Structure of NiCrAlY coatings deposited on single-crystal alloy turbine blade material by laser cladding

In the present work single and multiple layer NiCrAlY coatings were produced by laser cladding on (100) single-crystalline substrates of SRR99 Ni-based superalloy. Detailed structural characterisation and texture analysis by optical microscopy, scanning electron microscopy, X-ray diffraction and Rutherford backscattering showed that the NiCrAlY coatings consisted essentially of γ phase with yttrium oxide (Y₂O₃) and a small proportion of yttrium–aluminum garnet (Al₅Y₃O₁₂) precipitated in the interdendritic regions. The coatings presented a columnar dendritic structure grown by epitaxial solidification on the substrate and inherited the single-crystalline nature and the orientation of the substrate. The coating material also showed a mosaicity and a defect density similar to those of the substrate. It can be expected that the protective effect of these coatings against oxidation is greatly enhanced compared with polycrystalline coatings because high diffusivity paths, such as grain boundaries, are eliminated in single-crystalline coatings, thus reducing mass transport through the coating.     

金属构件激光熔覆强化的研究

以45钢作为基体材料,对激光熔覆工艺参数中的激光熔覆功率、扫描速度对熔覆层质量的影响进行了探讨,并得出最佳的激光熔覆工艺参数。对试件进行了激光熔覆修复实验,修复后试件的表面硬度、耐磨性、耐腐蚀等性能得到明显提高。     

航空发动机制件报废锻压模具激光熔覆修复研究

采用自配的合金粉末,利用激光熔覆技术,对航空发动机制件报废高温锻压模具进行了修复.利用OM、SEM、XRD、显微硬度计对熔覆层的组织结构及硬度进行了研究.结果表明,熔覆层与基材实现了良好的冶金结合,熔覆层基体相为α-Fe,基体相上分布着结晶析出的Fe5C2、Fe2B、FeSi等相,还有一定量的非晶组织.熔覆层最表面硬度较低为670 HV0.2,在熔覆层内部硬度变化不大,平均为730 HV0.2.     

GH4133高温合金激光深熔焊温度场数值模拟

对航空材料GH4133高温合金激光深熔焊接过程进行了有限元数值模拟分析,建立了高斯旋转曲面体热源的热输入模型,得到了基于小孔模型的温度梯度曲线分布.结果表明,激光焊接小孔深度方向的热传导速率大于小孔径向的热传导速率;小孔前端的热梯度远大于小孔后端,小孔和熔池形状均为长椭圆形;距离焊缝不同位置处各点的升温过程相比焊缝中心具有延迟性,且温度峰值大大降低.     

GH150高压压气机叶片激光熔覆实验研究

本文通过选择合理的涂层合金配方及工艺参数,并在熔覆材料中加入3%wt左右的YO的稀土氧化物,可在GH150基体上获得无显微裂纹缺陷、显微组织均匀、熔覆层硬度与基体匹配良好、耐蚀性能显著提高的优质激光熔覆层。     

钛合金表面激光熔覆材料体系与熔覆层质量的研究现状

激光熔覆技术是代表表面工程发展方向和水平的表面改性新技术之一。钛合金具有诸多优良的性能,已在航空、航天、海洋、石油化工及生物医学工程等领域中广泛用作各种关键结构零部件,且随着工业技术的不断进步,其应用领域及应用量愈来愈广、适用条件变得愈来愈苛刻,对钛合金的性能要求也愈来愈高。在钛合金表面激光熔覆涂层可显著改善其耐磨和抗高温氧化等性能,在工业上具有广阔的应用前景。钛合金表面激光熔覆材料的选择与熔覆层质量的研究对于激光熔覆技术在钛合金表面的应用具有极为重要的意义。     

激光熔覆工艺对镍基碳化钛熔覆层组织的影响

通过对激光熔覆镍基碳化钛熔覆层组织的微观形貌和成分分析,研究了激光功率和扫描速度对熔覆层的碳化钛和硬质相碳化物的溶解和析出后的形态的影响。结果表明,使用较低功率或较高的扫描速度时,熔覆层中出现了未熔化的碳化钛,功率较大和扫描速度较低时,碳化钛全部以树枝晶的形态从液态镍中析出来。达到一定的功率时,硬质相碳化物是从液态镍中析出的二次相,且当扫描速度较快时,熔覆层还会出现成分不均。     

超塑成形对GH4169合金激光焊接组织的影响

采用激光连接/超塑成形组合技术制造了GH4169合金三层板结构件,研究了超塑成形(温度965℃,成形时间130min)对GH4169高温合金激光焊接组织的影响.试验结果表明:GH4169高温合金激光焊接组织主要由树枝晶构成,枝晶间中有Nb元素偏聚现象,即形成了一种金属间化合物Laves相;焊接组织在超塑成形后,焊缝中心出现了粗大的等轴晶粒,熔合线附近的柱状晶粒变得粗大,成形后大部分Laves相转变为δ相,但仍有少部分Laves相保留了下来;成形后焊缝的维氏硬度明显提高,由成形前的331.63HV0.1提高到391.74HV0.1,接近成形后母材的硬度415.63.超塑成形对GH4169高温合金激光焊接组织有明显的改善作用.     

Effect of laser cladding process parameters on clad quality and in-situ formed microstructure of Fe-TiC composite coatings

Over the past decade, researchers have demonstrated interest in tribology and prototyping by the laser cladding process. In-situ laser cladding enables the formation of a uniform clad by melting the powder to form desired composition from pure powder component.In this research pure Ti, graphite, and Fe with max particle sizes of 40 μm (0.04 mm) are used for in-situ laser cladding on a steel substrate. The effects of laser parameters on the quality of an in-situ formed TiC-Fe based composite clad are investigated. Laser parameters have an important role in clad quality and crack formation. They affect the bonding between clad/substrate and cooling rate. Diverse microstructures have been detected in the clad. Finally a model is developed in order to explain the formation and morphology of TiC. The melting and solidification stages of TiC formation and matrix confirm the suggested model.TiC particles increase the clad hardness to an average of four times greater than substrate's hardness. Experimental methods such as, XRD and SEM are used for phases characterization.     

激光熔覆修复的GH864合金烟气轮机动叶片失效原因分析

通过断口的宏观和微观分析及金相检验,对两起激光熔覆修复的GH864合金烟气轮机动叶片的断裂原因进行了分析.结果表明,两起事故都是由叶片激光熔覆层中缺陷引起的疲劳断裂,同时还分析了过渡区附近的沿晶裂纹产生原因,并提出了一些建议.     

磷含量对细晶镍基GH4133合金力学性能的影响

适当磷含量可提高细晶镍基GH4133合金的力学性能．采用控制热加工和热处理的方法将GH4133合金的晶粒度细化至ASTM 10级．该细晶合金的最低屈服强度比晶粒度为ASTM4—5级正常组织的合金高200MPa以上，最低断裂强度高150MPa以上．磷含量为0．140％(质量分数，下同)的细晶合金的屈服强度相对于正常磷含量(0．005％)的细晶合金又高约100MPa，断裂强度约高50MPa．镍基GH4133合金中，磷含量低于0．140％，拉伸试样均呈穿晶断裂．磷含量低于0．023％时，冲击断口呈穿晶断裂，冲击韧性高于70MJ／m^2；磷含量升至0．140％时，冲击断口部分区域呈沿晶断裂，冲击韧性约降至40MJ／m^2．延长GH4133合金持久寿命的最佳磷含量位于0．011％附近．结合位错与磷原子气团的相互作用讨论了上述不同载荷方式下磷对合金力学性能的影响特点．     

锆合金激光熔覆镍基复合层微观组织及界面特征

以Ni35自熔性合金粉末为熔覆材料,采用激光熔覆技术在锆合金表面原位生成了NiZr₂/陶瓷增强镍基涂层.利用金相显微镜、扫描电镜、X射线衍射仪等对熔覆界面附近的微观组织、物相组成及界面结合特征进行分析.结果表明,熔覆层基体组织为NiZr+Ni₁₀Zr₇,增强相NiZr₂以细针状均匀分布在熔覆层上部和底部,块状及棒状的陶瓷相Zr₅（Si_xNi_1-x）₄/Zr（Si_xNi_1-x）分布在熔覆层中部,熔覆层与基体间实现良好的熔焊冶金结合,界面结合区组织不均匀,分布有等轴状NiZr及晶间的α-Zr,熔覆层的显微硬度分布均匀,平均值约为1 100 Hv.     

GH4169合金叶片制坯成形工艺数值模拟优化

基于塑性有限元原理,应用Deform数值模拟平台,通过变形温度、压下量对挤杆成形及变形速度、摩擦条件对镦头成形的各场量进行深入研究,全面揭示了GH4169合金叶片制坯过程成形规律,并对其工艺参数进行优化.结果表明:适当的提升锻造温度有利于挤杆锻后温度的平稳分布;变形温度的增大使杆部各区域金属流动速度差异逐渐缩小,挤杆为...     

GH4133B合金组织特征及平衡相析出热力学研究

采用Thermo-Calc热力学计算软件,对GH4133B合金平衡析出相进行模拟计算分析,并进一步对该合金的显微组织特征进行观察分析。结果表明,Ti、Al含量对γ’相析出影响严重,并给出了定量计算结果。C含量能影响M23C6的析出量,对其析出温度没有影响;而Cr含量则主要影响其析出温度,对M23C6的析出量却没有影响。进一步对Ti、Al含量对η相的析出进行了计算分析,实验验证了时效过程中η相的析出及分布形态。     

激光熔覆45钢复合材料力学性能实验

对在45钢表面激光熔覆Ni60+20%WC复合粉末制备复合材料室温下的抗拉强度、冲击韧度和显微硬度进行研究。实验表明,45钢表面激光熔覆Ni60+20%WC复合粉末制备的复合材料,室温下的抗拉强度较基材略有下降,但冲击韧度较基材有明显的提升,提高幅度约28%;熔覆层硬度值远大于基体硬度值,从而提高其耐磨性。     

Q345钢激光熔覆的残余应力分析

针对因残余应力而出现的熔覆层表面开裂等问题,设计了合理的试验方案,获得熔覆与冷却过程中工件的残余应力值。根据残余应力值比较不同工艺路线的优劣,发现工件预弯能够显著降低残余应力。同时使用ANSYS进行仿真分析,模拟工件的温度场与应力场。分析得到,工件因纵向塑性畸变而产生的纵向应力是残余应力的主要成分。     

Technological and scientific landscape of laser cladding process in 2007

In the last 30 years, public and private organizations involvement in laser cladding R&D activities is increasing. These activities are mainly conducted in universities, public research institutes and technical centres of private companies worldwide. This study shows a bibliometric analysis of the patents and scientific publications in the laser cladding field for the period ranging from 1985 to 2007. This seeks to identify the activity and trends in its environment for strategic purposes. All the laser cladding processes and all the substrates (steel, aluminium and superalloys) used for coating, repairing and 3D fabrication were taken into account. At first, the world patent production was analysed in terms of volume (580 patent families found since 1985), frequency and applications. Then, the same strategy was applied to the scientific publications for a total volume of 588 targeted papers. Using bibliometric techniques, an analysis and mapping of the information was performed to highlight the temporal, geographical and institutional aspects of R&D activities. The patented applications were also classified in order to identify opportunities. This study shows the evolution of the scientific and technological environments of the laser cladding technology and can help public or private organizations to generate new ideas, gain awareness of emerging trends and validate the relevance of projects.     

Effect of clad ratio on interfacial microstructure and properties of cladding billets via direct-chill casting process

Numerical simulation and experiments were introduced to develop AA4045/AA3003 cladding billets with different clad-ratios. The temperature fields, microstructures and mechanical properties near interface were investigated in detail. The results show that cladding billets with different clad-ratios were fabricated successfully. Si and Mn elements diffused across the bonding interface and formed diffusion layer. With the increase of clad-layer thickness, the interfacial region transforms from semisolid–solid state to liquid–solid state and the diffusion layer increased from 10 to 25 μm. The hardness at interface is higher than that of AA3003 side but lower than that of the other side. The bonding strength increased with the clad-layer thickness, attributing to solution strengthening due to elements diffusion. The cladding billets were extruded into clad pipe by indirect extrusion process after homogenization. The clad pipe remained the interfacial characteristics of as-cast cladding billet and the heredity of clad-ratio during deformation was testified.     

Effects of the cladding parameters on the deposition efficiency in pulsed Nd:YAG laser cladding

The purpose of the present study is to analyze the effects of the cladding parameters on the deposition efficiency in cladding of Co alloy powder by a low power pulsed Nd:YAG laser, and to optimize the cladding parameters for maximizing the deposition efficiency. Experiments were designed, conducted and analyzed by the Taguchi experimental method using a L18 orthogonal array. It was found that the powder feed position, powder feed angle, powder feed rate and travel speed had significant effects on the deposition efficiency, but the shielding gas type, laser pulse shape and focal position had nearly no effects. The optimal cladding conditions in the experimental range were obtained at 0 mm of the powder feed position, 50° of the powder feed angle, 0.62 g/s of the powder feed rate and 6.7 mm/s of the travel speed. From the confirmation experiment, the average deposition efficiency of 12.3% was achieved at the optimized cladding conditions as statistically predicted.     

双向扫描激光熔覆止裂机理及试验分析

针对激光熔覆过程中易出现的熔覆层开裂的问题,采用了单向送粉双向扫描激光熔覆工艺,较好地抑制了熔覆层的开裂.通过对激光熔覆过程温度场、应力场进行计算分析,发现采取单向送粉单向扫描工艺时,熔覆层顶部以及与基体接合处会出现明显的应力集中现象,且应力水平较大,而采取双向扫描工艺后,熔覆层内拉应力水平显著降低,且熔覆层顶部的应力...