热处理过程中690合金热轧棒材显微组织演变

采用不同热处理工艺对热轧态690合金棒材进行处理,研究了合金的晶粒长大倾向,分析了晶粒尺寸对碳化物析出及晶界区域化学成分演变的影响。结果表明:690合金晶粒尺寸均随着固溶温度升高而增大。TT处理对合金晶粒尺寸的影响不明显。晶粒尺寸较大的690合金晶界碳化物较为连续,碳化物粗大、间距小、呈细条状,晶内含有少量的颗粒状碳化物;细小晶粒的合金晶界碳化物尺寸细小、间距大、呈颗粒状,晶粒内碳化物数量增加。随碳化物沿晶界析出,晶界区域Cr、Ni和Fe含量发生变化。与大晶粒尺寸的合金相比,小晶粒的690合金晶界最低Cr浓度增加,贫Cr区宽度明显减小。     

690合金的显微组织研究

应用透射电子显微镜（TEM）研究了690合金经固溶热处理,及经不同温度（600－800℃）和不同时间（0．5－200h)时效热处理后的显微组织,结果表明：690合金经过固溶处理及时效热处理后,在晶界上析出面心立方结构的碳化物M23C6;碳化物优先在晶界位错缠结后成核。在大角度晶界处,一偶晶粒的（100）晶面与界面接近平行时碳化物更容易析出;晶界上析出的碳化物总量与同一侧的基体有立方－立方的共格取向关系;碳化物不在孪 晶面上析出,但会在孪晶端头的非共格界面上析出,析出后沿＜110＞生长较快,形成针状;通过特殊热处理可以控制和调节晶界面碳化物的长大和贫Cr区中的Cr 含量,以获得最佳耐腐蚀性能。     

镍基690合金中晶界碳化物析出的研究

利用HRTEM,SEM和EBSD技术研究了固溶处理后镍基690合金在715℃时效时晶界处析出碳化物的形貌及与基体的取向关系.结果表明,碳化物在晶界处于高指数晶体学面的一侧晶粒中析出,并与此侧晶粒具有共格的取向关系.但是碳化物会向无共格取向关系一侧晶粒生长更快一些,碳化物向两侧晶粒生长速度的不同导致晶界附近Cr浓度曲线不对称,并且使晶界附近两侧晶粒的耐腐蚀能力不同.     

热处理对Inconel690合金晶粒变化和晶界析出物的影响

研究Inconel690合金在不同的热处理条件下晶粒大小和晶界析出物.结果表明:当固溶处理温度低于1100℃时,晶粒尺寸变化不大,当温度超过1150℃时,晶粒开始显著长大,建议固溶处理应在1100℃以下.Incone1690合金经固溶处理和特殊热处理(TT处理)后,晶界的主要析出物和沉淀物为Ti(C,N)和M23C6,析出物尺寸随热处理温度的升高而增大,分布的形态主要呈断续和半连续状.     

添加N对Inconel 690合金显微组织和晶界微区成分的影响

采用SEM和TEM研究了4种不同N含量的Inconel 690合金经1080℃、10 min固溶及715℃热处理后的显微组织演变和晶界微区元素分布,同时测量了合金的层错几率和晶间腐蚀速率。结果表明,相同热处理后,不同N含量Inconel 690合金的晶界M23C6碳化物析出形貌和晶界Cr贫化存在明显差异。随N含量增加,碳化物数量减少,晶界碳化物由连续分布转变为半连续分布,继而转变为离散分布。随N含量增加,Inconel 690合金层错几率先增加,在N含量为100×10~(-6)时达到最大值,随后层错几率降低。此外,N的加入缓解了晶界Cr贫化,提高了合金抗晶间腐蚀能力;但过高N含量导致较多氮化物夹杂。综合考虑,N含量在100×10~(-6)较为适宜。     

固溶处理对超超临界电站用镍基耐热合金组织及性能的影响

通过提高Inconel 617合金Al和Ti含量、增加B元素,获得一种超超临界电站用镍基耐热合金,研究固溶处理对合金组织及性能的影响。结果表明:1100~1190 ℃固溶2 h,随固溶温度提高,平均晶粒尺寸从68 μm长大至139 μm,硬度从203 HBW降至175 HBW;1100 ℃固溶1~4 h,晶内碳化物逐渐回溶,晶界碳化物沿晶界断续状分布且变化不明显。固溶温度提高,合金高温拉伸、室温冲击性能降低;炉冷试样高温拉伸性能略低于水冷试样,但显著高于Inconel 617合金。推荐试验合金固溶热处理工艺为1100 ℃×2 h水冷。     

固溶温度对改型In617合金组织和性能的影响

通过光学显微镜(OM)、扫描电镜(SEM)表征、EDS分析以及力学性能测试等方法研究了固溶温度对改型Inconel617(In617)合金组织和性能的影响。结果表明,改型In617合金在950~1200 ℃固溶2.5 h,平均晶粒尺寸从18 μm增长至183 μm;并建立了改型In617合金在950~1200 ℃固溶处理过程中的晶粒长大动力学模型。当固溶温度为1000 ℃时,晶界处M₂₃C₆碳化物回溶;超过1100 ℃固溶时,M₆C碳化物也基本回溶完毕,合金中仅存大尺寸MC型碳化物。随着固溶温度升高,混晶现象发生,合金高温强度逐渐降低,主要归因于碳化物的逐步回溶。其中在1050 ℃固溶时,由于晶界碳化物没有回溶完毕,所以此时改型In617合金的强度下降幅度不高,而当固溶温度达到1200 ℃时,晶界处碳化物消失,晶粒已经长大,导致合金强度大幅降低。     

热轧态Inconel625合金热处理后的组织及硬度

利用金相显微镜、扫描电镜、透射电镜和硬度仪研究了经960~1040℃固溶处理、700~900℃短时时效处理Inconel 625合金的微观组织和硬度。结果表明:随着固溶温度升高,晶粒尺寸逐渐增大,合金的硬度逐渐降低;固溶态的合金中存在较多富含Nb、Ti一次相颗粒;经700~900℃×50 h时效,晶界处的析出相主要是M_6C碳化物;在900℃×50 h时效的合金中晶界处发现了M_6C碳化物孪晶;在800℃×50 h时效态合金中,晶界附近有大量与晶界垂直的棒状第二相,晶粒内部有尺寸较小Ti的碳化物颗粒。     

690合金管冷轧及退火处理过程中的组织演变

利用光学金相显微镜和扫描电子显微镜研究了690合金一次冷轧管在中间退火过程中的组织演变规律,以及不同固溶处理制度对690合金二次冷轧管（成品尺寸管）的晶粒度和碳化物回溶行为的影响,并建立了退火过程中再结晶晶粒长大方程。试验结果表明：一次冷轧管中间退火最优工艺是1100℃/5 min,所建立的晶粒长大模型预测结果与实验值吻合很好,成品管经1100℃/3 min固溶后,平均晶粒尺寸在23.5μm左右,晶粒组织均匀,碳化物完全溶解。     

TT处理对690合金微观组织结构的影响

采用扫描电子显微镜(SEM)、背散射电子衍射分析技术(EBSD)研究了TT处理对690合金微观组织结构的影响。研究表明:TT处理不仅可以控制晶界碳化物的析出,还可以影响织构的方向和程度。690合金在715℃TT处理10h能够获得致密连续的晶界碳化物。TT处理前690合金在2个方向上存在密排,而在TT处理后密排只存在1个{111}方向。TT处理对低ΣCSL(coincidence site lattice)晶界的比例基本没有影响。TT处理对织构方向的影响可能会在690合金的抗应力腐蚀性能表现出来。     

晶粒度对Inconel 690合金微动磨损行为的影响

为预防及减缓微动损伤对核反应堆蒸汽发生器传热管的危害,深入研究了晶粒尺寸对Inconel 690合金微动磨损行为的影响。采用微动磨损试验方法对Inconel 690合金的微动磨损特性展开研究,并利用光学显微镜(OM)、维氏硬度计、扫描电镜(SEM)、能谱仪(EDS)和激光共焦扫描显微镜(LSCM)等对不同固溶温度下材料的微观组织结构、硬度和磨痕特征进行观察和分析。结果表明,随着固溶温度的升高,Inconel 690合金晶粒尺寸增大,硬度降低;在完全滑移区,摩擦因数随晶粒度和硬度的变化很小,其值均约为0.48;当Inconel 690合金平均晶粒尺寸为112μm,且SS304与Inconel 690合金硬度比为260∶176.4时,Inconel 690合金磨损体积最少;不同晶粒度和硬度下Inconel 690合金的微动磨损机制主要为剥层磨损、磨粒磨损和粘着磨损。     

晶粒度对690合金热变形特性的影响

利用物理模拟实验方法对具有不同晶粒尺寸的690合金试样进行热压缩变形实验,变形温度范围为1100～1200℃,应变速率分别为0.1,1,10s-1,获得了合金的流变应力数据,并对合金变形后的组织特征进行了分析,建立了包含初始晶粒度参数的本构关系模型。结果表明:晶粒尺寸增大使690合金高温变形时的流变应力增加,发生动态再结晶的临界应变增大,动态再结晶体积分数减小,根据所建立的流变应力本构模型计算出的流变应力值与实验值相近,从而完善了690合金的热变形本构方程。     

Effect of microstructure on stress corrosion cracking of alloy 600 and alloy 690 in 40% NaOH

Stress corrosion cracking (SCC) behaviors of Alloy 600, Alloy 690 and the Ni-10Cr-10Fe alloy have been studied using a C-ring in 40% NaOH solution at 315°C. The current density of Alloy 690 in polarization curves was higher at 200 mV above corrosion potential than that of Alloy 600. SCC resistance increased with Cr content for the chromium carbide free alloys, probably due to facilitation of SCC crack tip blunting with an increase in Cr content. Both thermally treated Alloy 600 and sensitized Alloy 600 have a comparable amount of intergranular carbide. But the former is more resistant to SCC than the latter, which might be attributed to the presence of the slight Cr depletion around the grain boundary in the former one. Sensitized Alloy 600 showed higher SCC resistance than the solution annealed one due to intergranular carbide in sensitized Alloy 600. This implies that the beneficial effect of intergranular carbide overrides the harmful effects of Cr depletion for sensitized Alloy 600. SCC resistance of Alloy 600 increased with grain size. This article based on a presentation made in the symposium “The 4th International Conference on Fracture and Strength of Solid”, held at POSTECH, Pohang, Korea, August 16–18 under the auspices of Far East and Ocean Fracture Society (FEOFS),et al.     

固溶热处理对GH3535合金组织和性能的影响

对热轧态GH3535合金进行不同温度和时间的固溶处理,采用扫描电子显微镜(SEM)、电子背散射衍射技术(EBSD)和拉伸试验等手段研究了固溶热处理后的合金组织及其对力学性能的影响。经过1177℃,20 min固溶热处理后,合金发生再结晶与晶粒长大,一次M_6C碳化物发生部分溶解。在更高温度下(1220和1260℃)固溶热处理后,晶粒异常长大且一次M_6C碳化物数量明显减少。随着固溶温度的提高和固溶时间的延长,合金的抗拉强度随之降低,而延伸率提高。通过组织分析发现,不同固溶热处理后合金的拉伸性能的变化源于晶粒的长大和一次M_6C碳化物的溶解。     

The Microstructural Evolution of Inconel Alloy 740 During Solution Treatment, Aging, and Exposure at 760?°C

In this study, the microstructural evolution of Inconel alloy 740 during solution treatment and aging was characterized using optical and scanning electron microscopy. During double solution heat treatment, carbon is liberated from the dissolution of MC carbides during the first solution treatment at 1150 °C, and fine MC carbides are precipitated on gamma grain boundaries during the second solution treatment at 1120 °C. Due to the concurrent decrease in carbon solubility and the increase in the contribution of grain boundary diffusion at lower temperatures, the MC carbides on the gamma grain boundaries provide a localized carbon reservoir that aids in M₂₃C₆ carbide precipitation on gamma grain boundaries during exposure at 760 °C. The γ′ phase, which is the key strengthening phase in alloy 740, is incorporated into the alloy microstructure during aging at 850 °C. The main source of microstructural instability observed during exposure at 760 °C was the coarsening of the γ′ phase.     

C-ring stress corrosion test for Inconel 600 and Inconel 690 sleeve joint welded by Nd:YAG laser

C-ring stress corrosion test for Inconel 600 and Inconel 690 sleeve joint welded by Nd:YAG laser were carried out to evaluate the applicability of the technique in the repair of heat exchanger tube of nuclear power plant. Corrosion test were carried out mainly in caustic solution. The applied stresses range between 207 and 414 MPa at 348 °C and the corrosion time is between 1624 and 4877 h. The experiment also has been done in primary water with one condition (379 MPa, 2931 h), and in sulphate solution with one condition (414 MPa, 1624 h). Stress corrosion cracking (SCC) was observed in the welded specimens immersed in sulphate and caustic solution but SCC was not observed in primary water. The length of SCC is related to corrosion time and applied stress. The length of SCC increases linearly with increasing corrosion time. SCC propagates as intergranular from base metal towards the weld of Inconel 690. Weld part of Inconel 690 appears to posses better resistance to SCC than base metal of Inconel 690 in caustic environment.     

Caustic stress corrosion cracking of alloys 600 and 690 with NaOH concentrations

In order to evaluate the stress corrosion cracking resistance for commercial alloys (C600MA, C600TT, C690TT) and Korean-made alloys (K600MA, K690TT), C-ring tests were performed in a caustic environment of 4, 10, 20, 30, and 50% NaOH solution at 315°C, for 480 h with an applied potential of 125 mV vs. OCP. Different stress corrosion cracking phenomena were observed according to the NaOH concentration. The rate of caustic IGSCC attack did not appear to increase monotonically with caustic concentrations, but peaked at a concentration between 4 and 50% caustic, or approximately 30% NaOH. Intergranular stress corrosion cracking was found for C600MA in 10, 20, and 30% NaOH solutions, while no cracking was observed in the 4 and 50% NaOH solutions. In 30% NaOH solution, transgrnular stress corrosion cracking was detected in C690TT, which may be related with the large amount of plastic strain (150% yield) and the applied potential (125 mV vs. OCP). The overall data clearly indicate that C600MA has the worst SCC resistance while K690TT offers the best resistance. There is also fairly good correlation between the caustic SCC susceptibility and some metallurgical parameters, particularly the grain size and the yield strength at room temperature. Specifically, materials having larger grain size and lower yield strength exhibited higher caustic SCC resistance.     

热连轧GH4169合金的晶粒长大行为

对热连轧(HCR)GH4169合金在固溶处理过程中晶粒长大行为进行系统研究。结果表明,该合金?相溶解温度在990～1000℃之间,δ相对晶粒长大有显著阻碍作用,在低于δ相溶解温度进行固溶处理时,析出的δ相使得晶粒长大缓慢;在高于δ相溶解温度以上时,晶粒随温度的升高快速长大。晶粒长大动力学表明:在高于δ相固溶线温度以上进行固溶处理时,晶粒生长指数随着固溶温度的升高而增加;固溶处理温度为1000和1050℃时的晶粒长大激活能为223.849kJ/mol,晶粒长大机制为自扩散过程控制机制,并建立了相应的晶粒长大动力学方程。     

Nb对690镍合金焊条熔敷金属DDC敏感性影响

采用应变开裂试验研究了Nb对Inconel 690焊条熔敷金属失塑裂纹敏感性的影响.结果表明,Nb在熔敷金属中主要以碳化物的形式存在于晶界上,起到了阻碍晶界滑移的作用,降低了材料DDC敏感性,但是当含量超过一定值以后,出现了局部液化现象,其最佳含量为1.73%.     

Corrosion of Inconel 690 and Inconel 693 in an iron phosphate glass melt

The isothermal corrosion behavior between 1000 °C and 1190 °C of Inconel 690 and 693 in an iron phosphate glass melt containing 26 wt.% of a simulated Hanford low activity nuclear waste (LAW) was investigated. At least three distinct corrosion processes were recognized for both alloys over different temperature ranges. Inconel 690 and 693 both display the best corrosion resistance at an intermediate temperature range (Inconel 690: 1050–1100 °C; Inconel 693: 1050–1165 °C), and more severe corrosion at both lower and higher temperatures. In general, Inconel 693 is less reactive over a wider temperature range than Inconel 690.