航空难加工材料切削刀具磨损与剩余寿命预测研究进展

航空制造领域因轻量化、强度等特殊的应用需求,大量使用钛合金、镍基合金等难切削材料,刀具磨损速率快,刀具过度磨损会影响产品质量,在保证产品质量的前提下,为了充分发挥刀具使用价值,亟需监测刀具磨损状态和预测刀具剩余寿命。针对刀具剩余寿命预测的定义、分类和主要预测方法进行了阐述,同时,刀具磨损监测作为刀具寿命预测的基础和先决条件,简述了其重要的流程和常见模型。刀具剩余寿命预测模型主要包括基于物理模型的预测、基于数据驱动的预测和混合预测三大类,对不同预测方法的优缺点和适用场景进行总结,并讨论了刀具剩余寿命预测的未来研究方向。     

A modern and robust methodology for modeling anisotropic creep characteristics of Ni-based DS and SC superalloys

According to more recent work,the Wilshire equations have shown good prediction accuracy in a wide range of materials and stress-temperature conditions,particularly in extrapolation of short term results to long term predictions.In the current paper,this methodology was further developed for modeling anisotropic creep characteristics(i.e.minimum creep strain εmin ,stress rupture life tf and time to a specified strain tε)of four typical Ni-based directionally solidified(DS)and single crystal(SC)superalloys,where a simple orientation factor related to the ultimate tensile strength(UTS)was introduced.The application of these simplistic approaches showed that the anisotropic creep characteristics in a wide range of stress-temperature conditions can be accurately simulated.Meanwhile,during the application of the modified Wilshire equations,break points occurring at the specified stress levels agree well with the transition of creep deformation mechanisms occurring in different stress regions,which provides confidence for using this method.     

Copolymerization of norbornene with norbornene terminated polystyrene macromonomer in the presence of Ni-based/MAO catalytic systems

Copolymerization of -norbornenyl polystyrene macromonomer (NBE-PS) with norbornene (NBE) using Ni-based catalysts in combination with methylaluminoxane (MAO) was investigated. The nature of the catalyst, the of the polystyrene macromonomer as well as the [NBE-PS]/[NBE] ratio have been shown to be important parameters to obtain graft copolymers with high NBE-PS incorporation (up to 43 wt%). The compatibilization ability of these graft copolymers has been checked for PS/PNBE blends. The length of the grafts was proved not to be an important parameter to consider compatibilization of the PS/PNBE blend.     

Effects of returns on composition,microstructure and mechanical properties of GH4169 superalloy

To recycle the returned alloy effectively, effects of returns proportion on alloy composition, microstructure and compression properties of superalloy GH4169 were studied by means of scanning electron microscopy(SEM), energy dispersive spectroscopy(EDS) and thermal-mechanical simulator. The results show that returns addition has no significant effect on the main alloy elements content and the principle precipitates, but increases the volume fraction of Al_2O_3 inclusions, resulting in the increase of oxygen level of GH4169 alloy. Returns addition does not change the elastic and plastic deformation process at room temperature or at 1,150 °C, but high returns proportion GH4169 alloy shows improved compression strength and yield strength. The alloy with 100% returns shows a maximum compression strength 1,153.45 MPa at room temperature, while the alloy with 80% returns has a maximum value 69.3 MPa at 1,150 °C. Returns addition increases fluctuation range and reduces the stability of yield strength and compression strength of GH4169 alloy at room temperature. It is noted that the volume fraction and the size of Al_2O_3, and the fraction of Laves phase reach their maximum values in the GH4169 alloy with 60% returns, which exhibits maximum yield strength of 516.65 MPa at room temperature and 62.17 MPa at 1,150 °C.     

High-Temperature Oxidation Behavior and Mechanism of a New Type of Wrought Ni–Fe–Cr–Al Superalloy up to 1300°C

The oxidation behavior of a new type of wrought Ni–Fe–Cr–Alsuperalloy has been investigated systematically in the temperature range of1100 to 1300°C. Results are compared with those of alloy 214, Inconel600, and GH 3030. It is shown that the oxidation resistance of the newsuperalloy is excellent and much better than that of the comparisonalloys. Scanning electron microscopy (SEM), electron probe microanalysis(EPMA), and X-ray diffraction (XRD) experiments reveal that the excellentoxidation resistance of the new superalloy is due to the formation of adense, stable and continuous Al₂O₃ and Cr₂O₃ oxide layer at hightemperatures. Differential thermal analysis (DTA) shows that the formationof Cr₂O₃ and Al₂O₃ oxide layers on the new superalloy reaches a maximum at1060 and 1356°C, respectively. The Cr2O3 layer peels off easily, and thesingle dense Al₂O₃ layer remains, giving good oxidation resistance attemperatures higher than 1150°C. In addition, the new superalloypossesses high mechanical strength at high temperatures. On-site testsshowed that the new superalloy has ideal oxidation resistance and can beused at high temperatures up to 1300°C in various oxidizing andcorrosion atmospheres, such as those containing SO₂, CO₂ etc., for longperiods.     

The Main Degradation Modes of an Aluminide Coating on a Co-Base Superalloy During High-Temperature Oxidation in Air

Degradation of aluminide coatings occurs by two ways, one by coating oxidation, and the other by interdiffusion of Al. In this paper, the structure variation and phase transformation are analyzed for the aluminide coating on a newly developed Co-base superalloy (DZ40M alloy) after oxidation at 900 and 1000°C in air. The results show that degradation of this coating was mainly by oxidation at 900°C, but principally by interdiffusion at 1000°C. The main degradation mode of the coating is primarily dependent on the oxidation temperature and the specific structure of the coating itself.     

热力耦合对一种第四代镍基单晶高温合金1100℃蠕变组织演变的影响

以一种第四代镍基单晶高温合金为研究对象,采用变截面蠕变试样,在1100℃、43~96 MPa条件下进行200 h蠕变中断实验,利用SEM和TEM观察了微观组织演变规律,利用同步辐射高能XRD和EPMA分析了高温低应力条件下镍基单晶高温合金的蠕变组织演变。结果表明:随着应力的增大,镍基单晶高温合金的γ′相体积分数降低,筏化程度增大且筏排厚度下降,同时,γ相通道宽度逐渐增大,而γ/γ’两相界面位错网间距逐渐减小。固溶强化元素Re、Mo和Cr等在γ相中的富集导致γ/γ’两相错配度绝对值增大。蠕变过程中γ’相体积分数降低和γ’相筏排厚度减小显著降低了合金的强度。另外,位错在γ′相溶解所导致的弯曲相界处的塞积,使位错易于切入γ′相,也是镍基单晶高温合金室温硬度下降的重要原因。     

Steam reforming of n-hexadecane over noble metal-modified Ni-based catalysts

Steam reforming of n-hexadecane, a main constituent of diesel, over noble metal-modified Ni-based hydrotalcite catalyst was carried out in a temperature range of 700–950 °C, at an atmospheric pressure with space velocity of 10,000–100,000 h⁻¹ and feed molar ratio of H₂O/C = 3.0. The catalysts were prepared by a co-precipitation and dipping methods. The noble metal-modified Ni-based hydrotalcite catalyst displayed higher resistance for the sintering of active metal than the Ni-based hydrotalcite catalyst prepared by the conventional method. It was found that the Rh-modified Ni-based catalysts showed high resistance to the formation of carbon compared to Ni-based catalysts. The results suggest that Rh-modified Ni-based catalyst can be applied for the steam reforming (SR) reaction of diesel.