镍基金刚石复合涂层的冷喷涂制备

通过机械合金化法制备了金刚石/NiCrAl复合粉末,探讨了金刚石含量对粉末的组织结构、粒度分布的影响.采用冷喷涂沉积法制备金刚石增强金属陶瓷涂层,探讨了粉末结构、金刚石含量对涂层的成分及组织结构的影响.实验结果表明,在机械合金化过程中,金刚石和NiCrAl并没有发生反应生成新相,硬质相较均匀地分布在复合粉末中.分析冷喷涂制备的复合涂层的组织结构发现,喷涂过程中粉末的成分及组织结构完全保留到了涂层中.     

铝粉包覆镍铬合金粉末及涂层性能研究

采用常规铝粉及超细铝粉对镍铬合金粉进行包覆,制备镍铬铝粉末.结果表明,采用超细铝粉包覆的粉末表面包覆更严、更均匀.采用超细铝粉对两种形状不同的镍铬合金粉进行包覆,形状不规则的粉末更易被包覆.将以上三种包覆型粉末制备成涂层,超细铝粉包覆粉末制备的涂层孔隙率更小,涂层更致密.     

Producing NiCrAl alloy by the SHS method for use in thermal spray powder manufacturing

A series of Ni alloys containing 36.15–44.54 wt.% Cr and 2.0–13.50 wt.% Al was synthesized by Self-Propagating High-Temperature Synthesis (SHS) using a mixture of NiO, Cr₂O₃ and Al powders in order to obtain low-cost starting materials for thermal spray powder production. The experiments were carried out with the addition of an excess stoichiometric amount of Al between 0 % and 30 %. Additions of CaO and CaF₂ were also done to remove sulfur from the alloy and to investigate the effect on metal recovery. Thermochemical simulations of the SHS processes were examined with the FactSage program. The products were characterized by chemical analysis, X-ray diffraction (XRD), electron probe microanalysis (EPMA) and microhardness techniques.     

Correlation of microstructure and high temperature oxidation resistance of plasma sprayed NiCrAl, NiCrAlY, and TiAlO composite coatings on Ti−6Al−4V

In the present study Ni−18Cr−6Al, Ni−22Cr−10Al−1Y and TiAlO composite powders were coated on Ti−6Al−4V substrates by atmospheric plasma spraying, and the coated specimens were evaluated by isothermal and cyclic oxidation resistance tests at 800°C. The oxidation kinetics of the plasma sprayed NiCrAl, NiCrAlY, and TiAlO composite coated specimens obey a parabolic rate law. The oxidation resistance of the plasma sprayed NiCrAl and NiCrAlY coatings is superior to that of plasma sprayed TiAlO composite coating. The best oxidation resistance was observed in the plasma sprayed NiCrAlY coatings. This is mainly attributed to the formation of Y−Al−O complex oxides and Ni₃Al with higher thermal stability on the coatings.     

Effects of Cr and Al Contents on the Preparation of SiC Fiber-Reinforced NiCrAl Alloy Matrix Composite

In this work, the effects of Cr and Al contents on the preparation of SiC fiber-reinforced NiCrAl alloy matrix composites (SiC_f/Ni-20Cr-5Al, SiC_f/Ni-15Cr-5Al, SiC_f/Ni-10Cr-5Al and SiC_f/Ni-10Cr-3Al) were thoroughly discussed. The composites were prepared by vacuum hot pressing process using matrix-coated fibers. It was found that Cr solute atoms played a significant role in retarding the recrystallization of NiCrAl alloy matrix, and the Al elements in the form of γ′-Ni₃Al phase had a suppression effect on the plastic flow of the matrix. Therefore, the reduction in Cr and Al contents was conductive to the recrystallization and plastic flow of NiCrAl alloy matrix, thereby reduced the size and number of micro-voids in the composite. In addition, this work provides some guidance for designing and manufacturing reasonable SiC fiber-reinforced Ni alloy matrix composites.     

18O Tracer studies of Al2O3 scale formation on NiCrAl alloys

Diffusion processes in Al ₂ O ₃ scales formed on NiCrAl + Zr alloys were studied by the proton activation technique employing the ¹⁸ O isotope as a tracer. The ¹⁸ O profiles identified a zone of oxide penetration beneath the external scale. Both this subscale formation and the outer Al ₂ O ₃ scale thickness were shown by this technique to increase with Zr content in the alloy. Estimated k _p 's from scale thicknesses were in agreement with gravimetric measurements for various Zr levels. Alternate exposures in O and ¹⁸ O revealed that oxygen inward transport was the primary growth mechanism. A qualitative analysis of these ¹⁸ O profiles indicated that the oxygen transport was primarily via short-circuit paths, such as grain boundaries.     

等离子喷涂WC-12Co/NiCrAl复合涂层的摩擦磨损特性

以NiCrAl涂层为粘结层,用等离子喷涂工艺在TC4钛合金表面制备了WC-12Co/NiCrAl复合涂层。通过扫描电镜(SEM)、能谱仪(EDS)、X射线衍射仪(XRD)和显微硬度仪等手段分析了涂层微观形貌、化学成分和显微硬度,并用磨损试验考察了WC-12Co/NiCrAl复合涂层的摩擦磨损特性。结果表明:WC-12Co涂层表面未熔颗粒较多,涂层截面孔隙率为10.2%;WC发生部分分解,出现W2C、Co6W6C等新相;涂层与基体结合界面为机械结合+局部微冶金结合方式;显微硬度为双态Weibull分布,呈现不同位置结构的差异化。WC-12Co涂层表现出良好的减摩及耐磨性能,同载荷下摩擦因数低于基体,磨损失重为基体的1/10,磨粒磨损是其主要磨损机制。     

Y，La改性Ni-10Cr-5Al合金的循环氧化行为研究

通过添加0.1%(质量分数)的单一稀土La和复合稀土Y-La,研究了两种含稀土的Ni-10Cr-5Al(质量分数,%)合金在1 100℃和1 200℃下的高温循环氧化行为。采用热重法并结合X射线衍射、扫描电子显微镜、能谱仪等,研究了合金的循环氧化动力学、氧化物的物相和组织成分等演变规律,分析了含稀土Ni-10Cr-5Al合金的氧化膜粘附性能在不同氧化温度下的差异及机制。结果表明,在1 100℃时,Ni-10Cr-5Al合金中添加0.1%(质量分数)的La或Y-La,不仅减少了氧化膜的厚度,而且因形成"钉扎"作用提高了氧化膜的粘附性,从而改善了合金的抗循环氧化性能。且复合添加Y-La的效果优于单一添加La的效果。但在1 200℃时,合金沿晶界的内氧化加快,反而恶化了合金的抗循环氧化性能。     

Temperature effect on the role of yttrium in oxidation behaviour of NiCrAl alloys

Temperature effect on the oxidation behaviour of NiCrAl and NiCrAl-Y alloys has been studied in the present work. Thermogravimetric analysis has been carried out at 900, 1000, 1100 °C for 210 h in order to investigate oxidation kinetics. Phase constitution of surface scales was determined by using X-ray diffraction, and microstructure was examined by using scanning electron microscope with energy dispersive spectra. Oxidation resistance of NiCrAl alloy has been found to be improved substantially by adding rare earth element yttrium at all the three experimental temperatures. But Y-rich inclusions result in higher initial oxidation rates as a result of oxidation of the inclusions.     

基于正交试验的等离子喷涂 NiAl 和 NiCrAl 涂层工艺研究

基于正交试验研究了等离子喷涂 NiAl 和 NiCrAl 涂层过程中结合强度与等离子喷涂参数之间的响应关系, 分析了涂层显微特征的影响因素并据此优化了工艺参数。结果表明,影响 NiAl 涂层结合强度的因素主次顺序为 氢气流量、氩气流量、电流、喷涂距离,影响 NiCrAl 涂层结合强度的因素主次顺序为喷涂距离、氩气流量、电 流、氢气流量,工艺优化能够显著改善 NiAl 和 NiCrAl 涂层的显微特征和性能。NiAl 涂层的工艺范围为氩气流 量 110~120 SCFH,氢气流量 20~25 SCFH,电流 600~610 A,喷涂距离 130~140 mm,结合强度均在 30 MPa 以上, 最大值为 33 MPa。NiCrAl 涂层的工艺范围为氩气流量 120~130 SCFH,氢气流量 25~30 SCFH,电流 610~620 A, 喷涂距离 130~140 mm,最大结合强度为 43.6 MPa。