Oxidation behavior of Hastelloy C-2000 superalloy at 800 °C and 1000 °C

The oxidation behavior of Hastelloy C-2000 alloy was investigated in air at 800 °C and 1000 °C for 100 h, respectively. Oxidation kinetics and oxide scales morphologies were examined by mass gain measurement, scanning electron microscopy（SEM）, X-ray diffraction（XRD） and X-ray photoelectron spectroscopy（XPS）. The oxidation behavior of the alloy approximately follows a parabolic rate law. Moreover, annealing twins defect structure in matrix deteriorates the oxidation resistance of alloy due to the improvement of diffusion rates for alloying elements and oxygen atoms. At 800 °C, the microstructure is primarily composed of Ni O and Cr1.3Fe0.7O6 and the initial annealing twins structure is visible and Mo-rich phases are emerged to approach boundary of oxide scales. At 1000 °C, however, the morphology microstructure of oxide scales consists of oxide particle with fine Cr oxides and large Ni oxides by inlaying each other, whilst Mo-rich phases hardly appear closing to the interface of oxide scales.

Flow stress prediction of Hastelloy C-276 alloy using modified Zerilli−Armstrong,Johnson−Cook and Arrhenius-type constitutive models

To better understand the hot deformation behaviors of Hastelloy C-276 alloy under elevated temperatures,hot tensile tests were carried out in the temperature range of 1223−1423 K and the strain rate range of 0.01−10 s^−1,respectively.Based on the modified Zerilli−Armstrong,modified Johnson-Cook,and strain-compensated Arrheniustype models,three constitutive equations were established to describe the high-temperature flow stress of this alloy.Meanwhile,the predictability of the obtained models was evaluated by the calculation of correlation coefficients(r)and absolute errors(Δ),where the values of r for the modified Zerilli−Armstrong,Johnson−Cook,and Arrhenius-type constitutive models were computed to be 0.935,0.968 and 0.984,and the values ofΔwere calculated to be 13.4%,10.5%and 6.7%,respectively.Moreover,the experimental and predicted flow stresses were compared in the strain range of 0.1−0.5,the results further indicated that the obtained modified Arrhenius-type model possessed better predictability on hot flow behavior of Hastelloy C-276.

哈氏C-2000合金的耐腐蚀行为试验研究

试验研究了哈氏C-2000合金的晶间腐蚀、点腐蚀和应力腐蚀敏感行为,探讨了环境因素、应力因素和固溶热处理等对哈氏C-2000合金应力腐蚀开裂(SCC)行为的影响。结果表明,哈氏C-2000合金有很好的耐室温酸性NaC l水溶液全面腐蚀和应力腐蚀的性能。然而由于Mo元素的偏析使得该合金在硫酸和硫酸铁混合溶液中具有较高的晶间腐蚀敏感性,焊接接头在该环境中存在较明显的热影响区选择性腐蚀。喷丸形变强化和固溶处理能够明显提高该合金基材与焊接接头的抗全面腐蚀和应力腐蚀性能。

Elemental micro-segregation characteristic of fiber laser welded Hastelloy C-276 sheet

The elemental micro-segregation characteristic within the weld zone for ytterbium fiber laser welded Hastelloy C-276sheet was investigated. The analysis of segregation ratio and equilibrium distribution coefficient of elements, determined throughEDS data, indicate the reduction in micro-segregation of elements compared with the previous reported literatures for laser weldedHastelloy C-276. High melting efficiency of ytterbium fiber laser, reduction in the amount of linear heat input, and high cooling rateof the mushy zone lead to the reduction in micro-segregation. The melting efficiency of ytterbium fiber laser for welding of HastelloyC-276 of 64% is higher than that （48%） of conventional welding methods. High melting efficiency leads to the reduction in the linearheat input required for welding. Hence, in the present investigation, the same was found to substantially reduce as compared to theprevious reported literature. The cooling rate from liquidus temperature to solidus temperature at the weld centerline was found to bein the order of 10^3℃/s. Cellular dendritic substructure that constituted for lower micro-segregation was formed at the weldcenterline.

利用双层辉光等离子技术进行镍基耐蚀合金表面合金化的研究

研究了在 2 0钢和不锈钢基材上 ,利用双层辉光离子渗金属技术进行Ni Cr Mo Cu多元共渗表面合金化 ,采用电化学方法对两种基材表面形成的渗层在 5 %HCl中的腐蚀性能进行了测定。结果表明 :在两种基材上都能得到类似于源极HastelloyC - 2 0 0 0合金的表面合金渗层 ,在不锈钢表面上形成的渗层的耐蚀性能接近HastelloyC - 2 0 0 0合金并且优于Alloy 5 9合金 ,在 2

Continuous electropolishing technique for long-length Hastelloy C-276 tape

Preparation of the second-generation high-tem- perature superconducting tape by ion beam-assisted depo- sition （IBAD） requires a flat metal substrate. In this work, the electrochemical polishing of long-length Hastelloy C-276 alloy was studied, and its process parameters, characterized roughness and other properties were inves- tigated. A 10-meter-long Hastelloy C-276 alloy was pre- pared by electrochemical polishing. The following optimized processing parameters are obtained： temperature of 45 ℃, current density of 0.439 A.cm-2 and polishing time of 60 s. The average roughness value （Ra） of the surface is less than 5 nm （5 μm × 5 μm）, which was characterized by atomic force microscopy. This value sat- isfies the requirements for the further preparation of tran- sition-layer pair by the IBAD technology route.

关于哈氏C-2000合金SMAW方法的焊接工艺探讨

哈氏C-2000合金是哈氏家族"C"合金成员,是美国Haynes国际公司本世纪创新之作,属于Ni-Cr-Mo合金,UNS编号为:N06200。该材料在国内应用案例较少,通过研究、分析该材料的焊接性,选择SMAW(焊条电弧焊)的焊接方法,按NB/T47014进行焊接工艺评定,制定合理的焊接工艺及措施,对保证焊接质量,满足设备使用要求,推广该材料在压力容器上的应用具有一定的指导作用。