Critical Assessment 21: oxygen-assisted fatigue crack propagation in turbine disc superalloys

Ni-based superalloys in turbine disc applications face increasing susceptibility to oxygen-assisted fatigue crack propagation due to increased turbine entry temperatures. The continued lack of understanding of the interplay between the factors operating during oxygen-assisted fatigue crack propagation limits: (1) development of lifing methodologies to accurately predict the fatigue performance of disc alloys/components and (2) associated disc alloy developments. An underpinning requirement to better understand the role of oxygen is to characterise the process of oxygen diffusion in the localised stress/strain state at the crack tip, which is related closely to microstructural features. The link between three-dimensional crack tomography, crack propagation rate and oxygen-related attack needs to be established. Quantitative models which include the interaction between fatigue–creep–oxygen attack need further development.     

Microstructure and Transformation Behavior of in-situ Shape Memory Alloys by Selective Laser Melting Ti-Ni Mixed Powder

The selective laser melting(SLM) of Ti-Ni mixed powder with atomic ratio of 1:1 was performed in the present work in order to elaborate shape memory alloy(SMA).The martensite phase of Ti-Ni alloy can be found by X-ray diffraction(XRD) analysis under temperature field,moreover,the Ti2Ni phase at a high scanning velocity.The crystalline phase images also show that the synthesized Ti-Ni alloy possessed a refined martensite microstructure.In order to evaluate the mechanical properties,the microhardness and porosity were measured.The microhardness is relatively high about 400HV0.2 with champ temperature.Besides,the porosity is quite low due to the excellent laser energy absorptivity and meltability of Ni element.The differential scanning calorimetry(DSC) analysis shows that the transformation temperature from austenite phase to martensite phase is relatively high and stable.     

油脂加氢镍基纳米催化剂的研究

以纳米碳酸钙为载体,采用沉淀法制备了镍基纳米催化剂,以棕榈油的加氢为探针表征其活性。分析了制备方法、负载量、焙烧温度、还原温度及促进剂对催化剂活性的影响。研究结果显示:以纳米碳酸钙为载体,在镍负载量为30%左右、添加铝(镍与铝原子摩尔比6∶1)或钴(镍与钴原子摩尔比600∶1)为促进剂、焙烧温度350℃、还原温度400℃时,采用沉淀法制备的催化剂活性最高,可使氢化后的棕榈油碘值(I)降到0.5 g/100 g以下(催化剂用量占棕榈油质量的0.07%),表明该催化剂的催化性能可达工业要求水平。此外,采用相对廉价的纳米碳酸钙作载体,镍为主要活性组分,操作步骤简单,催化剂性能稳定,活性较高,经济效益好,具有较好的应用前景。     

FCC废催化剂镍脱除试验研究

针对含镍的FCC废催化剂(催化裂化催化剂),采用酸浸、焙烧-酸浸、氨浸、还原焙烧-氨浸、氯化焙烧工艺进行镍脱除试验,镍脱除率分别为16.64%、10%、0.8%、23.92%和64.53%,渣含镍＞0.1%,无法达到一般工业固废标准。然后采用还原熔炼工艺处理FCC废催化剂,当氧化铁添加量11%、煤粉添加量5%、熔炼温度1450℃、保温时间2h时,镍脱除率达到92.6%,熔炼渣含镍0.06%,达到一般工业固废标准。     

Na2SO4- and NaCl-Induced hot corrosion of six nickel-base superalloys

The short-time hot-corrosion behavior of six industrial nickel-base superalloys was investigated with static deposits of Na₂SO₄ or NaCl or both in still air. The oxidation kinetics and scale morphologies were measured with traditional laboratory techniques-thermobalance, metallography, electron microprobe, and x-ray analyses. Susceptibility to hot corrosion was found to be correlated to the type of scale produced during simple oxidation. Alloys forming an A1₂O₃ scale were found to be susceptible to Na₂SO₄ deposits, independent of their chromium content. The quantity of Na₂SO₄ deposit dictated the nature of the attack and, under certain conditions, the refractory element alloy additions appeared to play an essential role. Alloys containing Cr₂O₃ or TiO₂ in the simple oxidation scale proved to be sensitive to NaCl attack. Again, the severity of the attack within the susceptible alloy group was not related to the chromium or titanium content. Although less intensive than the Na₂SO₄ -induced hot corrosion, NaCl contaminations provoked extensive spalling. All of the hotcorrosion types encountered in this study were interpreted in the light of existing theories.Supported by the Délégation Générale à la Recherche Scientifique et Technique.     

负载型非晶态Ni-B/SiO2合金对芥酸加氢催化性能研究

研究了负载型非晶态Ni B/SiO2 合金催化剂对芥酸加氢制备山嵛酸的催化性能。结果表明 ,Ni B/SiO2 对芥酸加氢具有很高的活性 ,且稳定性较高 ,其催化性能优于非负载Ni B非晶态合金和RaneyNi催化剂。     

碳羟磷灰石的制备及其吸附镍离子的动力学研究

研究了碳羟磷灰石(CHAP)对Ni2+的吸附性能。从pH值、吸附时间及初始Ni2+浓度三方面对吸附能力的影响进行吸附试验。试验结果表明,在常温常压,CHAP吸附Ni2+的最佳pH值为6,最佳吸附时间为60 min,吸附量达到35.48 mg/g。CHAP对Ni2+的吸附过程符合准二级反应动力学模型。CHAP吸附Ni2+的能力随着废水中Ni2+浓度增加而增加,最大吸附量为38.8 mg/g,CHAP对Ni2+的吸附符合Langmuir吸附等温式。     

07Mn2Ni2Mo焊丝在线退火工艺探讨

介绍07Mn2Ni2Mo焊丝在线退火优化工艺。实验内容:(1)在750℃退火温度下,焊丝以2,4,6,8,10 m/min的运行速度进行退火实验;(2)焊丝采用4 m/min的运行速度,选择600,650,700,750,820,900℃进行退火实验。总结出优化退火工艺:退火温度为750℃,焊丝运行速度为4 m/min。退火后焊丝组织为铁素体+细小珠光体,组织已经完全再结晶,塑性指标得到恢复。     

涤纶织物化学镀Ni-Cu-P的反应动力学方程

研究了涤纶织物化学镀Ni-Cu-P过程镀液中各组分,pH,温度对合金沉积速率的影响,确定了化学镀Ni-Cu-P沉积反应的活化能,反应级数,速率常数以及动力学方程式。     

无钴马氏体时效钢电子束焊接接头组织与性能分析

对18Ni无Co马氏体时效钢进行了真空电子束焊接,用金相显微镜观察了焊接接头的组织形貌,并测定了焊缝区、热影响区、基体的显微硬度.结果表明,18Ni无Co马氏体时效钢组织为板条马氏体组织,材料焊接性能良好,焊缝区凝固组织为胞状树枝晶,熔合线附近热影响区晶粒发生了再结晶,晶粒长大明显.硬度分布有明显的规律性,焊缝区硬度最低,细晶区硬度最高,熔合线附近的热影响区,离熔合线越远,硬度值越高.在距熔合线2.5 mm处有一个马氏体与奥氏体两相混合的狭窄区域,硬度较其两侧有明显降低.