钛合金表面MoS2-Ti/Cu-Ni-In多层固体润滑膜的制备及其抗微动磨损性能

目的改善钛合金表面抗微动磨损性能。方法利用非平衡磁控溅射技术在钛合金表面沉积MoS_2-Ti/Cu-Ni-In多层固体润滑膜,并与MoS_2-Ti与Cu-Ni-In单层固体润滑膜进行对比。利用扫描电镜、显微硬度计、摩擦磨损试验机、表面轮廓仪对固体润滑薄膜的形貌、硬度、抗微动磨损性能、磨痕形貌进行分析测试。结果所制备的Cu-Ni-In单层膜与MoS_2-Ti单层膜结构致密,与基体结合良好,MoS_2-Ti/Cu-Ni-In多层膜交替结构清晰,结构致密。MoS_2-Ti/Cu-Ni-In多层膜的硬度大于MoS_2-Ti及Cu-Ni-In单层膜,多层膜的平均微动系数为0.06,MoS_2-Ti单层膜的平均微动系数为0.102,Cu-Ni-In单层膜的平均微动系数大于1.0。在12 000个微动循环周期后,测得MoS_2-Ti/Cu-Ni-In多层膜的最终磨损总量为0.045 mm~3,Cu-Ni-In单层膜的最终磨损总量为37.79 mm~3,MoS_2-Ti单层膜的最终磨损总量为0.296 mm~3,即多层膜的抗微动磨损性能较Cu-Ni-In单层膜改善了2个数量级,较MoS_2-Ti单层膜改善了5倍以上。结论 MoS_2-Ti/Cu-Ni-In多层膜中的多个界面对单层晶粒生长起到了阻挡作用,从而致使交替结构中的单层晶粒得到细化,Cu-Ni-In膜的引入延缓了MoS_2-Ti膜的剥落及其转移,增加了不锈钢球与多层膜间第三体的润滑及减磨效果,多层膜表现出了优异的抗微动磨损性能。     

褪除液浓度及pH值对电化学法褪除碳化钨-镍涂层工艺的影响

对于返修零件的残余涂层及生产中不合格的碳化钨-镍涂层,必须先去除,才能重新喷涂.为有效褪除涂层,又不破坏基体,采用电化学法褪除45号钢表面的碳化钨-镍涂层,通过研究褪除液浓度和pH值对涂层褪除速率及对基体腐蚀情况的影响,确定最优pH值为11~12,褪除液(主要成分酒石酸钾钠和碳酸钠)质量浓度为0.25kg/L,电流密度为6A/dm2.采用此电化学工艺可有效褪除钢基体表面的碳化钨-镍涂层,也不会对钢基体造成影响.     

Study on properties of Hf6Ta2O17/Ta2O5 system: A potential candidate for environmental barrier coating (EBC)

Ta₂O₅ doped Hf₆Ta₂O₁₇ system (Hf₆Ta₂O₁₇/Ta₂O₅) is considered to have potential application prospect in the field of aero-engine. We herein focus on the thermo-physical, mechanical properties and CMAS corrosion resistance of Hf₆Ta₂O₁₇/Ta₂O₅ to systematically evaluate the possibility for the application of environmental barrier coating (EBC). By changing the content of Ta₂O₅, the gradient adjustment of thermal expansion coefficient can be realized while maintaining low thermal conductivity (1.5–2.2 W/(m·K)). The introduction of Ta₂O₅ significantly reduces the modulus and improves the fracture toughness. Single-phase Hf₆Ta₂O₁₇ shows excellent corrosion resistance against molten calcium-magnesium-alumina-silicate (CMAS). The crystallization of CaTa₂O₆ and HfSiO₄ is the important factor to prevent further corrosion. The introduction of Ta₂O₅ weakens the ability to prevent Si penetration and greatly increases the thickness of the corrosion layer. The results highlight the merit of Hf₆Ta₂O₁₇/Ta₂O₅ system as potential candidate for multi-layer gradient coating on the surface of ceramic matrix composites.     

尖端结构对PS-PVD YSZ涂层沉积的影响

采用等离子喷涂-物理气相沉积(PS-PVD)技术在设计的尖端结构试样表面制备了YSZ涂层,研究了YSZ涂层在尖端不同区域的形貌、厚度、孔隙率和微区力学性能的差异.结果表明:尖端部位各区域涂层呈现羽柱状结构,在涂层生长过程中柱状晶之间会因生长的空间受限而存在“挤压”竞争效应,尖端边角的几何特性会削弱“挤压”竞争效应,因此其涂层厚度远高于尖端其他区域;此外,尖端尖角附近的涂层羽柱状结构呈放射状,并沿基体表面法线方向向上生长;纳米压痕表明涂层硬度由顶部至底部呈现逐渐下降趋势,这与涂层结构和残余应力相关;尖端结构的尖角区域涂层微区硬度,显著高于尖端两侧区域;结合数值模拟分析结果发现,半封闭型面会导致等离子射流紊乱度上升,由于不同方向等离子体存在“卷流”和“冲击”现象,其对应沉积的涂层厚度下降,孔隙率上升.     

脉冲偏压对电弧离子镀TiCN薄膜组织结构的影响

目的改善TiCN薄膜的组织结构,进一步提高其硬度与结合力。方法采用电弧离子镀技术,通过改变脉冲偏压的幅值,制备一系列的TiCN薄膜。通过扫描电子显微镜(SEM)观察薄膜的表面和截面形貌,采用X射线衍射(XRD)对薄膜进行物相分析,用X射线光电子谱(XPS)表征元素的化学状态,通过能谱仪(EDS)分析薄膜的成分。采用显微维氏硬度计测量薄膜硬度,使用3D轮廓仪测量薄膜厚度,利用多功能材料表面性能试验仪进行划痕测试。结果偏压对薄膜的硬度、结合力、组织结构和沉积速度都有影响。随着脉冲偏压的提高,TiCN薄膜晶粒逐渐细化,沉积速率、结合力有先增大后减小的趋势,TiCN薄膜的硬度保持线性提高。偏压为-200 V时,TiCN薄膜出现C_3N_4新相,此时薄膜的硬度和结合力都大幅度提高,表面形貌发生突变,液滴最多。偏压为-250 V时,TiCN薄膜综合性能最好,并且表面的液滴明显减少,此时硬度值为4017HV,结合力为51 N。结论偏压对组织结构及碳元素在薄膜中的存在形式有一定影响,适当地改变脉冲偏压可以使TiCN薄膜的显微组织更加致密,同时,形成的弥散硬化相使薄膜具备较高的硬度和膜基结合强度。     

小型绕线功率电感磁芯材料及其表面金属化工艺研究现状

小型绕线功率电感的主要结构包括磁芯和线圈.目前市场上主要使用镍锌材料和合金材料作为磁芯的主要材料,合金材料作为近年新开发的材料,在各方面性能上有明显的优势.随着合金材料技术的逐渐完善,合金材料将逐渐取代镍锌材料.电极金属化是小型绕线功率电感制作工艺中的重要环节,本文介绍了目前市场上主流的两种电极金属化工艺,比较了其膜系结构以及工艺流程的差异,其中真空镀工艺比电镀工艺在薄膜综合性能及环保要求上具有一定的优势,是未来主流磁芯电极表面金属化工艺.     

不同碳基体CVD SiC涂层的制备及其微观结构研究

分别以高纯石墨、细颗粒石墨及低密度的C/C复合材料为基体,以MTS为SiC的先驱体原料,采用化学气相沉积工艺制备SiC涂层.通过扫描电镜(SEM)观察CVDSiC涂层的微观形貌,利用X射线衍射仪(XRD)分析其晶体结构.研究发现,在不同沉积基体上沉积的SiC晶体形貌不同.以高纯石墨为基体的试样表面基本不存在SiC晶须的生长特征;以细颗粒石墨为基体的试样的表面发现了SiC晶须的生长特征,且基体内部的SiC晶体具有一定的CVI特征,即靠近基体内部沉积的SiC晶体逐渐由SiC晶须变为SiC纳米线;以C/C复合材料为基体的试样内部和表面沉积的SiC晶体表现出多元化的形貌,以层状SiC晶体和SiC晶须为主,主要是由基体材料微观结构的多元化而导致沉积的微区气氛有所不同造成的.     

大气等离子喷涂制备锰钴尖晶石涂层及其电导率

采用大气等离子喷涂(APS)工艺制备了Mn-Co尖晶石涂层,同时研究了不同载气和喷距对涂层形貌及电导率的影响.采用直流四电极法测量涂层的电导率,利用SEM,XRD和XPS等表征手段对涂层微观形貌、组成等进行表征.结果表明,所制备的涂层致密、孔洞较少、与基体结合良好,表面呈现液态沉积与微熔颗粒堆积相混合的状态.800℃时,载气量为2 SLPM下涂层的电导率是18 S/cm,而其余载气量下涂层电导率仅有8 S/cm,低载气量制备的Mn-Co涂层具有良好的导电性;800℃下只有喷距为130 mm的涂层电导率超过了10 S/cm,增加喷距对电导率影响较小,各涂层电导率分布较为接近.测试态涂层表面形成了各种取向的金字塔状尖晶石晶体结构,其尖晶石相衍射峰强度显著提高;高电导率涂层中2价和3价元素比例更接近1∶2,为典型的尖晶石结构,其表现出较高的电导率.因此,适当的载气流量和喷涂距离可使涂层中含有更多的高电导率尖晶石相.     

Electrodes modified with Ni electrodeposition decrease hexavalent chromium generation in an alkaline electrolysis process

Alkaline water electrolysis is one of the easiest methods used to produce hydrogen, offering the advantages of simplicity and low cost. The challenges for the widespread use of water electrolysis are to reduce energy consumption, cost and maintenance and to increase the reliability, durability and safety of the process. The alkaline electrolysis of water has been used for many years to obtain H₂ and O₂; however, less expensive, more active, endurable and efficient electrodes must be designed. Stainless steel (SS) is considered one of the least expensive electrode materials for alkaline electrolysers, since it is relatively chemically stable and has a low overpotential. Nevertheless, SS anodes do not withstand high concentration alkaline solutions because they undergo a corrosion process. If the electrolyser operates at a voltage of up to 1.6 V, it can generate Fe₃O₄ and hazardous hexavalent chromium (Cr⁶⁺) at the anode. Hexavalent chromium is generated when the chromium-containing stainless steel electrodes undergo an electro-oxidation process. In this work, a low power alkaline electrolyser was designed. In the first step, six electrodes were manufactured of stainless steel. In the second step, a nickel layer with matte or opaque finish was deposited on the SS surfaces to improve their resistance to corrosion and wear. Then, the performance curves and the production of hexavalent chromium were determined. The performance curve after 70 h of operation with nickel-plated electrodes showed an overpotential of 0.5 V at 10 A compared with stainless steel electrodes. Cr⁶⁺ was detected in the electrolyte and bubbler water of the system using SS electrodes at values that exceeded the standard (>0.5–1 mg L⁻¹). If the electrolyser used Ni-electrodeposited electrodes, Cr⁶⁺ was observed in quantities within the normal range (<0.1 mg L⁻¹). It is very important to prepare modified anodes with nickel electro-deposited, this process prevents the generation of hexavalent chromium, contamination of the electrolyte and reduces maintenance times. The above compensates the slight increase in electrodes cost and energy consumed by the electrolyser.     

镀铝表面改性7YSZ纳米热障涂层热震性能分

为提高7YSZ纳米热障涂层的热震性能, 实验中采用超音速火焰喷涂(HVOF)在涡轮叶片模拟工件上制备了粘结层NiCrCrAlYTa, 再使用大气等离子喷涂(APS)在粘结层上制备了7YSZ纳米陶瓷层。采用磁控溅射在7YSZ热障涂层样品表面镀铝, 并在不同压力下(200、250、300 Pa)对镀铝样品进行热处理表面改性。对喷涂态样品和镀铝改性后样品进行水淬热震实验, 1050℃保温10 min+水冷5 min为一个热循环, 观察热障涂层镀铝改性前后样品在水淬热循环过程中形貌和结构演变。实验结果表明, 镀铝改性后样品表面存在铝薄膜蒸发、凝固后形成的疏松纳米Al晶粒表层以及由Al和ZrO₂原位反应形成的致密α-Al₂O₃底层。在镀铝样品热处理过程中, 随着压力升高, 疏松层致密度逐渐增加。不同热处理压力下镀铝表面改性后样品经过73次水淬热循环后剥落面积均小于喷涂态样品, 显示出良好的抗热震性。