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. [

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.

Corrosion resistance of electrodeposited RE-Ni-W-P-SiC-PTFE composite coating in phosphoric and ferric chloride

Corrosion rate and anode polarization curves of electrodeposited RE-Ni-W-P-SiC-PTFE composite coating in various concentrations of phosphoric and ferric chloride were researched. The results show that corrosion rate of the composite coatings increases with the increasing concentrations of phosphoric and ferric chloride, and reaches the maximum value when phosphoric concentration is 40% and ferric chloride concentration is 20% (mass fraction, the same below if not mentioned). Anode polarization curves of the composite coatings show that anode polarization current density of the composite coatings heat-treated at 200 ℃ or 500 ℃ is lower than that of other coatings heat-treated at 300 ℃ or 400 ℃, which displays that the composite coatings heat-treated at 200 ℃ or 500 ℃ have better corrosion resistance. Besides, corrosion resistance of the composite coating heat-treated at 500 ℃ is better than that as deposited and RE-Ni-W-P-SiC composite coating heat-treated at 400 ℃, and is also better than that of 316L stainless steel.

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

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Effects of addition of rare earth on properties and structures of Ni-W-B-SiC composite coatings

The effects of rare earth (RE) on the composition, phase structures, surface morphologies and hardness of electrodeposited RE Ni W B SiC composite coatings were discussed. The results show that W and SiC contents in the coatings increase with the increase of RE in the bath. When RE is added in the coatings, the grains are refined and the trend of formation of amorphous coatings is increased. Moreover, the thermal stability of the RE Ni W B SiC composite coatings is enhanced. The hardness of the coatings is increased with the increase of heat treatment temperature, and it reaches the peak value when heated at 400 ℃. Besides, the hardness of the RE Ni W B SiC coatings is higher than that of the Ni W B SiC coatings.

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.

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.

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.

Structure and characteristics of electrodeposited RE-Ni-W-P-B_4C-PTFE composite coatings

Hardness, friction and wear characteristics of electrodeposited RE Ni W P B 4C PTFE composite coatings were studied, and the reason for these fine characteristics was explained in respect of structure. The results show that 1) the structure of RE Ni W P B 4C PTFE composite coatings experiences a transformation process from amorphous to mixture then to crystal as the heat treatment temperature rises; 2) incorporating of B 4C greatly increases the hardness of the coating; 3) the wear resistance of the coating is best with heat treatment for 1?h at 300?℃, which is greatly superior to that of the other traditional coatings.

Characteristics of electrodeposited RE-Ni-W-B-B_4C-MoS_2 composite coating

The high temperature oxidation resistance of RE Ni W B B 4C MoS 2 composite coating, the effects of electrodeposition conditions on the morphologies of the coating and the effect of heat treatment temperature on its hardness, abrasion resistance and phase structure were investigated by using scanning electron microscope(SEM), X ray diffractometer, microhardness tester and abrasion machine. The results show that the oxidation degree of RE Ni W B B 4C MoS 2 composite coating is small when the temperature is lower than 700 ℃, but it increases sharply when the temperature is higher than 700 ℃. The hardness of RE Ni W B B 4C MoS 2 composite coating increases with increasing heat treatment temperature, it comes up to the maximum value at 400 ℃,but it decreases gradually if the temperature rises continuously. The most favourable abrasion resistance was attained after RE Ni W B B 4C MoS 2 composite coating being heat treated at 400 ℃. Without heat treating, it is mainly amorphous and partially crystallized, but wholly crystallized after being heat treated at 500 ℃. RE in the composite coating is in the form of CeO 2 and additions of CeO 2 and B 4C can enhance the thermostability of RE Ni W B B 4C MoS 2 composite coating.

Structure and properties of electrodeposition RE-Ni-W-B-B_4C-PTFE composite coating

The components, surface and cross sectional morphologies, and the effects of heat treatment temperature on phase structure, hardness, abrasion resistance and oxidation resistance of pulse electrodeposition RE-Ni-W-B-B4C-PTFE composite coatings, were all investigated. The results show that W and B contents increase in the RE-Ni-W-B composite coating by using pulse electrodeposition. RE, PTFE and B4C particles can be co-deposited into the Ni-W-B composite coating, but the amount is very little. X-ray diffraction analysis displays that the RE-Ni-W-B-B4C-PTFE composite coating is mainly amorphous, partially crystallized as-deposited, but it turns into crystalline state and PTFE in the coatings will decompose after the heat treatment temperature is higher than 400℃. The hardness of the composite coating increases with increasing heat treatment temperature, it comes up to the highest value at 400℃. The oxidized film mass of the composite coating increases slowly when the oxidation temperature is lower than 500℃, but it increases linearly and sharply after the oxidation temperature is higher than 600℃.

STUDY ON STRUCTURE AND PROPERTIES OF Ni-W-SiC COMPOSITE COATING

The effects of electroplating conditions on the composition of N-W-SiC composite coating were studied; the znfiuence of heat-treatment and nitrocarburization on the microstructure, hardness and wear resistance of the coating were discussed. The results showed that an amorphous composite coating, containing(wt%) 50-55Ni, 42-45.IW and 3.0-7.6SiC, could be electroplated on the matrix. Afier heat-treatment or nitrocarburization the coating crystallized to form some new phases, and the haordness and wear resistance of the composite coating were enhanced retmarkably.

Studies on High Temperature Oxidation of Electrodeposited RE-Ni-W-P-SiC Composite Materials

The oxidation of the Electrodeposited RE-Ni-W-P-SiC Composite materials at high temperature is investigated. The results show that during high temperature oxidation the relationship between the mass change of pure Ni, Ni-W-P, Ni-W-P-SiC or RE-Ni-W-P-SiC coatings and the oxidation time follows a mixed curve, i.e. it is approximately a linear relationship when the oxidation time is less than 60 mins while it is a power function relationship when the oxidation time is over 60 mins. The order for the oxidation rate of the four coatings is Ni> Ni-W-P> Ni-W-P-SiC>RE-Ni-W-P-SiC. The mass change of Ni-W-P, Ni-W-P-SiC or RE-Ni-W-P-SiC coatings increases exponentially with a rise of oxidation temperature. The high temperature-oxidation resistance of RE-Ni-W-P-SiC composite material is 3-4 times than that of Ni-W-P alloy coating. The cross section morphologies and X-ray diffraction patterns indicate that the high temperature-oxidation resistance of RE-Ni-W-P-SiC composite coating is better than any other coatings.

等离子喷涂参数对Ta/W/Sn复合涂层组织性能的影响(英文)

采用等离子喷涂方法在LY12铝上制备了Ta/W/Sn复合涂层。研究了各种工艺参数对涂层材料熔化程度和沉积效率的影响。采用扫描电子显微镜观察了复合涂层的表面及界面,精密机械天平称量涂层的增重,力学拉伸机测量涂层的抗拉结合强度,能谱和化学方法分析涂层的化学成分。结果表明,等离子喷涂工艺可以制作组织致密、厚度均匀的Ta/W/Sn复合涂层;喷涂功率和送粉速率对材料的熔化状态影响较大,在特定喷距范围内喷距的影响则较小。

钛合金表面Ta-W涂层的制备及循环氧化行为

采用电弧离子镀（AIP）在Ti-6.48Al-0.99Mo-0.91Fe（质量分数,%）钛合金表面制备Ta-10W（质量分数,%）涂层。通过扫描电镜（SEM）与能谱（EDS）分析、透射电镜（TEM）分析、电子探针分析（EPMA）,X衍射分析（XRD）,划痕及纳米压痕试验,研究钛合金基体与Ta-W涂层经900℃大气循环氧化前后的物相组成、组织形貌及性能,讨论涂层/基体的氧化行为。结果表明：沉积态Ta-W涂层连续、均匀、致密,由颗粒细小（≤50 nm）的α-Ta（W）堆积成100~250 nm的等轴晶组成,硬度为14.4~15 GPa,与基体的临界载荷为58.5 N;经900℃大气循环氧化后,钛合金表面形成带裂隙的层状Ti O2、Al2O3疏松混合氧化膜,氧化膜明显脱落;Ta-W涂层能明显提高钛合金的抗循环氧化性能,形成以β-Ta2O5为主的致密氧化膜;随着氧化的进行,氧化膜中Ti O2、Al2O3含量增加并出现Al Ta O4、Al WO4相,氧化膜始终保持完整;氧化过程中,基体中Ti、Al元素及涂层中Ta、W元素互扩散,在界面形成Al Ta2、Al2Ta3、Al3Ti、TixW1-x相,O元素扩散并固溶于基体,在近界面基体处形成厚度逐渐增加的富Ta、W、Al、O、α-Ti固溶体（稳定）区,涂层元素向氧化膜和基体扩散而被消耗为其失效的主要原因。

Ta-W合金Si-Cr-Ti-Zr涂层组织结构与氧化行为

采用料浆烧结法在Ta-10W合金表面制备了Si-Cr-Ti-Zr涂层,利用内热法在大气环境下测试了涂层在1 400℃的抗氧化性能,通过扫描电镜、电子探针和波谱分析等手段分析了Ta-10W合金Si-Cr-Ti-Zr涂层氧化前后的微观形貌与组织结构。结果表明:原始涂层呈3层结构,从表面到基体的组织依次为(Zr,Cr,Ti)Si_2→(Ta,W)Si_2→(Ta,W)_5Si_3→Ta合金;1 400℃高温下保持10 h,涂层仍可有效防护钽合金基体不失效;涂层高温抗氧化机理在于形成了致密的(Si,Zr,Cr,Ti)O_2复合氧化膜,有效减缓了氧元素向内扩散的速率。

纯热暴露下Ta-W涂层/钛合金体系稳定性

采用电弧离子镀(AIP)在Ti-6.48Al-0.99Mo-0.91Fe (质量分数,%)钛合金表面制备Ta-10W (质量分数,%)涂层。通过真空热处理试验、X射线衍射分析(XRD)、扫描电镜(SEM)与能谱(EDS)分析、透射电镜(TEM)分析、电子探针分析(EPMA)等方法,研究纯热暴露下Ta-W涂层/钛合金体系的相组成、显微组织形貌、元素分布、界面行为等,评估了体系热稳定性能。结果表明:纯热暴露过程中,Ta-W涂层相组成无明显变化,均由多晶α-Ta(W)组成,其平均晶粒尺寸由沉积态的46 nm小幅增至750℃时的49 nm和950℃时的51 nm,涂层表现出良好的相稳定性;由于元素Ta、Ti在Ta-Ti体系中扩散系数的差异及难熔金属元素Ta、W良好的稳定性,Ta-W涂层/钛合金体系呈现出良好的界面及元素稳定性:涂层中元素Ta、W始终维持在接近沉积态含量水平,无快速扩散、固溶于基体而失效的行为,体系仅在界面形成互扩散层,无空洞、裂纹缺陷和金属间化合物的形成;由于元素互扩散的加剧及涂层元素在α-Ti、β-Ti中的固溶度差异,钛合金基体同素异晶转变温度(ATT)对体系界面和元素稳定性影响明显;纯热暴露过程中,Ta-W涂层有效厚度保持稳定、无明显变化。基于Fick定律,获得550、750和950℃时互扩散层厚度与时间的关系式。

CVD技术制备Ta/W层状复合材料

运用化学气相沉积(Chemical Vapor Deposition,CVD)技术制备了W体积分数分别10%,13%和18%的Ta/W两层层状复合材料,采用金相显微镜(OM)、扫描电镜(SEM)和室温拉伸实验对复合材料的性能进行分析。结果表明:运用CVD技术可以制备W体积分数不同,且密度优于理论密度99.4%的层状复合材料;复合材料中Ta,W层的晶粒均为柱状晶粒,离界面越近,晶粒越细;沉积态复合材料的力学性能优于纯CVD Ta和CVD W;1600℃×2 h的热处理后,复合材料的界面扩散层宽度显著增大,力学性能高于沉积态的力学性能,最高抗拉强度可达660 MPa。

Ta-W涂层/钛合金体系大气气氛脉冲激光烧蚀行为

采用电弧离子镀(AIP)在Ti-6.48Al-0.99Mo-0.91Fe(质量分数,%)钛合金表面制备Ta-10W(质量分数,%)涂层。通过脉冲激光加热试验模拟火药气体烧蚀工况,采用有限元温度场数值模拟、X射线衍射分析(XRD)、扫描电镜(SEM)与能谱(EDS)分析等方法,研究Ta-W涂层/钛合金体系大气气氛循环热加载烧蚀行为。结果表明:脉冲激光加热过程中,高熔点、高热导率(相比纯钛)Ta-W涂层吸收、富集热量对钛合金基体具有热障保护作用,经10~40 s加热,Ta-W涂层使加热区熔透深度从无涂层基体的190~250μm明显减少至125~180μm,非加热区平均温度从无涂层基体的350~900℃大幅降低至250~500℃。由于加热区边缘温度低、温差大、熔体流动性差,利于孔洞及低熔点Al元素富集区的形成,在循环热应力作用下,该区域易成为表面横向和纵向裂纹策源地。钛合金基体加热后熔化层成分偏析严重,形成富Al带、富Mo和Fe区,在循环热应力作用下,富Al带成为截面横向裂纹的策源地;Ta-W涂层试样加热后形成熔化层、熔合层、扩散层组成的微观组织,热时间延长而尺寸逐渐变小的Ta-W涂层颗粒散布于熔化层导致涂层元素富集于此而起到持续保护作用。由于涂层与基体元素互扩散在熔合层形成孔洞(带),在循环热应力作用下,孔洞(带)为起源于表面加热区边缘的截面纵向裂纹的扩展提供便捷路径,且随加热时间(热震次数)的增加,裂纹尺寸增大,并可导致富Ta-W元素层的剥落而失效。热熔化及循环热应力为Ta-W涂层/钛合金体系大气气氛脉冲激光烧蚀失效的主要因素。

结构钢电沉积Co-W/CeO_(2)复合镀层及其性能研究

选择CeO_(2)颗粒作为复合相,利用电沉积技术在普通结构钢表面制备出Co-W/CeO_(2)复合镀层,并研究镀液中CeO_(2)颗粒浓度对复合镀层的微观形貌、化学成分、结合力、硬度、耐磨性能以及高温抗氧化性能的影响。结果表明:Co-W/CeO_(2)复合镀层与基体结合牢固,表面分布着类似胞状的晶粒团聚体,其化学成分为Co、W、Ce和O元素。随着镀液中CeO_(2)颗粒浓度从2 g/L升高到15 g/L,复合镀层的晶粒团聚体尺寸差异先减小后增大,吸附在晶粒团聚体表面及边界处的CeO_(2)颗粒量先增多后减少,导致复合镀层的硬度、耐磨性能和高温抗氧化性能都呈先增强后下降的趋势。当镀液中CeO_(2)颗粒浓度为8g/L时,Co-W/CeO_(2)复合镀层的晶粒团聚体大小较为均匀,具有良好的致密性,其表面粗糙度仅为0.39μm。该复合镀层的硬度较Co-W合金镀层增大约76 HV,表现出良好的耐磨性能和高温抗氧化性能,摩擦系数和氧化增重量仅为0.43和0.74mg/cm^(2)。