45#钢的NiCrBSi激光涂复

应用2 kW-OO 激光器在45#铜板上进行NiCrBSi合盘的激光涂复处理．使用透射电镜和X射线衍射进行分桁的结果表明整个激光区的相组成是相同的,而在熔化区与基体交界的过渡层的相组成则与熔化区的有所不同.     

镍基超合金的Nd-YAG激光熔敷涂层行为研究

对ЖС6y、К24、К17三种镍基超合金的几种材料的Nd—YAG激光熔敷涂层行为进行了试验研究,并与三种超合金激光重熔行为进行了对比。研究表明,三种镍基超合金的重熔性都很差,热裂纹敏感性高,重熔区出现很多凝固裂纹。几种粉末涂层行为不尽相同,但对超合金基材的裂纹敏感性都有程度不同的改善,大大减少甚至抑制了基村上裂纹的产生,并在其与基材的界面处形成一白亮的熔合区,达到冶金结合。采用某几种钴基合金和镍基合金粉末,可在某种超合金基材上获得高质量无裂纹涂层。     

Synchrotron Microbeam Diffraction Study of the Microstructure and the Chemical Composition in a Monocrystalline Ni-Base Turbine Blade After a Thermomechanical Mission Test

High-performance turbine blades composed of monocrystalline Ni-base / superalloys are often protected by coatings to resist the high-temperature corrosive atmosphere environment applications. During applications severe thermal and mechanical loads cause drastic and complicated changes in the microstructure and the chemical composition, also combined with strong lateral gradients of both temperature and stress. Microbeam X-ray diffraction experiments with a spatial resolution of about 5 m enabled the determination of both the microstructural and the chemical composition gradients within material volumes of the sizes of the order of about 1 mm³ or smaller. The high angular and spatial resolution was achieved by a special focusing technique using a Bragg–Fresnel focusing monochromator at the BM5 beamline of the ESRF synchrotron at Grenoble. The X-ray diffraction experiments were complemented and supported by electron microscopy investigations of the microstructure and the chemical composition.     

考虑运动硬化的DD3镍基合金力学行为研究

详细介绍了镍基合金的晶体塑性本构模型,在Asaro大变形晶体塑性框架下,详细介绍了镍基合金的晶体塑性本构模型,在Asaro大变形晶体塑性框架下,引入了运动硬化规律,考虑了温度和应变率对晶体塑性变形的影响,通过针对每个滑移系考虑屈服准则和流动规律建立了晶体塑性模型. 对积分过程进行了推导,通过编写ABAQUS材料用户子程序(UMAT), 实现本构模型的有限元积分算法. 在此基础上模拟了DD3镍基单晶合金在单轴拉伸和循环载荷下的响应,并与实验数据进行了对比. 利用该模型可以很好地模拟镍基单晶所具有的各向异性特性,体现了镍基单晶在循环载荷作用下的拉-压不对称性.      

Microstructure-sensitive extreme value probabilities for high cycle fatigue of Ni-base superalloy IN100

To quantify the effects of interactions between various microstructure attributes on fatigue life in the high cycle fatigue (HCF) regime, we have proposed a new microstructure-sensitive extreme value statistical framework. This framework couples the extreme value distributions of certain fatigue indicator parameters (FIPs) or response functions to the correlated microstructure attributes that exist at the extreme value locations of these FIPs. We demonstrate the application of this statistical framework to investigate the microstructure-sensitive fatigue response of the PM Ni-base superalloy IN100 at 650 °C. To accomplish this task, we construct statistical volume elements (SVEs) used to compute the local response for 200 instantiations of IN100. These SVEs are constructed and simulated via the finite element method with crystal plasticity constitutive relations. The results of the simulations are used to explore extreme value statistics of the FIPs for these microstructures. The extreme value distributions of the Fatemi–Socie FIP are fit with high confidence by the Gumbel distribution and are defined in a representative nature with as few as 25 simulated microstructure instantiations (i.e., SVEs). The extreme value marked correlation functions of the apparent Schmid factor based on the geometry of the slip systems relative to the loading direction indicate that cube slip may be important to fatigue crack formation in this material system. This supports previous experimental observations of fatigue crack formation and microstructurally small fatigue crack growth along cube planes in IN100 in grains that are unfavorably oriented for octahedral slip at elevated temperatures.     

Inconel 738激光熔覆层的裂纹控制方法

针对镍基高温合金激光熔覆过程中覆层极易产生裂纹的问题,在高温合金K438基体上激光熔覆Inconel 738合金粉,研究了熔覆层的开裂机理以及裂纹控制方法。裂纹由靠近基体端的过渡层产生并扩展到熔覆层,具有典型的沿晶特征,裂纹的形成主要与熔覆层中的热输入和低熔共晶相有关。从减少激光熔覆层中的低熔共晶相出发,通过优化激光熔覆工艺参数、添加适量Y2O3以及对基体进行同步冷却,可在一定程度上减少甚至避免熔覆层裂纹的产生。     

Gamma prime and TCP phases and mechanical properties of thermally exposed nickel-base superalloy

The effect of long-term thermal exposure and casting superheat on microstructure, topologically close-packed (TCP) phases, γ?′ precipitation and mechanical properties of an experimental Ni-base superalloy were studied. The investigated alloys were produced by investment casting process under two levels of superheat. After solution heat treatment, at 1180°C for 2?h followed by air cooling; the two alloys under investigation were isothermally exposed at 845°C for 24, 200, 1000, and 1500?h. The long-term thermal exposure conditions have a significant impact on the precipitation and morphology of TCP and γ?′ phases. The σ phase precipitated as needle and platelet shapes, whereas the μ phase formed in plate and agglomerated shapes. The μ phase has high concentration of Cr, Mo, W, and Co, while the σ phase has high percentages of Ni and Ti. The μ phase was precipitated after thermal exposure of 200?h in the case of high superheat specimen and after 1000?h in low superheat specimen. The η phase found was also a thick plate-like shape in the microstructure of both alloys in the interdendritic zones. The optimum size and volume fraction of γ?′ precipitates were obtained after being thermally exposed for 200 and 1000?h for high and low superheat alloys, respectively. Consequently, the highest hardness level was achieved at the optimum conditions of γ?′ precipitates in high and low superheat alloys.     

激光熔覆修复定向凝固镍基高温合金及其拉伸性能

高Al、Ti含量的定向凝固镍基高温合金在传统的修复过程中由于较大的热输入，存在严重的热裂倾向。利用激光热量集中、能量输入小的特点，可以有效控制修复过程中的热输入，从而减小铸造基体的晶界液化和开裂倾向。在优选参数下，可以获得无裂纹的修复组织，并可实现定向凝固组织的连续生长。对修复组织进行热处理，结果表明热处理过程不会促使裂纹产生，也不会影响熔覆层组织的定向凝固特征，但对于其内部γ′相的析出行为及形貌有较大影响，从而影响了沉积层的力学性能。对沉积层的拉伸性能测试表明，无论在常温还是高温(900 ℃)下，沉积层的拉伸性能都达到了铸造基体拉伸性能的80%以上，而且均为塑性断裂，一定程度上满足了实际修复需求。     

锰青铜表面激光熔覆镍基合金的微观组织

用Rofin-Sinar CW025 YAG激光设备,采用同步送粉的方式进行自熔性Ni-Cr-B-Si合金粉末的激光熔覆,获得了无气孔和裂纹缺陷的熔覆层.借助扫描电子显微镜(SEM,LEO 1450)、能谱仪(EDS),X射线衍射(XRD)对激光熔覆层进行组织、成分及物相分析.研究结果表明,激光熔覆层与C86300铜合金基体实现了良好的冶金结合,激光熔覆层组织主要是γNi,Cr7C3,Ni2B,Ni3B以及少量CrB2和Cr3Si,并且实现了主要元素(Cr,Fe,Ni,Cu和Zn)从基体到熔覆层的梯度分布.     

激光原位碳化铬-镍基复合涂层的组织特征

为了制备陶瓷增强镍基复合涂层,采用激光熔覆技术在45#钢表面原位合成了碳化铬-镍基复合涂层,研究了涂层的显微组织、相结构特征及显微硬度。碳化铬陶瓷的形状主要有四边形（菱形）、六边形和不规则块状;四边形碳化铬为Cr3C2,六边形碳化铬为Cr7C3,不规则块状碳化铬成分不确定,可能为Cr3C2或Cr7C3;涂层的平均显微硬度达到基体的3.5倍;涂层具有较高的硬度和致密的组织。结果表明,涂层主要由Cr-Ni-Fe-C,C,Cr7C3和Cr3C2四相组成,显微组织均匀致密,与基体呈良好的冶金结合。该研究对激光原位碳化铬-镍基复合涂层的理论研究和实际应用是有一定帮助的。