MICROSTRUCTURE OF ELECTRODEPOSITED Ni-W-P-SiC COMPOSITE COATINGS

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Corrosion resistance of electrodeposited RE-Ni-W-P-SiC composite coating

Immersion experiment results show that corrosion rate of the as deposited RE Ni W P SiC composite coating in HCl solutions increases with the rise of HCl concentration. On the contrary, the corrosion rate of the composite coating after heat treatment decreases with increasing HCl concentration. The corrosion rates of the composite coatings in as deposited state and after heat treatment in H 2SO 4 and H 3PO 4 solutions respectively decrease with the rise of H 2SO 4 and H 3PO 4 concentrations. The corrosion rate of the composite coating as deposited in FeCl 3 solutions decreases with increasing FeCl 3 concentration, while the rate of the composite coating after heat treatment increases with the rise of FeCl 3 concentration. The corrosion rate of 316L stainless steel in the corrosion media of H 2SO 4, HCl, H 3PO 4 and FeCl 3 solutions at different concentrations increases with rising concentration. In addition, the corrosion rate of 316L stainless steel in the corrosion media of H 2SO 4, HCl, H 3PO 4 and FeCl 3 solutions respectively is much greater than that of the RE Ni W P SiC composite coating as deposited and after heat treatment in the same corrosion media. [

Microstructure of electrodeposited RE-Ni-W-P-SiC composite coating

The components and microstructure of the RE Ni W P SiC composite coating were analyzed by means of EPXDS, SEM and XRD. The results showed that the composite coating containing 5%～14%RE, 4%～7%SiC, 12%～15%P and 5%～6%W was obtained by use of appropriate bath composition and plating conditions. The as deposited composite coating is amorphous and it becomes mixture when the temperature is raised from 200 ℃ to 400 ℃. However, the composite coating is crystal when the temperature is over 400 ℃. Scanning electron microscopy indicates that the heat treatment temperature has no effect on the surface morphologies of the RE Ni W P SiC composite coating. This is to say that the composite coating has a better heat stability of microstructure and high temperature oxidation.

STUDY ON PROPERTIES OF PULSE ELECTRODEPOSITED RE-Ni-W-P-SiC COMPOSITE COATINGS

The effects of pulse frequency f and duty cycle r on the deposition rate, composition, morphology, and hardness of pulse electrodeposited RE （rare earth）-Ni-W-P-SiC composite coatings have been studied. The results indicate that pulse current can improve the deposition rate of RE-Ni-W-P-SiC composite coatings; W, P, and SiC contents in the coating decrease with the increase of pulse frequency and reach the lowest value at f = 33Hz, whereas the RE content in the composite coatings increases with the increase of pulse frequency. SiC content decreases with the increase of duty cycle, W content reaches the lowest value, and P content reaches the highest value at r = 0.4; pulse current and RE can lead to smaller size of the crystalline grains; however, the effects of different pulse frequency and duty cycle on the morphologies of RE-Ni-W-P-SiC composite coatings are not obvious. The hardness of RE-Ni-W-P-SiC composite coatings is the highest when the duty cycle is at 0.6 and 0.8 and pulse frequency is at 50Hz. At the same pulse frequency, the hardness of RE-Ni-W-P-SiC composite coatings at r= 0.8 is higher than that at r= 0.6.

PROPERTIES OF ELECTRODEPOSITED AMORPHOUS Ni-W-P-SiC COMPOSITE COATINGS

The Effects of heat treatment temperature on the hardness,wear resistance and structure of the amorphous Ni-W-P-SiC composite coatings have been investigated.The results show that Ni-W-P-SiC composite coatings are amorphous under 300℃, partially crystalline at 300-400℃,and crystalline when heat treatment temperature reaches 400℃,the crystals being fine Ni3P phase particles.The hardness,wear resistance and the crystallization temperature of the composite coatings increase when an additive is added into the bath.The hardness and wear resistance of the coatings increase with increasing heat treatment temperature,and they will reach their peak values when the heat treatment temperature reaches 400℃.Corrosion experiment indicates that the corrosion resistance of amorphous Ni-W-P-SiC composite coatings in various kinds of corrosive media except nitric acid is better than that of stainless steel 1Cr18Ni9Ti.Scanning electron microscopy observation shows that the additive has no effect on the surface appearance of the coatings,but the current density and the pH value have considerable effects on the surface appearance.

CATHODIC PROCESS AND WEAR RESISTANCE OF ELECTRO-DEPOSITED RE-Ni-W-P-SiC COMPOSITE COATING

Cathodic deposition current density of the composite coatings increases when SiC par-ticles and rare earth (RE) were added in the bath, which is profitable for Ni- W-P alloy to deposit in the cathod, forming Ni-W-P-SiC and RE-Ni-W-P-SiC composite coatings. On the contrary, the addition of PTFE in the bath decreases cathodic deposition current density of the coatings. The current density increases a little when the amount of RE is 7-9g/l; however, the current density increases greatly when the amount of RE is increased to 11-13g/l. Bui ij the amount of RE is raised further, the current density decreases. Hardness and wear resistance of RE-Ni-W-P-SiC composite coating have been studied, and the results show that the hardness and wear resistance of RE-Ni-W-P-SiC composite coating increase with increasing heat treatment tempera-ture, which reach peak values at 400℃; while the hardness and wear resistance of the coating decrease with the rise of heat treated temperature continuously.

RE-Ni-W-P-SiC-PTFE复合镀层的抗氧化性研究

研究了RE Ni W P SiC PTFE复合镀层的抗氧化性。结果表明 :RE Ni W P SiC PTFE复合镀层随着氧化温度的升高 ,氧化膜的重量增加 ,但在 80 0°C以下氧化温度对镀层的增重不显著 ;80 0°C以上 ,镀层的增重迅速增加。通过对三种镀层抗氧化性能的比较可知 ,RE Ni W P SiC PTFE镀层的抗氧化性不如Ni W P、Ni W P SiC及RE Ni W P SiC三种镀层好。

电沉积RE-Ni-W-P-SiC复合镀层的硬度与耐磨性研究

研究了RE Ni W P SiC复合镀层的硬度与耐磨性。结果表明 ,随着加热温度的提高 ,复合镀层的硬度和耐磨性增加 ,在 4 0 0°C时达峰值 ;温度继续升高 ,复合镀层硬度和耐磨性呈下降趋势。随着复合镀层中磷含量的增加 ,其耐磨性改善。在4 0 0°C热处理条件下 ,随着热处理时间的延长 ,复合镀层的硬度和耐磨性增加 ,当热处理时间达到 3h时 ,复合镀层硬度和耐磨性达到最佳值。随着镀液中SiC和钨酸钠浓度的增加 ,复合镀层的硬度和耐磨性均增强。

脉冲电沉积RE-Ni-W-P-SiC复合镀层工艺

研究了RE Ni W P SiC复合镀层的脉冲电沉积工艺。结果表明:RE Ni W P SiC镀层的脉冲电沉积速率比直流电沉积大,脉冲镀层的耐蚀性和硬度都优于直流镀层,耐蚀性优于1Cr18Ni9Ti不锈钢;脉冲频率和占空比对镀层的沉积速率、镀层成分以及镀层的性能都有很大影响。脉冲镀层比直流镀层的结晶更细密,表面更光滑平整。稀土的加入有利于细化晶粒。

电沉积RE-Ni-W-P-SiC-PTFE非晶态复合材料的组织及结构

在碳钢表面进行了RE Ni W P SiC PTFE(聚四氟乙烯 )非晶态复合材料镀层的电沉积试验 ,研究了镀液的pH值、电流密度和热处理温度等因素对镀层的组织和相结构的影响 ,确定了电沉积工艺的最佳条件。结果表明 ,镀态镀层以非晶态的形态存在 ,随着热处理温度的升高 ,镀层逐渐向晶态转变 ,Ni3P相的衍射峰逐渐加强 ;在低于4 0 0℃时 ,镀层中含有PTFE相 ,在 4 0 0℃以上时 ,PTFE相已不存在 ,同时镀层中出现了W3O、NiO及 (FeNi)相 ;5 0 0℃时镀层已完全晶化 ,此时的物相组成与 4 0 0℃相近 ,只是W3O相被WO2

电沉积RE-Ni-W-P-SiC复合镀层的腐蚀行为研究

研究了RE Ni W P SiC复合镀层在10%HCl,10%FeCl3,10%H2SO4和40%H3PO4等介质中的腐蚀行为。结果表明,以Ni W P合金为基体的复合材料镀层在镀态或热处理条件下,在硫酸、磷酸、盐酸和氯化铁溶液中具有较好的耐蚀性,其耐蚀性优于316L不锈钢;RE Ni W P SiC复合镀层在硫酸和磷酸溶液中的耐腐蚀性更明显;RE Ni W P SiC复合镀层在硫酸和磷酸溶液中的腐蚀为缝隙腐蚀和晶间腐蚀,而在盐酸和氯化铁溶液中的腐蚀为点蚀和晶间腐蚀。

高硅铸铝表面电沉积Re-Ni-W-P-SiC复合陶瓷镀层

采用合适的除铜、去硅、浸锌等前处理工艺 ,在高硅铸铝表面成功地电沉积一种性能优异的Re- Ni- W- P- Si C复合陶瓷镀层 ,研究了腐蚀时间、浸锌时间对工艺的影响 ,解决了高硅铸铝材料表面难处理等问题。结果表明 ,在浸锌时间为 4～ 5 min时 ,铸铝表面浸锌层效果最好 ,获得的 Re- Ni-W- P- Si C复合镀层硬度高 ,耐磨、耐蚀性能好 ,是一种新型的功能性镀层 ,其镀态硬度为 HV5 0 0～70 0 ,经 40 0℃热处理 1 h,硬度可达 HV1 2 0 0～ 1 35 0 ,磨损率仅为 2 .93mg/cm2 · h-1。高温经热处理后立即浸入冷水中 ,不脱落 ,表明镀层附着力好 ,与基体结合力强。

脉冲与直流电沉积RE-Ni-W-P-SiC复合镀层性能研究

采用脉冲与直流电沉积 ,研究了RE Ni W P SiC复合镀层的性能。结果表明 :在相同的条件下 ,采用脉冲电流得到的复合镀层比直流电流得到的镀层有更高的硬度、沉积速度 ,同时耐磨。

脉冲电沉积RE-Ni-W-P-SiC复合镀层的硬度研究

研究了脉冲条件对脉冲电沉积RE Ni W P SiC复合镀层硬度的影响。结果表明:脉冲频率和占空比的变化对镀层的硬度都有很大的影响;脉冲镀层的硬度都比直流镀层的硬度高;热处理温度小于600℃时,镀层的硬度随温度的升高而升高,加热温度继续升高,镀层硬度呈直线下降;在400℃热处理条件下,随着时间的延长,镀层的硬度增加,当时间达到3h时,镀层硬度最高;镀层中的SiC微粒随着温度的升高和时间的延长向基体金属的扩散越来越多;RE Ni W P SiC脉冲镀层的硬度高于Ni W P SiC脉冲镀层的硬度。

电沉积RE-Ni-W-P-SiC-PTFE复合镀层的耐蚀性研究(Ⅰ)

采用不同浓度的硫酸、磷酸溶液为腐蚀介质,研究了RE-Ni-W-P-SiC-PTFE复合电镀层于镀态下及经不同温度热处理后的腐蚀速率与阳极极化曲线,并与RE-Ni-W-P-SiC复合电镀层的阳极极化曲线进行了比较.结果显示,RE-Ni-W-P-PTFE-SiC复合镀层在硫酸、磷酸溶液中的腐蚀规律基本一致,即在镀态或热处理条件下,随着硫酸或磷酸浓度的增加,其腐蚀速率上升,当硫酸浓度达到10%～20%或磷酸浓度达到40%时,腐蚀速率最高;继续增加硫酸或磷酸浓度,复合镀层的腐蚀速率又降低.阳极极化曲线表明: 200 ℃或500 ℃热处理后复合镀层具有较好的耐蚀性;该镀层热处理后耐蚀性要优于镀态下及热处理后的RE-Ni-W-P-SiC镀层.

工艺条件对电沉积RE-Ni-W-P-SiC-PTFE复合镀层性能的影响

研究了电流密度、镀液温度、pH值和PTFE等对电沉积RE Ni W P SiC PTFE复合镀层性能的影响。结果表明 ,镀态下镀层的硬度在 42 0～ 5 5 0Hv之间 ,当镀液中PTFE浓度为 2 5ml/L时 ,磨损量最小 ,但镀层的耐蚀性却最差 ;而当镀液中PTFE浓度为 30ml/L时 。

电沉积Ni－W－P－SiC复合材料的组织及结构

Ｘ—射线衍射仪测定表明，当Ｎｉ—Ｗ—Ｐ—ＳｉＣ复合镀层中的磷含量大于８ｗｔ％时，镀层在镀态时呈非晶态结构；α—ＳｉＣ微粒的存在并不影响复合镀层的结构，也不参与结构的转变。热处理温度对Ｎｉ—Ｗ—Ｐ—ＳｉＣ复合镀层的组织结构有一定的影响，当温度升到３００～４００℃时，产生Ｎｉ３Ｐ粒子，起到沉淀硬化作用，因此，复合镀层的硬度最高；若继续升高温度，Ｎｉ３Ｐ粒子长大，然后集聚并粗化，导致镀层软化，硬度下降。扫描电镜证明，α—ＳｉＣ微粒在复合镀层中的分布较均匀。添加剂的加入，有利于提高复合镀层的晶化温度。

脉冲电沉积Ni-W-P-SiC复合电镀的研究

研究了脉冲电沉积Ni W P SiC复合电镀工艺。研究表明 :Ni W P SiC镀层的脉冲电沉积速率比直流电沉积的大 ,脉冲镀层的耐蚀性和硬度都优于直流镀层 ,耐蚀性还优于 1Cr18Ni9Ti不锈钢 ;脉冲频率和占空比对镀层的沉积速率、镀层成分以及镀层的性能都有很大的影响。SEM观察表明 ,脉冲镀层比直流镀层的结晶更细密 ,表面更光滑平整。

(Ni-W-P)-SiC复合镀层的脉冲电沉积及其耐蚀性

研究了(Ni-W-P)-SiC复合镀层的脉冲电沉积工艺及耐蚀性。结果表明:(Ni-W-P)-SiC复合镀层的脉冲电沉积速率比直流电沉积大,脉冲镀层的耐蚀性优于直流镀层和1Cr18Ni9Ti不锈钢;脉冲频率和占空比对镀层的沉积速率、镀层成分以及镀层的耐蚀性都有较大的影响。

脉冲电沉积Ni-W-P-SiC复合镀层的硬度研究

研究了脉冲电沉积的Ni W P SiC复合镀层的硬度。研究表明,脉冲频率和占空比对镀层的硬度都有很大的影响。脉冲镀层的硬度基本上比直流镀层的硬度高100～200Hv。热处理温度小于600℃时,镀层的硬度随温度的升高而升高,在600℃达到峰值。在400℃热处理条件下,随着热处理时间的延长,镀层的硬度增加,当热处理时间达到3h时,镀层硬度最高。镀层中的SiC微粒随着温度的升高和时间的延长向基体金属的扩散越来越多。