On-line temperature monitoring and process diagnosis of plasma sprayed coatings On-line temperature monitoring and process diagnosis of plasma sprayed coatings

On-line temperature monitoring and process diagnosis of plasma sprayed coatings

  • 期刊名字:中国焊接
  • 文件大小:545kb
  • 论文作者:Yang Yunzhen,Xia Weisheng
  • 作者单位:College of Automotive Engineering,College of Material Science and Engineering
  • 更新时间:2020-11-11
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论文简介

On-line temperature monitoring and process diagnosis of plasma sprayed coatings21On-line temperature monitoring and processdiagnosis of plasma sprayed coatingsYang Yunzhen and Xia Weisheng杨云珍,夏卫生**Abstract On-line temperature monioring of plasma sprayed coating is presented, which is based on IR pyromelery combinedt0 robot riecories. Temperature fields of the subtrate before spraying and the deposited coating when the damage happensare laken to inestigate the temperature fluctuation informatin. Experimental results demonstrate that coating damage alwaysoccurs in the temperature transition area of the substrate from the higher t0 the lover , as well as the higher temperature area.The temperature diference betoeen the peak and the mean of the relevant regions is beyond 30 -50 C or even higher. Thisase provides the omen of cooting damage and the focusing scopes for the process control of coating temperature in plasmaspraying.Key words plasma spraying, coating temperature , temperature field, coating damage, process diagnosis0 Introductionperature of various areas, the maximum temperature of theCoating temperature is an important factor influencinggiven sample.the formability and quality of plasma spraying coat-ings' -3]. Hence, it is important and necessary to monitor1.2 On-line temperature detecting device and methodand control of coating temperature'4. Up to now, manyThe on-line temperature detecting device is an IR py-efforts have been devoted to measure coating temperatures ,rometer typed Thermalert TX. The pyrometer is fixed onsuch as thermocouple, IR pyrometer'5-n! and infraredthe end arm of a six-axis robot ( Motoman, UP20) andcamera-9. IR pyrometry, as a non-contact and nonde-synchronously moves with the plasma torch. This case pro-structive examination method,' has a wider application forvides the pyrometer the scanning mechanism to enlarge itsits simplicity and practicalityf"0. In this paper, the coat-detecting scope and flexibility. Schematic diagram of tem-ing temperature measurement is performed by an IR py- perature monitoring is shown in Fig. 1.rometer. A thermal imager is also applied to obtain thePlate fixed in thetemperature field, and main efforts are focused on the tem-end arm of robotPlasma gunperature fluctuation when coating damage happens.Pyrometer 'Display and interfacesPlasma jet1 Temperature detecting devices and methodsParticle flux1.1 Detecting device for temperature fieldPLC| AD moduleSubstrateAn uncooled focus plane array ( UFPA) detector isselected to obtain the temperature field. Its sample fre-Data processing and adjustmentof robot spray triectoriesquency is 60 Hz. With the special software, it is possibleand comfortable to analyze the results and calculate tem-Fig. 1 Schematic diagram of temperature monitoring中国煤化工* " The work is supported by the National Natural Science Foundation of C蚌Yang Yunzhen, College of Autonotive Engineering, Wuhan UniversityYHCNMHGs Weisheng, College ofMaterial Science and Engineering, Huazhong University of Science and Technology, Wuhan, 430074. Xia Weisheng, Corresponding author,E-mail: xiaianhust@ hotmail. com22CHINA WELDING Vol. 19 No.3 September 20102 Experimental results and discussionrameters are listed as the set 1 in Table 1.2.1 On-line monitoring of coating temperatureThere are constant repeatable temperature cycles dur-The ceramic substrate of size 120 mm x 80 mm x 15ing spraying process, as shown in Fig. 2. Each cycle re-mm is sprayed with zX. Ni45 powder. Plasma spraying pa-presents a passage throughout the substrate. The period ofTable 1 Plasma spraying parametersPlasma arcPlasma areSprayScanningPowder feedingPreheatedSet No.currentvoltagedistancespeedspaceatetemperature1/ AU/ VH/mm.V/ mm. s-'D/ mmF/g.s-'T/C45050.15030000. 184250248050130200160.343the temperature curveis 19 s, which is the same to that ofare almost the same position for the entire temperaturethe robot scanning cycle. Hence, it is easy to deduce thepeaks and the valleys. The peaks happen in the transitionspray lasting time according to the number of cycles. Theof the z type path due to the heat accumulation with longertemperature curve has a high slope after the beginning oftime being heated by plasma jet.spraying because of the heat input from the plasma jet andthe molten particles. But the slope then begins to slow220一一 Second cycledown after 120s. It is because the thermal transfer coeff-.-Fourteenth ceyelcient and the thermal exchange ability of the sprayed metal180coating are higher than that of the ceramic substrate.When the spraying time is after 300 s, the temperature a160long the scanning passage is almost constant. This is be-140cause the heat exchange is almost dynamically steady a-120mong the plasma power, the specimen and the circum-02468101214161820stance.Spraying time t1sFig.3 Temperature curves of the second and thefourteenth cycles2.2 Process diagnosis of coating damageMild steel plates of size 100 mm x 110 mm x4 mm areselected as substrates. All experiments are based on the05010015020025operating parameters listed as the set 2 in Table 1. Tem-Spraying time I/sperature field of substrate before spraying is shown inFig. 4. The temperature field of substrate is non-uniform.Fig.2 Temperature curve during spraying processThere中国煤化工-ture areas. The majortempeC and the differenceTemperature curves of the second cycle and the four-is70YH_CN M H Ghe mnimum. Due 1oteenth are shown in Fig. 3. The mean temperature of thethe non-uniform temperature distribution and the largesecond cyele is 150C and the furteenth is 162心. There quanity of heat input from the plasma jet, coaing damageOn-line temperature monitoring and process diagnosis of plasma sprayed coatings2390 C diference between the areas of coating damage andtheir nearby areas, as denoted by the rectangles in Fig. 6. .260240220200181601401200100200300400500600700Fig.4 Temperature field of substrate before sprayingData pointswill happen.Fig.6 Temperature curve of the line A1-A10 in Fig. sTemperature field when coating damage happens isshown in Fig. 5. According to the comparison of Fig. 4 and3 ConclusionsFig.5, the regions of coating damage are observed in the(1) A new temperature investigation approach ofhigher temperature area and the temperature transition areacoatings with IR pyrometer is presented. This approachfrom the higher to the lower. The temperature mainly cen-enlarges the detecting scope of the device and improves thetralizes between 110 C and 200 C and the maximum isflexibility of the temperature monitoring system.higher than 300 C.(2) Coating damage always happens in the highertemperature area of substrates or the temperature transitionarea from the higher to the lower. When the difference be-tween the peak and the mean of the relevant region is be-yond 30-50 C or even higher, coating damage will 0C-cur. This case can give operators the fore-notice of coatingdamage and the feasible objective for process control.References[1] Fauchais P. Understanding plasma spraying. Joumal of Phys-ics D: Applied Physics, 2004, 37(9): R86 - R108.[2] Fauchais P, Vardelle M. How to improve the reliability andreproducibility of plasma sprayed coatings. Thermal Spray2003: Advancing the Science and Applying the Technology ,Fig.5 Temperature field when coating damage happensOrlando, FL, May5-8, 2003: 1165 -1173.[3] Moreau C. Towards a better control of themal spray procss.Thermnal Spray: Meeting the Challenges of the 21st Century,When the coating damage happens, the temperatureNice, France, May 25 -29, 1998: 1681 - 1693.curve will present an abnormal fluctuation due to the accu-mulation of large heat. This case can be selected as a ref-[4] Fauchais P, Vardelle A, Dussoubs B. Quo Vadis themnal中国煤化工Techogy, 2001, 10 .erence for measurement instruments and also as an initia-tion point for coating damage. As shown in Fig. 6, the[5]YHC NMHGa. Onhe mesremen .temperatures curve has a sharp climb trend around the are-of substrate temperature during thermal spraying. Thermala of coating damages. There are more than 30 C, or evenSpray Conects: Explore its Surfacing Polential. Basel ,24CHINA WELDING Vol. 19 No. 3 September 2010Switzerland, May2-4, 2005: 679 -683.New Mllenniun, Singapore, May 28 - 30, 2001: 779 -6] Sauer J P, Sahoo P. HVOF process control using Almen and86.temperature measurement. Thermal Spray 2001: New Sur-[ 9] Brandt 0, Wandelt M. Thermal measurements of subetratefaces for a New Milnnium, Singapore, May 28 -30, 2001 :during spray processes. Thermal Spray : Practical Solutions791 -796. .for Engineering Problems, Cincinnati, OH, October 7-11,7] Bertrand Ph, Ignatiev M, Flamant G, et al. Pyrometry appli-1996: 799 - 802..cations in themal plasma processing. Vacuum, 1999, 56 [10] Lugscheider E, Ladru F, Fischer A, et al. Plasma sprayed(1): 71 -76.ceramic coatings for electrical purposes necessity of process[8] Friedrich C J, Gadow R, Kilinger A, et al. IR thermnograph-control. Proceedings of the 24th Annual Conference of theic imaging - a powerful tool for on-line process control ofEE Industrial Electronics Society, Aachen, Germany,thermal spraying. Thernal Spray 2001: New Surfaces for aAugust 31, 1998: 2284 -2289.中国煤化工MYHCNMHG

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