直流电弧热喷涂等离子体偏离局域热力学平衡态分析

在大气压力下,利用直流电弧放电产生热喷涂等离子体,采用发射光谱和热焓探针对热等离子体的射流特性进行诊断。文中通过使用氩原子两条特征谱线的辐射强度,采用双谱线相对辐射强度比值法来计算等离子体的电子温度;同时使用焓探针测量等离子体射流的焓值来计算得到气体温度。研究不同氩气流量和电流强度下,热等离子体的气体温度与射流中电子温度的演变情况,并对两者温度差值出现的原因及变化情况进行分析。结果表明,相同条件下发射光谱法测量的电子温度始终高于焓探针测量的等离子体温度,热喷涂等离子体在一定程度上偏离局域热力学平衡态。     

热喷涂技术的过去,现在和将来

首先回顾了热喷涂技术的发展史。然粕分析对比各种热喷涂工艺的特点及其市场分配情况。叙述了热喷技术当前明面临的主要问题和进展，末尾介绍了热喷涂技术在各种工业中的应用情况。     

热喷涂技术的过去、现在和将来

首先回顾了热喷涂技术的发展史。然后分析对比了各种热喷涂工艺的特点及其市场分配情况。叙述了热喷涂技术当前面临的主要问题和进展,末尾介绍了热喷涂技术在各种工业中的应用情况。     

焊接电弧等离子体热学特性测量方法的研究进展

测量焊接电弧等离子体的温度、粒子密度等参数,有助于深入理解和研究焊接电弧等离子体的物理性质,从而为寻找提高焊接质量、改善焊接工艺的新途径提供了基础数据。文中介绍了几种常用的接触法和非接触法的使用原理和工作特点,比如Langmuir探针法、热电偶法、光学干涉法、光谱分析法等,着重介绍了焊接电弧等离子体的光谱理论原理和几种光谱测量方法,主要阐述和分析了计算焊接电弧温度场的三种方法的测量原理和优缺点,如标准温度法、谱线相对强度法(双线法、Boltzmann作图法)和谱线绝对强度法,这三种方法使用的条件和焊接环境各不相同。这些计算方法有助于测量焊接电弧等离子体的温度场分布,有助于在实际研究过程中选择合适的等离子体测量方法和计算手段。     

电感耦合等离子体发射光谱法测定氟钽酸钾中十四种杂质元素

提出了基体匹配标准曲线 ,电感耦合等离子体发射光谱法直接测定氟钽酸钾中十四种杂质元素的分析方法。本方法各元素测定的相对标准偏差小于 10 % ,回收率在 90 %～ 110 %之间 ,测定下限除 Si外分别小于或等于 0 .0 0 0 5 %。     

热喷涂技术的研究进展

从喷涂设备、涂层应用和质量监控方面综述热喷涂技术的发展现状,重点介绍了等离子喷涂、超音速电弧喷涂、超音速火焰喷涂以及冷喷涂技术的最新进展;提出了制备热障、纳米、非晶、超导及隐身功能涂层将成为研究热点;指出利用各种先进的声、光、电、磁无损检测技术,对涂层性能进行在线诊断、评估质量和预测寿命的研究方向;并对热喷涂技术的发展趋势进行了展望.     

光谱诊断辅助水下湿法焊接等离子体成分计算

对水下湿法焊接等离子体成分的计算一直很少,文中通过搭建水下湿法焊接试验平台,对电弧光谱信息进行采集分析,根据诊断的结果及气泡成分的研究,确定了计算中所考虑的粒子. 在此基础上,通过对水下湿法焊接电弧等离子体的平衡方程的分析,基于质量作用定律,选择五种基本粒子,将其它粒子用这五种基本粒子表示,代入守恒方程组,在特定的压力和温度下计算了各个粒子的数密度,这种方法和传统的通过求解Saha方程等守恒方程组得到等离子体粒子数密度不同. 结果表明,不同温度区占据主要成分的粒子不同,对电弧等离子体产生的影响也不同,既可以为进一步研究水下湿法焊接电弧稳定性及焊接质量提供理论依据及基础,也可以和光谱信息结合进行温度计算及主要温度区间的粒子确定.     

降低热喷涂涂层孔隙率的方法

热喷涂的工作原理决定了其涂层孔隙是不可避免的。当涂层用于防腐蚀时,腐蚀介质会通过孔隙到达基体表面,从而造成防护失败。因此,封孔处理是提高涂层防腐蚀性能的重要途径。本文总结了涂层封孔处理的方法,对未来涂层封孔技术进行了展望,并提出一种新的涂层封孔剂——釉。     

热喷涂Al-Si-Fe合金涂层耐磨性的研究

采用热喷涂与热化学反应法在AM50表面制备涂层.采用热震实验测试了涂层的结合性,利用X射线分析了涂层以及基体的物相组成,利用ML-100磨损试验机测试了涂层的耐磨性.结果表明:涂层中含有Al8Si6Mg3、Al32lSi..47、Al9Fe0.84Mn2.16Si、Al3.2Fe等第二相;含有过渡层的涂层与基体结合性比不含过渡层的涂层好;采用普通热喷涂工艺制得的涂层与AM50基体相比,耐磨粒磨损性能提高了2倍,黏着磨损性提高了1.7倍.     

热喷涂技术的发展和应用

主要介绍了热喷涂的基本方法、设备、材料和涂层特性;以及当前的发展动态和应用情况;并简要介绍了应用研究的前景.     

High-power hybrid plasma spraying of large yttria-stabilized zirconia powder

To testify to the advantage of large ceramic powder spraying, numerical simulations and experimental studies on the behavior of large yttria-stabilized zirconia (YSZ) powder in a high-power hybrid plasma spraying process have been carried out. Numeric predictions and experimental results showed that, with the high radio frequency (RF) input power of 100 kW, the most refractory YSZ powder with particle sizes as large as 88 μm could be fully melted and well-flattened splats could be formed. A large degree of flattening (ξ) of 4.7 has been achieved. The improved adhesive strength between the large splat and the substrate was confirmed based on the measurement of the crack density inside of the splats. A thick YSZ coating >300 μm was successfully deposited on a large CoNiCrAlY-coated Inconel substrate (50×50×4 mm in size). The ultradense microstructure without clear boundaries between the splats and the clean and crack-free interface between the top-coat and the bond-coat also indicate the good adhesion. These results showed that highpower hybrid plasma spraying of large ceramic powder is a very promising process for deposition of highquality coatings, especially in the application of thermal barrier coatings (TBCs).     

电热爆炸喷涂和等离子喷涂联合法制备热障涂层的研究

采用电热爆炸喷涂和等离子喷涂联合制备热障涂层,以电热爆炸喷涂法在DZ125合金表面制备NiCoCrAlY粘结层,以等离子喷涂技术制备陶瓷顶层。利用扫描电镜(SEM)和X射线衍射(XRD)仪对所制备的粘结层进行分析,结果表明:电热爆炸喷涂的粘结层与基体结合良好,喷涂态的粘结层的相主要由Ni3Al组成。采用联合法制备的热障涂层,在喷涂态的陶瓷层、粘结层、基体3者结合良好,界面清晰。在高温热循环过程中,粘结层/陶瓷层界面间生成了连续、致密的Al2O3膜,阻碍粘结层的氧化。粘结层/TGO界面产生平行于界面的裂纹,是导致热障涂层失效的主要原因。     

粒度调控对钨阴极表面发射微区的影响

为了在微米尺度探究未分级钨粉、分级钨粉制备钨基体在阴极热电子发射性能上的差异,深入了解阴极表面微区电子发射过程和阴极发射机理,本文采用新型深紫外激光发射电子显微镜/热发射电子显微镜系统（DUV-PEEM/TEEM）对两种钨粉制备的阴极表面进行了光电子、热电子成像分析。结果显示,与未分级钨粉相比,分级钨粉制备钨基体的显微组织更加均匀,且闭孔率由1.44%降至0.47%;光电子+热电子联合成像精确得出两种阴极的发射均主要集中于孔隙及孔隙中的活性物质上;通过热电子图像对比及分析,分级钨粉制备阴极的热电子发射微区面积更大、分布更均匀;且在1050℃工作条件下,分级钨粉制备阴极的脉冲电流密度为30.79A/cm2,发射斜率为1.38;综合分析显示其具备更理想的本征热电子发射能力和发射均匀性,这对于了解阴极发射性能及改善热阴极制备工艺有一定的指导作用。     

提高等离子喷涂热障涂层隔热性能的方法

为进一步提高等离子喷涂热障涂层的隔热性能,对陶瓷材料的导热理论及热障涂层的热导率进行了研究.提出了包括寻求新型热障涂层陶瓷材料、添加掺杂剂、制备纳米涂层及双陶瓷层热障涂层等能够改善等离子喷涂涂层隔热性能的方法;并指出,采用等离子喷涂技术制备带颜色的稀土锆酸盐纳米双陶瓷层热障涂层,将会进一步改善热障涂层的隔热性能.     

Evaporation of zirconia powders in a thermal radio-frequency plasma

Incomplete evaporation of high-melting solid precursors, such as zirconia (ZrO₂), is a major problem in the application of plasma-flash evaporation processes to powder synthesis and production of high performance coatings. The evaporation of zirconia powders injected into a thermal radio-frequency (RF) plasma is investigated by using optical emission spectroscopy (OES) and laser Doppler anemometry (LDA) to study evaporation rates and particle velocities. Model calculations are compared with the results of the process diagnostics. Axial emission profiles confirm the influence of the particle size on the evaporation behavior. Line-integrated side-on emission profiles are used to assess the rate of evaporation.     

Thermal Barrier Coatings Made by the Solution Precursor Plasma Spray Process

The solution precursor plasma spray (SPPS) process is a relatively new and flexible thermal spray process that can produce a wide variety of novel materials, including some with superior properties. The SPPS process involves injecting atomized droplets of a precursor solution into the plasma. The properties of resultant deposits depend on the time-temperature history of the droplets in the plasma, ranging from ultra-fine splats to unmelted crystalline particles to unpyrolized particles. By controlling the volume fraction of these three different constituents, a variety of coatings can be produced, all with a nanograin size. In this article, we will be reviewing research related to thermal barrier coatings, emphasizing the processing conditions necessary to obtain a range of microstructures and associated properties. The SPPS process produces a unique strain-tolerant, low-thermal conductivity microstructure consisting of (i) three-dimensional micrometer and nanometer pores, (ii) through-coating thickness (vertical) cracks, (iii) ultra-fine splats, and (iv) inter-pass boundaries. Both thin (0.12 mm) and thick (4 mm) coatings have been fabricated. The volume fraction of porosity can be varied from 10% to 40% while retaining the characteristic microstructure of vertical cracks and ultra-fine splats. The mechanism of vertical crack formation will be described.     

电弧焊极性选择与电弧阴阳极产热关系

极性选择是焊接工艺中最为基础的参数之一,对焊接质量有着重要的影响.通过分析电弧阳极区中性粒子的电离及阴极(或阴极区)的电子发射过程,研究了各种焊接方法下,阴阳极区压降的变化情况和阴阳极的产热.结果表明,时于不同的焊接方法、不同的极性接法(直流正接或直流反接),阴阳极区的电子发射和电离方式并不相同,在特殊情况下会在阴极区...     

TiO2涂层激光热冲击损伤机理研究

研究了等离子喷涂TiO2涂层在激光热冲击条件下激光输出功率对涂层损伤的影响，并探讨了涂层的损伤机理。结果表明，随着激光输出功率的增大，TiO2涂层损伤加剧，当激光输出功率为3900W时被击穿：基体上产生热影响区；TiO2涂层在激光热冲击下的微观损伤形貌主要以放射板条状组织和枝状组织为主，并存在大量的裂纹；TiO2涂层消耗激光能量的方式主要是熔化与再结晶并辅以裂纹的萌生与扩展。     

Superior thermal barrier coatings using solution precursor plasma spray

A novel process, solution precursor plasma spray (SPPS), is presented for depositing thermal barrier coatings (TBCs), in which aqueous chemical precursors are injected into a standard direct current plasma spray system. The resulting coatings microstructure has three unique features: (1) ultra fine splats (1 μm), (2) nanometer and micron-sized interconnected porosity, and (3) closely spaced, through-thickness cracks. Coatings over 3 mm thick can be readily deposited using the SPPS process. Coating durability is excellent, with SPPS coatings showing, in furnace cycling tests, 2.5 times the spallation life of air plasma coatings (APS) and 1.5 times the life of electron beam physical vapor deposited (EB-PVD) coatings. The conductivity of SPPS coatings is lower than EB-PVD coatings and higher than the best APS coatings. Manufacturing cost is expected to be similar to APS coatings and much lower than EB-PVD coatings. The SPPS deposition process includes droplet break-up and material arriving at the deposition surface in various physical states ranging from aqueous solution, gel phase, to fully-molten ceramic. The relation between the arrival state of the material and the microstructure is described.