intermediate temperatures, the Hastelloy X is significantly better suited than the Haynes 214. At high temperatures the Haynes 214 is superior to the Hastelloy X due to the dissolution of the γ′-phase.     

哈氏合金X电子束表面处理微观组织研究

哈氏合金因其优良性能被广泛应用于航空工业,利用强流脉冲电子束(HCPEB)轰击哈氏合金X表面对其进行改性,并对其显微组织进行分析和讨论。利用扫描电子显微镜(SEM)观察腐蚀后试样,利用电子背散射衍射(EBSD)观察未腐蚀试样。结果表明：从扫描电镜照片可以看到,未轰击试样晶界被腐蚀,轰击后试样表面存在约为2μm的重熔层,腐蚀程度减轻,晶界处出现颗粒状碳化物；从EBSD结果可知,轰击5次试样晶粒尺寸最小,轰击5次和10次试样晶粒取向性更好,多为[101]和[110]。实验表明强流脉冲电子束轰击能够使哈氏合金X表面出现重熔层,并改变其晶粒大小和晶体取向。     

镍基耐蚀Hastelloy G3合金的组织特征及热力学计算

利用Thermo-Calc软件对镍基耐蚀Hastelloy G3合金进行了热力学计算，系统研究了成分对平衡相析出的影响规律，并通过SEM和TEM对合金时效处理后的析出相进行了观察。结果表明，合金析出的平衡相主要为σ相、μ相、M6C和M23C6；Cr、Mo含量主要影响σ相和μ相析出量及开始析出温度；而C元素显著影响碳化物M6C和M23C6的析出行为；进一步通过试验研究了时效过程中析出相的析出规律。     

Creep Properties of Base Metal and Welded Joint of Hastelloy XR Produced for High-Temperature Engineering Test Reactor in Simulated Primary-Coolant Helium

Creep tests of base metal, weld metal and welded joint of Hastelloy XR, which had the same chemical composition as Hastelloy XR produced for an intermediate heat exchanger of the High-Temperature Engineering Test Reactor, were conducted in simulated primary coolant helium. The weld metal and welded joint showed almost equal to or longer rupture time than the base metal of Hastelloy XR at 850 and 900°C, although they gave shorter rupture time at 950° C under low stress and at 1,000°C. The welded joint of Hastelloy XR ruptured at the base metal region at 850 and 900°C. On the other hand, it ruptured at the weld metal region at 950 and 1,000°C. The steady-state creep rate of weld metal of Hastelloy XR was lower than that of base metal at 850, 900 and 950°C. The creep rupture strengths of base metal, weld metal and welded joint of Hastelloy XR obtained in this study were confirmed to be much higher than the design allowable creep-rupture stress (S_R ) of the Design Allowable Limits below 950°C.     

On direct laser deposited Hastelloy X: dimension,surface finish,microstructure and mechanical properties

Abstract

For the first time, the influence of laser power, scan speed, scan spacing and nominal laser power density on the tensile properties, dimensional accuracy, surface roughness, number of cracks and top surface concavity of samples of Hastelloy X manufactured using a laser powder bed facility, has been assessed systematically on three-dimensional samples. It has been found that the nominal laser power density is the dominant factor, but the influence of scan spacing and scan speed can sometimes be significant. Density of >99·5% can be obtained using most conditions. Cracks are observed at corners of the samples. An optimised process window can be derived from the above systematic analysis under which the component can be built smoothly, with good surface finish and dimensional accuracy, consistent mechanical properties and the properties are comparable with those of forged products.     

少量硝酸对316L和Hastelloy C合金在循环废酸中腐蚀机理的影响

利用电化学方法、SEM和EDS研究了少量硝酸对316L和Hastelloy C合金在循环废酸中腐蚀机理的影响。结果表明,循环废酸中的少量硝酸能使温度为80℃的循环废酸具有强氧化性,使铁基奥氏体不锈钢316L在循环废酸中形成致密的钝化膜,使其腐蚀速率大幅度降低;使Hastelloy C合金在循环废酸中的钝化膜发生局部溶解,使其腐蚀速率增加。     

哈氏合金(Hastelloy C-276)管道的焊接

为满足丙烯酸及脂(AA/AE)工程中的哈氏合金(Hastelloy C-276)管线对接接头在强腐蚀性介质中的工作条件,采用GTAW焊接方法,对该材料进行了焊接工艺研究.在分析焊接性和反复试验的基础上,拟定了合理的焊接材料、焊接方法、焊接工艺参数以及焊接过程中的操作技巧和操作要点,按照标准JB4708对焊接接头进行多项...     

Hastelloy N合金表面激光熔覆NiCoCrAlY涂层在LiF-NaF-KF熔盐中的腐蚀行为研究

采用激光熔覆同步送粉技术在HastelloyN合金表面制备了NiCoCrAlY涂层,研究了HastelloyN基材和含NiCoCrAlY涂层的HastelloyN试样在900℃LiF-NaF-KF熔盐中的腐蚀行为。利用失重腐蚀法评估了试样的耐熔盐腐蚀能力,采用XRD和SEM表征了基材和涂层的物相组成、显微组织和腐蚀形貌,并结合EDS分析了微区成分。结果表明,NiCoCrAlY涂层试样的腐蚀速率仅为Hastelloy N基材的2/3。Hastelloy N基材表现为晶间腐蚀,其中Cr元素沿晶界发生选择性脱溶腐蚀,腐蚀前由γ-Ni和M_6C(M为Ni、Co、Cr等)等物相组成,腐蚀后新析出Co_9Mo_(21)Ni_(20)相。NiCoCrAlY涂层表现为均匀腐蚀,其中Al元素充当"消耗品"由涂层均匀向外扩散,形成的腐蚀产物可阻碍涂层中其它元素的扩散从而保护基材,腐蚀前主要由γ-Ni、Al_(0.983)Cr_(0.017)、AlNi_3等物相组成,腐蚀后只存在γ-Ni相。NiCoCrAlY涂层显著提高了基材的耐熔盐腐蚀性能。     

Microstructural evolution in nickel alloy C-276 after Ar ion irradiation

Irradiation damage in nickel alloy C-276 irradiated by 115 keV argon ions at room temperature with irradiation doses from 0.28 to 82.5 dpa has been investigated by transmission electron microscopy. Nano-scale black spot damage appeared at a dose higher than 0.83 dpa. Large interstitial-type dislocation loops were observed at the dose of 8.25 dpa. Both the density of dislocation loops and the density of network dislocations grew significantly with the increase of irradiation dose. However, the density of network dislocations declined at the dose of 27.5 dpa. But the total of dislocation density (density of dislocation lines plus density of dislocation loops) kept increasing and no signs of saturation were seen in the dose range explored. The results showed that the nickel alloy C-276 had good performance in delaying the development of black spots, dislocations and dislocation loops. However, original grains have formed into subgrains at the dose of 82.5 dpa, meaning that the grains in C-276 lost its structural integrity at doses higher than 82.5 dpa.