热处理对n-ZrO2/Ni复合刷镀层接触疲劳性能的影响

采用电刷镀技术制备了n-ZrO2/Ni纳米复合镀层,研究了镀层的接触疲劳性能.结果表明,含有纳米颗粒的复合镀层表面比较细腻,但由于镀层脆性较大,其接触疲劳性能较纯镍镀层差;复合镀层经热处理退火(400℃×30min)后,其接触疲劳性能有较大提高.镀层疲劳断口的SEM分析表明,n-ZrO2/Ni纳米复合镀层脆断特征明显,退火处理能使其脆性得到改善.     

n-Al2O3/Ni复合镀层的组织与接触疲劳行为

利用SEM和TEM分析了n-Al2O3／Ni复合镀层的表面形貌和微观组织,研究了该镀层的接触疲劳行为。结果表明,复合刷镀层的表面形貌细腻,镀液中纳米Al2O3颗粒含量较低时这些颗粒在镀层中呈弥散分布,而含量较高时存在一定的团聚。随着镀液中纳米Al2O3颗粒含量的增加,复合镀层的接触疲劳寿命逐渐增加,含量为20g/L时达到最大,约为190万次,是纯镍镀层的1．5倍;含量进一步增加时,寿命急剧降低。失效分析表明,纯镍镀层的疲劳断口发生强烈的塑性变形;镀液中纳米Al2O3颗粒含量为40g/L时,复合镀层的疲劳断口呈现脆性断裂特征。     

脉冲换向电刷镀镍基纳米SiO2复合镀层的耐腐蚀性能研究

采用脉冲换向电刷镀方法制备了Ni/n-SiO2复合镀层,应用SEM对镀层表面形貌进行了分析,测试了镀层的孔隙率,以及镀层在海水浸泡条件下的耐腐蚀性能,讨论了镀层的耐腐蚀机理.实验结果表明:与直流工艺条件下的电刷镀镀层相比,脉冲换向电刷镀工艺得到的Ni/n-SiO2复合镀层具有致密精细的表面、较小的孔隙率和较高的耐腐蚀性能.     

纳米Al2O3／Ni复合电刷镀层的表征与微动磨损机理

通过在镍基电刷镀液中添加纳米Al2O3颗粒,制备出了分散均匀、与基质金属Ni结合良好的Al2O3／Ni复合电刷镀层。复合镀层的组织致密,显微硬度高。微动磨损试验表明,复合镀层在常温及高温下抵抗微动磨损的能力均强于普通快镍镀层。这是因为,随着纳米颗粒的加入,Al2O3／Ni复合电刷镀层受到细晶强化、位错强化和弥散强化,抵抗塑性变形和粘着破坏的能力增强,从而具有良好的耐微动磨损性能。     

电刷镀Ni／n-SiO2复合镀层的形貌及摩擦学性能研究

利用脉冲换向电刷镀方法制得了Ni／n—SiO2复合镀层，并对镀层进行了表面形貌观察和分析，测试了镀层的摩擦学性能，与直流工艺条件下的快镍镀层和Ni／n—SiO2复合镀层相比，采用脉冲换向电刷镀工艺得到的Ni／n—SiO2复合镀层，由于脉冲换向电流的细晶强化作用和纳米颗粒的弥散强化作用，镀层致密、晶粒团尺寸细小、硬度高、摩擦系数低，因此耐磨性能更好。     

电流特性和纳米颗粒对电刷镀复合镀层耐腐蚀性能的影响

为获得性能优良的镀层,利用不同的电沉积方法(直流、脉冲电流及脉冲换向电流)制得了Ni、Ni/n-SiO2和Ni/n-Al2O3复合镀层,分别对其表面形貌(SEM)进行了观测和分析,测试了镀层的孔隙率,并通过海水浸泡方法检测其耐腐蚀性能.比较测试结果后发现:电流特性和纳米颗粒对电刷镀复合镀层的耐腐蚀性能均有影响,采用脉冲换向电流沉积得到的Ni/n-SiO2复合镀层具有致密精细的表面形貌、较小的孔隙率和较好的耐腐蚀性能.     

n-Al2O3/Ni复合电刷镀层滑动磨损性能

为了提高材料在含磨粒油润滑条件下的摩擦磨损性能，制备了n-Al2O3／Ni电刷镀复合镀层，采用扫描电镜观察了镀层的表面和截面组织以及纳米颗粒在复合镀层中的分布，以GCr15钢为对摩件对比了复合镀层与快速镍刷镀层以及45钢的摩擦磨损性能，并且对磨损试样表面的形貌和成分进行了分析。结果发现，纳米颗粒的加入细化了镀层组织，改善了镀层与基体的结合，提高了镀层的硬度；材料在含细沙油润滑条件下的磨损量与时间呈线性关系，复合镀层的摩擦系数和磨损量小于快速镍镀层和45钢。     

Ni-P-金刚石化学复合镀层的组织结构及性能

研究了Ni-P-金刚石复合镀层的组织结构及性能特点，结果表明：复合镀层镀态时为非晶结构；镀层经300℃，1h的热处理后开始晶化，晶化后形成品相Ni和Ni3P；与Ni—P镀层相比，Ni-P-金刚石复合镀层具有更好的硬度和耐磨性，特别是在镀态时差别更明显；但复合镀层的耐蚀性和抗氧化能力低于普通Ni-P镀层。     

电刷镀纳米复合镀层的接触疲劳性能研究

利用电刷镀技术制得了镍包覆n-Al2O3粒子的复合镀层.研究了镀层硬度与镀液中粒子含量的关系,并测试了纳米复合镀层的接触疲劳性能.结果表明,镀层的硬度随镀液中粒子含量的增加而增加,到30 g/L时达到最大,随后降低;镀层的接触疲劳寿命较高,能达到1 000 000次.     

纳米Al2O3p/Ni复合刷镀层的组织与性能研究

制备了纳米A2O3p／Ni的复合刷镀层，测试了复合刷镀层的硬度、耐磨性、抗接触疲劳性能及高温性能，并分析了复合刷镀层的金相组织。结果表明：纳米颗粒复合刷镀层的硬度是不含纳米颗粒的快速镍刷镀层的1．7倍，耐磨性是其2．5倍，抗疲劳寿命提高到10^6周次，可服役温度提高到450C；纳米颗粒复合刷镀层的强化机制主要为细晶强化，弥散强化和位错强化。     

Contact fatigue behavior of nano-ZrO2/Ni coating prepared by electro-brush plating

Nano-ZrO₂/Ni composite coatings were prepared through co-depositing nano-ZrO₂ particles and pure nickel by electro-brush plating (EBP). By analyzing the effects of microstructure, annealing and load on contact fatigue life, the contact fatigue behavior of the nano-ZrO₂/Ni EBP coating was investigated. Furthermore, the contact fatigue behaviors of the nano-ZrO₂/Ni EBP coating and the nickel EBP coating were compared. The results show that the nano-ZrO₂ particles in the as-deposited nano-ZrO₂/Ni EBP coating were partially conglomerated, and the microstructure of the annealed nano-ZrO₂/Ni EBP coating was finer. Under the as-deposited condition, the contact fatigue life of the nano-ZrO₂/Ni EBP coating was much lower than that of the nickel EBP coating. After the annealing process, the contact fatigue life of the nano-ZrO₂/Ni EBP coating was greatly increased and much higher than that of the nickel EBP coating. The scanning electron microscope (SEM) images of the fatigue fracture zones and the transmission electron microscope (TEM) images of microstructure of the deformation layer show that the annealing could improve the ductility of the nano-ZrO₂/Ni EBP coating, and the nano-ZrO₂ particles could restrain the propagation of the fatigue cracks, which contributed to the enhancement of the contact fatigue properties of the nano-ZrO₂/Ni EBP coating.     

Microstructural Characteristics and Oxidation Behavior of Low-Pressure Cold-Sprayed CoNiCrAlY Coatings

CoNiCrAlY coatings were deposited by low-pressure cold spraying and subsequently heat-treated at 1050 °C for 4 h in a vacuum environment. The microstructural characteristics and oxidation behavior of CoNiCrAlY coatings were investigated. The as-sprayed coating exhibited low porosity and oxygen content. The high plastic deformation of the sprayed particles led to significant refinement of γ-matrix and dissolution of β-(Ni,Co)Al phase in the as-sprayed coating. After heat treatment, the single phase (γ) in the as-sprayed coating was converted into a γ/β microstructure, and a continuous single α-Al₂O₃ scale was formed on the coating surface. Vacuum heat treatment can postpone the formation of spinel oxides within 100 h. After being oxidized at 1050 °C for 400 h, the heat-treated coating exhibited better oxidation resistance than the as-sprayed coating. The reduced growth rate of the oxide scale and the suppression of the formation of spinel oxides can be attributed to the vacuum heat treatment, as well as the intrinsic microstructure of the cold-sprayed coating. Finally, the effects of the microstructural changes induced during the cold spraying process on the growth of the thermally grown oxide and the oxidation mechanisms of the CoNiCrAlY coatings were discussed.     

Influence of heat treatment on microstructures and micro-hardness of n-SiO2/Ni composite coating

The n-SiO2/Ni composite electro-brush plating coating was prepared on the 1045 steel substrate. SEM and TEM were utilized to analyze the surface and cross-section morphologies or the microstructures of the composite coating before and after heat treatment, as well as a micro-hardness tester was used to measure the micro-hardness before and after heat treatment. The results show that the entrance of nano SiO2 particles into composite coating makes the micro-hardness higher. After heat treatment, due to the obstruction to growth of Ni crystals from nano particles, the composite coating still possesses a higher micro-hardness than that of common Ni-base coating.     

Properties and strengthening mechanism of brush plated nanoparticle reinforced composite coatings

Nanoparticle reinforced nickel matrix composite coatings, such as n-Al2O3/Ni, n-SiO2/Ni, n-SiC/Ni and n-TiO2/Ni, were fabricated by brush plating technique. Hardness, wear resistance and contact-fatigue resistance of the composite coatings were determined, and strengthening mechanism of the composite coatings was discussed. Results show that the composite coatings have superior properties to the Ni metal coating. Compared with properties of brush plated Ni metal coating, the composite coatings have hardness over 1.5 times and wear resistance capability of about 2.5 times. The strengthening mechanism of the composite coatings mainly includes fine-crystal grain effect, nanoparticle dispersion effect and dislocation effect.     

电接触强化对Ni/Cu复合镀层组织与性能的影响

利用电刷镀在铸铁表面制备了厚度在1 mm左右的Ni/Cu复合镀层,并对镀层进行了电接触强化试验。利用场发射电镜(FESEM)、维氏硬度计分析了电接触强化对镀层组织性能的影响。试验结果表明,电接触强化改善了镀层表面和内部质量,减少了镀层内部裂纹、孔洞等缺陷。同时,电接触强化使镀层和基体之间产生了部分镶嵌熔融。电接触强化改变了Ni层与Cu层的组织结构,使镀层组织更加致密紧实,Cu层和Ni层之间发生了塑性变形,产生了一定的镶嵌。强化后镀层表面及截面硬度都有所提升。镀层与基体之间形成的硬化层硬度远大于基体硬度,电接触强化提高了镀层与基体之间的结合力。     

大变形Ag/Ni20纤维复合电接触材料电弧侵蚀及形貌特征

采用包覆挤压、集束挤压、大变形冷拉拔等大变形技术制备出Ag/Ni20纤维复合电接触材料,研究该材料在直流条件下触点的电弧侵蚀,利用扫描电镜(SEM)、能谱(EDS)等方法分析电弧侵蚀后触点表面微观结构和元素分布,归纳出大变形Ag/Ni20纤维复合电接触材料具有浆糊状凝固物、珊瑚状结构、骨架结构、孔洞或气孔、裂纹等5种电弧侵蚀形貌特征。     

反应等离子喷涂Ni3Al涂层的组织与性能

为了满足高温热防护的需求,采用等离子喷涂技术制备Ni3Al复合涂层,并详细研究了涂层的组织结构、结合强度、热震性能及高温抗氧化性能。结果表明,由于Ni、Al粉体之间接触充分,喷涂过程中,完全反应生成了Ni3Al中间相,并放出大量的热,涂层与基体呈微冶金结合,结合强度较普通镍包铝涂层高30%~40%,并具有良好的抗热震性和高温抗氧化性能     

Microstructure evolution and hardening mechanisms of Ni-P electrodeposits

Ni-P alloy coatings with different phosphorus contents were prepared by electroplating in a nickel sulfate bath containing phosphorous acid (H₃PO₃). Hardening mechanism, such as dispersion hardening of Ni nano crystals in amorphous matrix of the as-deposited Ni-P coating and coarsening weakening of Ni₃P for the high P coating after 1 h of heat treatment at 400 °C were concluded from the experimental data. Hardening mechanism of Ni-P alloys were further discussed based on the microstructure evolution with increasing deposit P content and during the heat treatment by using high resolution TEM (HR-TEM). A maximum hardness was observed for the as-deposited and heat-treated Ni-P alloys with 4 wt.% and 6 wt.% P, respectively. These composition ranges corresponding to the microstructure with high hardness proposed are believed to be useful for the industrial applications and further study.     

金基电刷材料再结晶过程组织性能变化的研究

金银镍铜合金是一种优良的电刷材料,采用真空感应熔炼方法制备金银镍铜铸锭,通过轧制并配以中间热处理,使铸锭发生塑性变形,通过硬度检测、电阻率检测、扫描电镜对微观组织进行观察,研究金银镍铜合金在不同热处理条件、不同变形量下的力学性能变化。结果表明,金银镍铜合金塑性变形过程加工硬化现象明显,可通过加大变形量提高强度及电阻率。