电沉积纳米镍合金及其复合材料的超塑性

采用脉冲电沉积技术制备纳米镍合金及Ni/Si3N4(w)复合材料,在应变速率为1×10-3～2×10-2 s-1,温度为673～823 K的条件下,研究它们的超塑性拉伸变形行为,确定最佳超塑性条件并获得最大伸长率.结果表明,Ni-Co合金在773 K,应变速率5×10-3 s-1时,最大伸长率为279%;Ni/Si3N4(w)复合材料在713 K,应变速率1×10-2 s-1时,最大伸长率为635%.采用SEM 和TEM对电沉积和超塑变形前后试件的显微结构进行表征.应用晶粒长大行为和协调机制对合金和复合材料的超塑性进行对比研究和讨论.     

The Influence of Ultrasonic Frequency on the Properties of Ni-Co Coatings Prepared by Ultrasound-assisted Electrodeposition

In this paper, Ni-Co coatings were electrodeposited onto carbon steel substrates with the aid of ultrasonic agitation. The coatings were analyzed by energy dispersive X-ray analysis （EDX）, X-ray diffraction analysis （XRD） and scanning electron microscopy （SEM）. The effects of the ultrasonic frequency on the roughness, hardness and corrosion resistance of the Ni-Co coatings were also investigated. The results indicated that the increase of the ultrasonic frequency from 20 to 120 kHz reduced the Ni content and the grain size of Ni-Co coatings. Moreover, the phase structure of the electrodeposited coatings was influenced by the ultrasonic frequency. Under 55 kHz ultrasonic agitation, the Ni-Co coating was single fcc phase and showed the finest roughness and the strongest corrosion resistance in 5 wt.% NaCl solution at the ambient temperature. Under ultrasonic agitation with frequency of 90 kHz, the coating was a mixture of fcc and hcp structure and showed the maximal hardness of about 420 HV. Therefore, ultrasonic agitation helped decrease the roughness, and enhance hardness and corrosion resistance of Ni-Co coatings.     

占空比对高频脉冲电沉积( Ni-Co) / 纳米 Al2O3复合镀层的影响

采用高频脉冲电沉积法制备(Ni-Co)/纳米Al2O3复合镀层,研究了占空比对复合镀层沉积速率、成分、形貌及表面显微硬度的影响。结果表明:随着占空比由0.3提高至0.5,复合镀层的沉积速率增加,晶粒尺寸变大,表面变粗糙,并且Co含量降低,Ni含量增加,纳米Al2O3颗粒含量变化不明显,Co含量的降低导致硬度降低。     

高频脉冲电镀镍钴合金工艺及性能的研究

采用高频脉冲电流，制备Ni-Co复合镀层。通过正交试验设计的方法，重点考察了脉冲频率、占空比、平均电流密度、镀液pH值、温度及CoSO4·7H2O的浓度对镀层在15％H2SO4溶液中的阳极极化行为的影响，从而遴选出最佳电镀工艺：脉冲频率140kHz，占空比0．25，平均电流密度3A／dm，镀液pH值3，温度45℃，硫酸钴浓度20g／L。同时，对高频脉冲电镀与直流电镀进行比较。     

爆炸喷涂Ni-Co/WC涂层的微观组织与性能

介绍了Ni-Co/WC涂层爆炸喷涂工艺,并研究了爆炸喷涂Ni-Co/WC涂层性能.研究表明,该涂层除了有良好的力学性能, 还具有很好的耐磨性和耐腐蚀性.涂层微观组织分析表明,涂层组织中的微晶和非晶相对涂层的耐磨性和耐腐蚀性都有重要的意义.     

Measurement and analyses of molten Ni-Co alloy density

1Introduction Ni-based heat-resistant alloys are widely applied in aerospace industry to make critical components such as the blades in gas-turbine engines.Their density in liquid state is very important to investigate the structure of liquid alloy,model …     

Improvement of the oxidation resistance of superalloys by low-pressure,plasma-sprayed MCrAlYTa coatings. I

The oxidation behavior of two superalloys (CMSX2 and IN100) protected by low-plasma-pressure-sprayed MCrAlYTa coatings (M = Co, Ni) was studied with emphasis on the kinetics and microstructural aspects. The oxidation behavior of each alloy (substrate and coating) was studied separately in order to obtain a better understanding of the oxidation mechanism of duplex systems (coated substrate) under both isothermal and cyclic conditions (mainly at 1100°C and in 1 atm O₂). Although all these systems develop an alumina scale, differences were observed as a result of several factors: (1) the coating and substrate composition, thus the presence, amount and distribution of addition elements (Y, Ta, Ti, C,...); (2) the interdiffusion phenomena that induce microstructural modifications; and (3) the porosity amount and roughness of the coating. The system that appears to be the most resistant against cyclic oxidation consists of CoNiCrAlYTa-coated IN100. This cannot be explained by the present study. Further work was conducted, particularly on the oxidation stresses, as described and discussed in paper II.     

四硼酸钠对Ni-Co合金镀层的影响

为提高Ni-Co合金镀层硬度,采用单因素实验研究四硼酸钠对Ni-Co合金镀层硬度的影响,利用硬度测试考察Ni-Co合金镀层硬度的变化,采用金相显微镜对镀层微观形貌进行分析,通过X-射线衍射及能谱分析镀层的相组成和成分,采用电化学测试考察复合镀层耐蚀性。结果表明,当溶液中加入四硼酸钠时,Ni-Co合金镀层中的镍、钴发生变化,镍增加,钴减低,当四硼酸钠为15 g/L时镀层晶粒更加细致,外观表面更加光亮,镀层表面形貌达到最佳;腐蚀电流为9.422μA,硬度达到467.4 HV。     

Microstructure and characterization of Ni-Co/Al2O3 composite coatings by pulse reversal electrodeposit

Ni-Co/Al₂O₃ composite coatings were obtained by pulse reversal electrodeposit (PRC) and direct current electrodeposit (DC). The microstructure of the coatings was characterized by means of SEM, XRD and TEM. Hardness, wear resistance and macro residual stress of coatings were also investigated. The results showed that the microstructure and performance of the coatings were significantly affected by the electrodeposit methods and the Al₂O₃ particles content. The PRC composite coatings exhibited compact surface, high hardness and excellent wear resistance. The macro residual stress of PRC composite coatings was lower than that of DC ones. With the increasing of Al₂O₃ particles content, the hardness and wear resistance of the composite coatings increased.     

高频脉冲电镀镍-钴合金沉积速率的研究

采用高频脉冲电流,制备Ni-Co合金镀层。通过正交试验设计的方法,重点考察了脉冲频率、占空比、平均电流密度、温度及CoSO4的浓度对镀层的沉积速率及镀层在15%H2SO4溶液中耐蚀性的影响,从而遴选出最佳电镀工艺:脉冲频率120 kHz,占空比0.2,平均电流密度10 A/dm2,温度60℃,硫酸钴质量浓度40 g/L。并分析了最佳工艺得到的镀层表面形貌。