Mass-spectrometric determination of activities in Fe−Cr and Fe−Cr−Ni alloys

The Knudsen cell-mass spectrometer combination has been used to study the Fe?Cr system and some Fe?Cr?Ni liquid alloys. The Fe?Cr liquid alloys at 1600°C are found to be essentially ideal when referred to pure liquids as standard states. Phase equilibria over a limited composition range for this system are derived from the behavior of the ion-current ratios. The necessary equations are derived to apply the integration technique to the measured ion current ratios in a ternary system and the method is applied to the Fe?Cr?Ni system at 1600°C. The results are represented, within experimental error, by the following equations: forN _Fe≥0.6, $$\begin{gathered} ln \gamma _{Fe} = - 0.08 N_{Ni}^2 \hfill \\ \ln \gamma _{Cr} = 0.09 - 0.08 N_{Ni}^2 \hfill \\ \ln \gamma _{Ni} = - 0.26 - 0.08(1 - N_{Ni} )^2 \hfill \\ \end{gathered} $$ forN _Fe=0.45, $$\begin{gathered} \ln \gamma _{Fe} = - 0.20 N_{Ni}^2 \hfill \\ \ln \gamma _{Cr} = 0.09 - 0.20 N_{Ni}^2 \hfill \\ \ln \gamma _{Ni} = - 0.19 - 0.20(1 - N_{Ni} )^2 \hfill \\ \end{gathered} $$      

Nitrogen solubility in complex liquid Fe−Cr−Ni alloys

Measurements of nitrogen solubility were performed in a series of liquid iron-chromium-nickel alloys near the composition of the commercial superalloy INCOLOY^* 800 (I:21 pct Cr, 33 pct Ni, bal. Fe). This work was carried out at 1450 to 1600°C and up to one atmosphere of nitrogen gas pressure. Sieverts' law was obeyed by nitrogen in all the alloys. Changes were observed in the compositions of all the melts studied, mainly due to the chromium loss by volatilization. These changes necessitated nitrogen solubility measurements in a series of alloys immediately surrounding alloy I. The experimental results have been prepared as a regression polynomial equation for the logarithm of nitrogen solubility as a function of temperature and reported weight percentages of chromium and nickel in the alloys. The standard Gibbs free energy of nitrogen solution in a region around alloy I is given as ΓG ^o=−58,700+48.20T Joules/g atom N. At 1600°C, the temperature coefficient of nitrogen solubility in I is −2.65×10⁻⁴ pct N/K. The shape of a portion, of the nitrogen solubility surface for the Fe−Cr−Ni system near to alloy I at 1600°C is defined.     

Alloy powders in the Fe—Cu, Fe—Cr, Fe—Mn, and Fe—Cr—Mn systems

Studies have been done on iron-copper, iron-chromium, iron-manganese, and iron-chromium-manganese powder alloys, which have been made by dispersing the melts with high-pressure nitrogen. The use of such alloys in the preparation of low-alloy construction materials eases the stringent specifications for the oxidation potential of the controlled gas medium, and it also produces a more uniform distribution of the alloying elements in the sintered material.     

油井管用铁镍基耐蚀合金研究

铁镍基合金作为一种综合耐蚀性能优良且成本低廉的耐蚀合金,在油气田的开采领域已得到了广泛的应用。针对目前在国内油井管材领域应用比较广泛的合金028、825以及G3,分析了析出相形成规律,总结该类耐蚀合金的冶炼、热加工和冷加工、机械性能、耐蚀性能和焊接性能等方面的研究进展。研究表明:有效控制第二相的析出,可以提高合金的耐蚀性能;在管材的生产工艺上要注意热加工以及冷加工过程中的加热温度、冷却速度以及变形温度和变形速率;合金的双极性钝化膜有效提高了材料在复杂服役环境下的抗局部腐蚀性能。     

The crystallography of the austenite-ferrite/carbide transformation in Fe−Cr−C alloys

This paper establishes the crystallography of the austenite-ferrite/carbide transformation in Cr bearing steels. The crystallographic analysis, based on the use of retained austenite in the martensitic phase, is consistent with the oriented nucleation of ferrite in austenite. Similarly, it is shown that the nature of the carbide dispersion, which precipitates in association with the transformation, is a sensitive function of the exact austenite/ferrite crystallography.     

Effect of titanium on the nitrogen solubility in complex liquid Fe−Cr−Ni alloys

The effects of dilute additions of titanium up to 0.20 wt pct on the solubility of nitrogen in two complex Fe−Cr−Ni alloys were examined over the temperature range 1450 to 1600°C. Sieverts' law was obeyed by all titanium-bearing alloys up to some nitrogen pressure below one atmosphere. ‘Breaks’ in each solubility plot were observed that corresponded to the formation of titanium nitride. Titanium additions were observed to lower the nitrogen solubility in each group of alloys. This effect is opposite to that previously observed in pure iron. Calculated values of the solubility product (pct Ti) (pct N) for TiN formation in each alloy increased with rising melt temperature.     

Corrosion in atmospheric fluidized bed combustors—The reactions of CaSO4 with Cr,Ni, Co,Fe, and several alloys

When coal is burned in the presence of limestone in an atmospheric fluidized-bed combustor (AFBC), the sulfur emission can be kept below acceptable EPA levels. Calcining of the limestone produces CaO, which then forms solid CaSO₄ by a reaction with the SO₂ produced during coal combustion. The internal components (e.g., heat exchanger tubes) of the bed, however, become coated with a compact layer of CaSO₄, CaO, and ash during combustion. It has been suggested that the presence of the sulfate on these hot metal surfaces is the cause of observed instances of accelerated oxidation-sulfidation. This paper presents results which support the above suggestion. The reactions between Cr, Ni, Co, Fe, alloy 800, 2.25 Cr-1 Mo, 9 Cr-1 Mo steels, or 304 stainless steel with CaSO₄ were studied using differential thermal and thermogravimetric analyses. The reaction products were analyzed using X-ray diffraction, optical microscopy, and in some instances, X-ray energy dispersive analyses. The chromium-calcium sulfate reaction is the only case studied in which a sulfide is not formed. In that case, CaCr₂O₄ is the reaction product. In all other cases, the reactions are oxidation-sulfidation processes.     

热处理对添加少量Cr、Fe的Ti-Ni合金组织和力学性能的影响

采用真空熔炼法制备Ti_(45)Ni_(55)Cr_(0.3)和Ti_(45)Ni_(52)Fe_3合金(元素含量为摩尔分数)铸锭,对其进行均匀化处理以及850℃/1 h固溶和水淬后,分别采用3种不同的工艺进行热处理:1)850℃/1 h固溶,2)375℃/1 h时效,3)25%冷轧+375℃/1 h退火,研究热处理工艺对合金的相变特性、力学性能、内耗性能和微观组织的影响。结果表明,Ti_(45)Ni_(55)Cr_(0.3)和Ti_(45)Ni_(52)Fe_3合金的基体均由B2与R相组成;Ti_(45)Ni_(55)Cr_(0.3)合金经过375℃/1 h时效或25%冷轧+375℃/1 h退火处理后,析出Cr3Ni2粒子,时效后抗拉强度为1 385 MPa,时效升温过程的峰值内耗达到0.53;Ti_(45)Ni_(52)Fe_3合金经过25%冷轧+375℃/1 h退火后析出Ti3Ni4相,抗拉强度为770 MPa;与其它热处理工艺的升温过程相比,Ti_(45)Ni_(52)Fe_3合金的时效升温过程峰值内耗最高,达到0.158;降温过程中,Ti_(45)Ni_(55)Cr_(0.3)合金在时效降温过程中发生B2→R→M相变,退火的降温过程中发生B2?R相变,而Ti_(45)Ni_(52)Fe_3合金在退火的降温过程中发生B2→R→M相变。     

The effect of chromium on the activity coefficient of sulfur in liquid Fe−Cr−S alloys

The effect of chromium on the activity coefficient of sulfur in the ternary system Fe−Cr−S has been determined in the temperature range 1525° to 1755°C for chromium concentrations of up to 40 wt pct, using a levitation melting technique in H₂−H₂S atmospheres. The first order free energy interaction coefficient,e _S ^Cr , which is derived on the assumption that the thermal diffusion error is constant for both binary Fe−S and ternary Fe−Cr−S melts under controlled levitation conditions, is given by the relationship:e _S ^Cr =−94.2/T+0.040 The first order enthalpy and entropy interaction coefficients are found to beh _S ^Cr =−430±70 ands _S ^Cr =−0.183±0.007 respectively. These results are in good agreement with recently published data.     

An experimental study of carbide-austenite equilibria in iron- base alloys with Mo,Cr, Ni,and Mn in the temperature range 1173 to 1373 K

The carbide/austenite equilibria were studied experimentally in the alloy systems Fe-Mo-Cr-C, Fe-Mo-Ni-C, Fe-Mo-Mn-C, Fe-Cr-Mn-C, Fe-Cr-Ni-C and Fe-Cr-Ni-Mn-C in the temperature range 1173 to 1373 K. The carbides were identified by microscopic examination after etching and by X-ray analysis of carbide residues obtained by electrolytic extraction. The alloy contents in the individual phases were measured with a microprobe technique. The partitioning of the alloying elements were evaluated and phase diagrams at constant temperature and carbon activity were constructed from the experimental information. Formerly Research Assistant at the Division of Physical Metallurgy, The Royal Institute of Technology, S-10044 Stockholm 70, Sweden     

氧化石墨烯改性质子交换膜燃料电池用炭纤维纸

以天然鳞片石墨为原料,采用改进Hummer法制备氧化石墨烯,与酚醛树脂直接共混配置均匀分散溶液。将炭纤维坯体浸渍其中,采用模压固化、热处理的工艺制备氧化石墨烯改性质子交换膜燃料电池用炭纤维纸。采用TEM,XRD,AFM和FTIR等测试技术研究氧化石墨烯的形貌和结构特征,用SEM,XRD和四探针电阻仪等测试手段表征炭纸的表面形貌、石墨化度和面电阻率。结果表明:随氧化石墨烯含量增大,炭纸的石墨化度提高,面电阻率降低,抗拉强度增大。当氧化石墨烯添加量为2%时,改性后炭纸的石墨化度达到70.8%,面电阻率降为2.42 m?/cm,抗拉强度为24.01 MPa。单电池测试电压为0.6 V时,炭纸GO2的电池电流密度达到1 450 m A/cm2。     

An investigation of grain-boundary embrittlement in Fe−P,Fe−P−S,and Fe−Sb−S alloys

Grain-boundary embrittlement of pure iron due to phosphorous, antimony and sulfur is studied using fracture appearance transition temperature measurements and Auger electron emission spectroscopy chemical analysis of fractured surfaces. Phosphorus and sulfur are found to segregate to grain boundaries in the entire ferrite range. Segregation to grain boundaries of these elements in the austenite appears to be negligible. It is shown that the segregation of these elements to grain boundaries in iron does not conform to the Gibb's equilibrium segregation model. Sulfur appears to be a more severe embrittler of iron than does phosphorous. P. V. RAMASUBRAMANIAN formerly was Graduate Research Assistant, University of Minnesota. D. F. STEIN, formerly Professor, Department of Mechanical and Chemical Engineering, University of Minnesota     

由粉末冶金Fe(Cr,Mo)钢制备的同步器齿毂的力学性能

试验测定零件本身的强度性能是困难的,因此通常不采用此类数据.本文介绍了一种用于直接测定零件本身强度性能的方法,即用水射流切割零件,随后进行磨加工制备小型矩形试棒(约40mm×5mm×5mm)测定数据.采用典型粉末冶金零件——粉末冶金高合金化Fe(Cr,Mo)钢同步器齿毂制备的小型试棒测定抗拉强度、冲击强度及3点弯曲横向断裂强度,并和常规拉伸试样(DIN EN ISO 2740)的强度与冲击性能进行了对比.结果表明,由同步器齿毂与常规试样测定的数据都在试验误差范围之内,完全一致.为了证实对比的有效性,还用全面的化学与显微组织分析证明了2种试样的相似性.最后,建立了小型拉伸试棒的横向断裂强度与抗拉强度之间的相关性.     

Electrochemical properties of cobalt-free La0.80Mg0.20Ni2.85Al0.11M0.53 （M=Ni, Si, Cr, Cu, Fe） alloys

In order to investigate the effect of different B-site additions on phase structure and electrochemical properties of cobalt-free La-Mg-Ni based alloys, La0.80Mg0.20Ni2.85Al0.11M0.53 (M=Ni, Si, Cr, Cu, Fe) hydrogen storage alloys were prepared and studied systemati-cally. X-ray powder diffraction showed that the alloys consisted mainly of LaNi3 phase and LaNi5 phase except that Cr addition caused a minor Cr phase. Electrochemical testing indicated that alloys with additional Ni, Cr, Cu or Fe were activated within only 1-2 cycles, while that with Si addition needed 4 cycles. Adding Si, Cu and Fe increased cycling stability of La-Mg-Ni based alloys. However, maximum discharge capacity decreased from 362 mAh/g to 215 mAh/g in the order of Ni>Fe>Cu>Cr>Si. In addition, electrochemical kinetics of alloy electrodes was also researched by measuring high rate discharge ability (HRD), hydrogen diffusion coefficient (D) and limiting current density (IL).     

Thermodynamic laws of the oxygen solubility in liquid metals (Ni,Co, Fe,Mn, Cr) and the formation of oxygen-containing solutions in the alloys based on them

The solubility of oxygen in liquid Ni, Co, Fe, Mn, and Cr metals (Group IV in the periodic table) has been found for the first time. Linear dependences of the oxygen solubility on the standard Gibbs energy for the oxidation reaction of a liquid metal with gaseous oxygen are found. The revealed function of oxygen solubility is of scientific importance and allows one to develop a theory of oxygen solutions in liquid metals and liquid multicomponent metallic compositions and to calculate the energies of mixing of liquid metals with oxygen from ΔG _MO ^° for metal oxidation reactions with allowance for pseudoregular-solution model equations. Using the energies of mixing and metal compositions, we calculated the equilibrium oxygen concentrations in a metal molten pool at the end of oxidation stage of melting 08Kh18N10T steel in an arc furnace. This fact indicates practical importance of the found function of the oxygen solubility in metals.