優(yōu)化大氣等離子噴涂工藝,降低TBC(熱障涂層)生產(chǎn)成本.doc

資料收集于網(wǎng)絡(luò) 如有侵權(quán)請聯(lián)系網(wǎng)站 刪除 謝謝 TBC coating cost reduction by optimization of the Atmospheric Plasma Spray process 優(yōu)化大氣等離子噴涂工藝，降低TBC（熱障涂層）生產(chǎn)成本S. Mihm, T. Duda, Birr / CH, G. Thomas, H. Gruner, Mgenwil / CH and B. Dzur, Ilmenau / DThe global economic growth has triggered a dramatic increase in the demand for resources over the last few years, resulting in steady price increases for energy and raw materials. In the gas turbine manufacturing sector, process optimizations of cost-intensive production steps involve a heightened savings potential and form the basis for securing future competitive advantages in the market economy.全球經(jīng)濟增長在過去的幾年中引發(fā)了對資源需求急劇增加，導致能源和原材料價格穩(wěn)步上漲。在燃氣輪機制造業(yè)，對成本密集的生產(chǎn)工藝優(yōu)化具有成本節(jié)約的潛力并能為企業(yè)在將來市場經(jīng)濟的競爭中打下堅實的基礎(chǔ)。In this context, the atmospheric plasma spraying (APS) process for thermal barrier coatings (TBC) has been optimized. A constraint for the APS coating process optimization is the use of the existing coating equipment.在這樣的大背景下，熱障涂層（TBC）的大氣等離子噴涂（APS）工藝得以改進優(yōu)化。而APS制備涂層工藝優(yōu)化的一個限制條件在于現(xiàn)有涂層設(shè)備的使用。Furthermore, the current coating quality and characteristics are not allowed to change in order to avoid new qualification and testing.此外，為了避免重新申請資質(zhì)以及進行額外測試，還不能改變當前的涂層質(zhì)量和性能。Using experience in atmospheric plasma spraying and empirically gained data, the process optimization plan included the variation of e.g. the plasma gas composition and flow rate, the electrical power, the arrangement and angle of the powder injectors to the plasma jet, the grain size distribution of the spray powder and the plasma torch movement procedure like spray distance, offset and iteration. In particular, plasma properties (enthalpy, velocity, temperature), powder injection conditions (injection point, injection speed, grain size distribution,) as well as the coating lamination (coating pattern, spraying distance) are examined. The optimized process and resulting coating was compared to the current situation by several diagnostics methods.在以往大氣等離子噴涂經(jīng)驗和日常獲取的寶貴數(shù)據(jù)基礎(chǔ)上，我們的工藝優(yōu)化計劃包括一系列的改變，如等離子氣體組成，流量；用電，布局及粉末注入等離子流的角度，粉末的粒徑分布、等離子槍的移動（如噴距、偏差以及重復性等）。特別是等離子性能（焓值、速度以及溫度），注粉條件（注粉點、注粉速度、粒徑分布），以及還有涂層（涂層形式，噴涂距離）等方面做了重點研究。我們將優(yōu)化后的工藝及其所制備的涂層與當前普遍使用的幾種工藝采用不同的分析方法進行了對比。The improved process provides significantly lower costs by achieving the requirement of comparable coating quality. Furthermore, a contribution was made to a better comprehension of the atmospheric plasma spraying of ceramics and a method for future process developments was defined.在同等涂層質(zhì)量的前提下，優(yōu)化后的工藝能很大程度的降低生產(chǎn)成本。此外，我們對大氣等離子陶瓷粉末噴涂過程做了一些詳細描述，使其更加通俗易懂，同時，我們還了未來工藝的研發(fā)方法。1 Introduction 引言Plasma coated thermal barrier coatings (TBC) are successfully established in the gas turbine manufacturing business since the seventies 1. In the hot gas section of gas turbines TBCs fulfill the functions of thermal insulation, therefore lowering the temperature of the metallic portion of the part. Firing temperatures in the combustion chamber above 1300C and limited long term operation temperatures of approx. 950C for the metallic materials resulting in high requirements to coating systems on blades, vanes and combuster parts.從上世紀七十年代起，采用等離子技術(shù)制備的熱障涂層（TBC）成功應用到燃氣輪機制造業(yè)。在燃氣輪機的熱燃氣領(lǐng)域，熱障涂層滿足了隔熱的要求，從而降低了工件金屬部分的溫度。燃燒室的燒結(jié)溫度超過1300攝氏度，而大部分金屬材料的長期工作溫度在950攝氏度左右，這樣一來，就勢必導致旋片，小葉片以及燃燒室部件在噴涂時的高要求。Typical thermal barrier coatings are multi-layer systems based on a duplex structure, a dense metallic bond coat layer (material: MCrAlY, M-Ni and/or Co) and a porous ceramic top coat layer (material: YSZ, yttrium-stabilized zirconia), shown in Fig. 1.典型的熱障涂層是一個以復式結(jié)構(gòu)為基礎(chǔ)的多層系統(tǒng)，包括致密金屬結(jié)合涂層（材料如：MCrAlY, M-Ni和/或Co），以及上層多孔陶瓷涂層（材料如：YSZ, 釔穩(wěn)定氧化鋯），如圖1所示。Fig. 1. plasma coated TBC-coating system on turbine blade圖1：輪機葉片上的熱障涂層系統(tǒng)（等離子制備）The dense MCrAlY coating protects the base material against corrosion/oxidation and provides the connection for the ceramic top coat. The porous ceramic top coat functions in connection with the external and internal component cooling as a thermal barrier. Contrary to the dense MCrAlY coating a defined porosity of the YSZ coating is necessary to compensate strain difference and to reduce thermal conductivity. These specific requirements pose a challenge to the technology for producing such coating systems. MCrAlY致密涂層對母材起到了抗氧化防腐蝕作用，并同時實現(xiàn)了與表面陶瓷涂層的連接。表面多孔陶瓷涂層一來用于與里面的涂層相連，也為其所覆蓋的內(nèi)部部件形成了一個熱障礙層，起到了冷卻的作用。相對于MCrAlY致密涂層而言，固定孔隙率的YSZ涂層對拉力差異補償及降低導熱率來說是非常必要的。而這些特殊要求就對當今涂層生產(chǎn)技術(shù)提出了新的挑戰(zhàn)。In addition to ensure coating quality, the manufacturing costs are more and more in focus of current developments.除涂層質(zhì)量外，制造成本也越來越成為了當前發(fā)展的焦點問題。The production of porous YSZ coatings is done by Atmospheric plasma spraying (APS). Using this technology the plasma torch construction is one limiting factor for process improvements. For example voltage and power fluctuations influence the particle properties negatively 2, 3, 4. The use of cylindrical nozzle design limits the possibility of adjusting the plasma flow. By several new plasma torch concepts (multi-electrode, cascade, high power 5, 6, 7, 8) new characteristics are achieved which can contribute to a reduction in manufacturing cost. The traditional single-cathode-anode plasma torch based on F4/MC60 is the most widely-used system for years. Especially in turbine manufacturing this system is used for coating components with complex geometries and according to this targeted product extensive manipulation sequences of the plasma torch is required.多孔YSZ涂層通過大氣等離子工藝（APS）進行噴涂。而采用該項技術(shù)進行工藝改造的關(guān)鍵限制因素是等離子槍的設(shè)計制造。如電壓和電流的波動會影響到粉末顆粒的性能2, 3, 4。圓柱形噴嘴的使用限制了等離子流調(diào)整的可能性。通過采用一些新的設(shè)計理念（如多電極、串聯(lián)方式，大功率等5, 6, 7, 8），等離子噴槍開發(fā)了一些新的性能，從而能達到降低生產(chǎn)成本的目的?；贔4/MC60基礎(chǔ)上制造的傳統(tǒng)單陰陽極等離子噴槍系統(tǒng)已經(jīng)廣泛推廣并使用多年。特別是在輪機制造行業(yè)，該系統(tǒng)用于復雜工件的噴涂，因為工件結(jié)構(gòu)復雜，等離子噴槍的安裝工序就更繁雜一些。 For the coating process of turbine components with porous YSZ coating and a porosity class of 15%, the manufacturing costs excluding wear parts for a depreciated equipment like F4 with typical coating parameters are shown in Fig. 2.輪機部件的YSZ多孔涂層噴涂工藝（孔隙率大于15%）的成本計算在圖12中做了圖示說明，采用典型參數(shù)進行噴涂，費用中不包含部件磨損和F4這樣的設(shè)備折舊費用。Fig. 2. cost allocation of APS process for porous YSZ coating, excluding wear parts anddepreciated equipment 圖2：采用APS工藝制備多孔YSZ涂層的成本計算圖，部件磨損及設(shè)備折舊費用不在計算范圍內(nèi)Plasma parameters with a total gas flow rate 30 slpm and an argon/hydrogen ratio of 4:1, as well as a electrical power of 30 kW result by a powder feed rate of 80 g/min in deposition efficiency (ratio of deposited powder weight to feeded powder weight = DE) of about 35%. In relation to current costs of employee, electricity, gases and powder, the YSZ powder usage is the major cost factor of the coating process. The increase in process efficiency by using the existing equipment with no change of coating quality (porosity, porosity distribution, coating thickness, stress, thermal-shock stability) is beneficial because no additional investment costs occur and a high degree of experience in handling the equipment is retained. A parallel use of already qualified coating processes with the existing equipment is possible as well. In this context an improvement of the plasma torch equipment based on a single-cathode-anode system with subsequent coating parameter optimization is done. Target is to realize a more efficient process with increased effective coating deposition. 等離子參數(shù)為：燃氣總流量30 slpm，氧氣/氫氣比率為4:1，功率小于30kW，這是因為35%左右的沉積效率（粉末沉積重量除以送粉重量的比率=DE，送粉率）的送粉速度為80g/min。按照目前的人工、用電、燃氣和粉末成本，YSZ粉末無疑是噴涂過程中的主要成本因素。通過使用現(xiàn)有噴涂設(shè)備，涂層質(zhì)量保持不變（孔隙率、孔隙率分布、涂層厚度、應力、熱震穩(wěn)定性）的前提下，提高噴涂效率是非常有益的，因為并沒有產(chǎn)生額外的成本，并且工人以往積累的設(shè)備操作經(jīng)驗也得以保留。更難能可貴的是，它并不影響在現(xiàn)有設(shè)備上使用以往的噴涂工藝。在這樣的背景下，在單陰陽極系統(tǒng)上進行的噴槍改造以及噴涂參數(shù)優(yōu)化工作得以進行。優(yōu)化目標是通過增加涂層有效沉積率，從而達到提高生產(chǎn)效率的目的。2 Experimental Work 試驗工作2.1 Motivation 試驗動機The current coating process is based on the commercially widely spread single-cathode-anode system, such as F4/MC60. Assuming that a slow, high enthalpy plasma jet is necessary to produce a porous YSZ coating, the used equipment (plasma torch) with a cylindrical nozzle design (diameter 8mm) and a total gas flow rate less than 30 slpm is not optimal. A realized deposition efficiency of 35% leads to high powder consumption, increased coating times and results in high costs. Furthermore, due to the asymmetric plasma jet, the powder injection has to be adapted every production setup and adjusted to the plasma jet. Initial setup tests like spray spot analysis and coating of test parts for process controlling are needlessly complicated and cause high work load before production start and lead to additional costs.當前使用的涂層工藝是在商業(yè)上廣泛推廣的單陰陽極系統(tǒng)，如F4/MC60。假設(shè)制備多孔YSZ涂層時，需要慢速高焓值的等離子射流，那么以往總量小于30 slpm的燃氣流量以及圓柱形噴嘴設(shè)計（直徑為8mm）的設(shè)備（等離子噴槍）就不是很理想了。如果要達到35%的沉積效率，就意味著粉末用量增加，噴涂時間延長，并最終導致噴涂成本升高。此外，由于等離子流不對稱，注粉時不得不調(diào)整工裝以及粉末注入等離子流的角度。在正式生產(chǎn)前進行的初始工裝測試，如噴涂點分析，對測試部件噴涂所做的工藝控制都造成了不必要的復雜以及高強度工作，從未最終導致了成本上升，費用增加。In order to simplify the setup procedure and to achieve time savings, a stable and consistent plasma jet is needed.Consequently, two main targets for optimization of the coating process can be defined.1. Improve of deposition efficiency of the coating process (to reduce the manufacturing costs)2. Generate a stable and consistent plasma jet (impact on indirect added value)One opportunity to influence process stability and plasma properties is the adjustment of the anode design which is functioning as a nozzle. Former investigations with different nozzle designs show a potential to increase the efficiency of the atmospheric plasma spraying 9.Based on these findings a new nozzle design was developed, which is adapted to the required boundary conditions for coating process of turbine components (minimum spray distance). This new nozzle configuration(VMT-nozzle) the basis for the following process optimization.為了簡化工裝并節(jié)省時間，等離子射流必須要穩(wěn)定并連續(xù)。這樣一來，涂層工藝優(yōu)化的兩大目標由此可以得到確定：1. 提高涂層工藝的沉積效率（降低生產(chǎn)成本）2. 制造連續(xù)穩(wěn)定的等離子射流（影響間接附加值）影響生產(chǎn)穩(wěn)定性以及等離子性能的其中一個方式是調(diào)整對陽極的設(shè)計（陽極作為噴嘴使用）。以往改變噴嘴設(shè)計的研究表明了通過此方法提高大氣等離子噴涂效率的可能性【9】。在此基礎(chǔ)上，我們設(shè)計了一個新型噴嘴，該新型噴嘴能很好的適應葉片部件的邊界噴涂（最小噴距）。而該噴嘴的配置（VMT-噴嘴）是接下來工藝優(yōu)化的前提和基礎(chǔ)。2.2Optimization approach 優(yōu)化過程Previous studies show a conflict between increasing the deposition efficiency and the need of a consistent coating porosity 10. By increasing the number and density of molten particle in the spray stream, the coating density increases and the required porosity decreases. Themain influencing factores are consequently temperature, velocity and distribution of particles in the spray stream. To realize an increased DE a possible approach is a holistic examination of the coating process, described in Fig. 3.之前的研究總是會在提高沉積效率和保持一致的涂層孔隙率之間相互矛盾【10】。通過在等離子射流中增加熔融顆粒的數(shù)量和濃度，可以達到涂層密度和孔隙率降低的目的。而主要的影響因素是等離子射流中粉末顆粒的溫度，速度以及粒徑分布。為了提高沉積效率，一個可行的辦法是按照圖3的程序?qū)φ麄€噴涂工藝進行全面的檢查。Fig. 3. plasma coating process, using a single- cathode-anode system (e.g. F4 /MC60)圖3：采用單陰陽極系統(tǒng)（如F4 /MC60）進行的等離子噴涂示意圖， Potential influencing variables of the coating process optimizations are (elected):等離子噴涂工藝優(yōu)化的潛在影響因素（選定的）a) Adjustment of plasma properties:Plasma enthalpy, -velocity, -viscosity, -density, - temperature modified byplasma gases, electrical power, voltage, voltage fluctuationsa) 等離子性能的調(diào)整：下列因素可以改變等離子焓值、速度、粘度、濃度、溫度：等離子氣體 電流、電壓、電壓波動b) Adjustment of particle properties: Particle grain size distribution, particle velocity, temperature modified by powder feedrate carrier gas flow injection conditionsb)粉末顆粒性能的調(diào)整: 下列因素可以改變粉末顆粒的粒徑分布、速度以及溫度：送粉率 載氣流量 注粉情況c) Adjustment of coating deposition:Coating thickness, -porosity, - porosity distribution modified byspray distancemovement procedurerobot velocity, offset, number of layersc)涂層沉積的調(diào)整：下列因素可以改變涂層厚度、孔隙率以及孔隙分布情況：噴距行走程序機器人速度、偏差以及噴涂遍數(shù)1.3Experimental procedure 試驗程序The first step of the optimization process focuses on increasing the deposition efficiency. The analysis are carried out by coating static spray spots. The second step involves an adaption of the coating properties (porosity/porosity distribution) and is realized by coating strings. A string is a coating which is produced by a vertical movement of the robot (constant robot speed) with no horizontal offset and therefore with no overlapping of paths. 工藝優(yōu)化的第一步就是提高沉積效率。研究分析是在固定噴涂點上進行的。第二步則是改變涂層性能（孔隙率/孔隙率分布）并通過涂層列來實現(xiàn)。涂層列是指通過機器人（機器人速度恒定）垂直運動來進行噴涂所制備的涂層，無水平偏差，因此不會產(chǎn)生涂層重疊的情況。Test series a) Adjustment of plasma properties:test objects = spray spotsDevelopment target = increasing of DE to maximum 試驗A系列) 等離子性能的調(diào)整 試驗對象=噴涂點 試驗目的=將沉積率提高到最大值By a theoretical assumption that the particle velocity should be slow as possible to generate a high porous coating, it is necessary to reduce the total gas flow rate to a minimum. Furthermore a high temperature of the plasma jet is favoured to raise the percentage of molten particles and through this an increasing of deposition efficiency. This fact is influenced by changing the content of molecular gas (hydrogen) in the plasma. The test series to optimize DE are done by constant coating distance, constant electrical power, constant powder feed rate.從理論上假定，如果需要制備多孔涂層，則粉末速度需要越慢越好，如降低粉末速度，則總?cè)細饬髁勘仨氁抵磷畹?。另外，等離子射流的溫度越高，粉末熔融的比率就會越高，這樣一來，沉積率也相應得到提高。但改變等離子流中分子氣體（氫氣）含量可以影響該情況。通過恒定噴涂距離、恒定電流以及恒定送粉率來實現(xiàn)沉積率優(yōu)化系列的實驗。The powder feed rate of the standard coating process with 80 g/min has been used. To achieve the minimum coating distance the plasma properties-velocity, temperature are influenced by varying total gas flow rate and argon/hydrogen ratio. Results of these test series are shown in Fig. 4.標準噴涂工藝使用80g/min的送粉率。為了達到最小的噴涂距離，通過改變氣體總流量以及氬氣和氫氣的比率來調(diào)節(jié)等離子性能（速度和溫度）。該系列試驗的結(jié)果如圖4所示：Fig. 4. influence of argon/hydrogen ratio and total gas flow to DE, P=30kW 圖4: 氬氣/氫氣比率及總氣流對沉積率的影響，P=30kWIn consideration of anode and cathode wear and a limitationof the used equipment,a ratio of argon/hydrogen of 4:1 and a total gas flow rate of 37.5 slpm are chosen. The geometry of the VMT nozzle leads to a reduction of length of the emitted plasma jet compared to the cylindrical nozzle, Fig.5. During the previous tests it becomes clear that the present injection condition of 100 in plasma flow direction is not the optimum for the VMT nozzle.考慮到陽極和陰極的磨損以及所使用設(shè)備的限制，選擇4:1的氬氣/氫氣比率，氣體總流量為37.5 slpm。如圖5所示，相對于圓柱形噴嘴，我們設(shè)計的幾何形狀的VMT噴嘴減小了等離子流發(fā)散的長度。按照之前的試驗結(jié)果，目前的100度并不是VMT噴嘴的最佳注入角度。Fig. 5. Images of plasma jets standard (top) vs. optimized (button)圖5：標準等離子流（上圖）與優(yōu)化后的等離子對比效果圖（下圖）Due to this the powder injection point is placed closer to the nozzle exit, the injection angle is changed from 100 to 90 in flow direction. The result is a longer exposure time of particles in the plasma jet resulting in an enhanced melting behaviour, the DE increases from 28% to 46%.由于這樣的原因，注粉點設(shè)置得離噴嘴出口更近，而注粉角度就從順流方向100度變?yōu)?0度。這樣一來，等離子流中粉末顆粒的暴露時間就會延長，那么粉末熔融情況得以加強，沉積效率從28%增加到46%。For the selected plasma parameter and powder injection condition the DE is optimized related to the adjustment of electrical power, Fig. 6.在選定等離子參數(shù)及注粉條件的情況下，如圖6所示，通過調(diào)整電流達到提高沉積效率的目的。Fig.6. influence of electrical power variations on DE and arc voltage, powder A圖6： 電源調(diào)整對沉積率以及電弧電壓的影響示意圖，粉末AFor the investigated electrical power range the arc voltage is almost constant The associated constant arc lengthindicatesa fixationof the anode attachement (arc) inside the nozzle.In first assumption this effect is caused by the geometry of the nozzle and due to this the specific fluid dynamics of the generated plasma flow. Tab. 1 shows a comparison of specific plasma parameters, standard vs. improved (VMT).按照我們研究的電流范圍，電弧電壓是最穩(wěn)定的。穩(wěn)定的電弧長度表明噴嘴內(nèi)部陽極（電?。┑姆€(wěn)定情況。我們首先假定是幾何形噴嘴對陽極的影響造成的。以及由此產(chǎn)生的等離子流的特殊流動性，表1中是標準噴嘴及改進后的噴嘴（VMT），在特定等離子流參數(shù)下的對比情況。Tab.1 comparison of charcteristical plasma parameters of the standard and optimized process(VMT)表1：標準噴嘴及優(yōu)化噴嘴的等離子性能參數(shù)對比表StandardVMTArgon/hydrogen ratio4:14:1Electrical power kW2737Plasma voltage V5863Voltage fluctuations V2211Thermal efficiency %4249標準噴嘴優(yōu)化后噴嘴氬氣/氫氣比率4:14:1電源kW2737等離子電壓V5863電壓波動 V2211熱效應 %4249Test series b) Adjustment of particle properties:test objects = spray spots and stringsdevelopment target = maximization of DE and porosity adjustment 試驗b系列)顆粒性能調(diào)整:試驗對象=噴涂點及噴涂行 試驗目標=將沉積率增加到最大，并實現(xiàn)孔隙率的調(diào)整Using the optimized plasma- and injection parameters from test series a), the porosity for constant coating distance decreases below the minimal accepted level. To counteract, the porosity is adjusted by optimizing grain size distribution of the spray powder and coating distance. The standard used YSZ powder shows a grain size distribution of -125+22 m (powder A). In order to achieve a higher porosity level, the fine fraction is removed and a grain size distribution of -125+44m (powder B) is determined as the optimum distribution. Furthermore, the coating distance is optimized to 160 mm. By adjusting the grain size distribution, the porosity is increased from 13% (powder A) to a required porosity level of approx. 20% (powder B).采用試驗a系列中的優(yōu)化等離子及注粉參數(shù)，由于恒定噴涂距離的降低，孔隙率得以降到最低可接受水平。為了應對此情況，通過優(yōu)化粉末顆粒的粒徑分布以及噴涂距離，可以對孔隙率進行調(diào)節(jié)。標準工藝中使用的YSZ粉末的粒徑分布范圍為-125+22 m (粉末A). 為了達到更高的孔隙率水平，去掉較細顆粒部分，我們決定采用-125+44m（粉末B）作為優(yōu)化后的粒徑分布。此外，優(yōu)化后的噴涂距離為160mm。通過調(diào)整粒徑分布范圍，孔隙率從13%（粉末A）增加到所需的20%左右（粉末B）。Due to the present development results, it is possible to deduce an optimized parameter set for coating of porous YSZ with specific porosity level.按照目前的研究結(jié)果，可以推導出通過優(yōu)化參數(shù)設(shè)置，達到Y(jié)SZ涂層所要求的孔隙率水平。To characterize the particle properties (velocity, temperature) of both coating parameters (standard, improved)SprayWatch measurements are carried out. The comparative analysis clarifies a difference in particle velocity: for the optimized coating parameter the velocity is reduced by approx. 10 m/s compared to the standard parameter, Fig. 7. 通過Spraywatch對兩種噴涂參數(shù)（標準及優(yōu)化后的）進行顆粒速度和溫度的測量。分析對比表明顆粒速度的區(qū)別為：如圖7所示，與標準工藝參數(shù)相比，優(yōu)化后噴涂參數(shù)的顆粒速度降低了大概10m/s.The measurements of particle temperatures show similar values for both parameters at specific coating distances, Fi