搭接率对激光重熔氧化锆涂层结构及热震性能的影响
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摘要
针对大面积激光重熔热障涂层后搭接区域结构的变化影响涂层使用寿命这一问题,对氧化锆涂层进行多道次激光重熔,探究了不同搭接率下重熔涂层表面及截面微观组织形貌的变化规律,并在电阻式加热炉中进行了热震实验,温度设定为1 050℃,分析随搭接率变化的涂层结构对热循环寿命的影响规律。通过扫描电镜观察发现:前后两个道次重熔层的裂纹在分界线处相互贯通,随着搭接率的增加,搭接区域的裂纹密度随之减小,而凹坑和微块的数目随之增加;热震实验后,裂纹平均宽度减小至5μm,表面出现大量凹坑,大部分由微块脱落所致;随着搭接率的增加,搭接区域截面纵向裂纹的偏转角先增加后减小,而涂层的热循环寿命先减小后增加;截面纵向裂纹的偏转加速水平裂纹的产生,当搭接率为0.30时,偏转角最小;当涂层脱落面积达到20%及以上、搭接率为0.30时,重熔涂层的热循环寿命最长。
The life of thermal barrier coatings prepared by large-area laser remelting is affected by change of structure in overlap region.The yttria stabilized zirconia coating was subjected to multi-pass laser remelting,and the change law of the surface and the cross-section microstructure morphology of the remelted coating under different overlap rates were investigated.Thermal shock experiment was conducted at 1 050℃ in the resistance heating furnace to analyze the influence of the coating structure with change of the overlap rate on the thermal cycle life.The result observed by scanning electron microscope shows that cracks around the dividing line between adjacent laser remelted coatings cross each other.In overlap region,with the increasing overlap rate,the density of cracks decreases,while the pits and small crumblings increase.After thermal shock experiment,the average width of surface crack decreases to 5μm,and a largenumber of pits mostly caused by exfoliation of small fragments appear on the surface of laser remelted coating.As the overlap ratio increases,the deflection angle of the longitudinal cracks in the overlap region increases first and then decreases,while the thermal cycle life of the coating first decreases and then increases.The deflection of section longitudinal cracks in overlap region accelerates the generation of horizontal cracks,and the deflection angle is smallest when the overlap rate is 0.30.When the exfoliation percentage is or more than 20%,the laser remelted coating with 0.30 of overlap rate performs best.
The life of thermal barrier coatings prepared by large-area laser remelting is affected by change of structure in overlap region.The yttria stabilized zirconia coating was subjected to multi-pass laser remelting,and the change law of the surface and the cross-section microstructure morphology of the remelted coating under different overlap rates were investigated.Thermal shock experiment was conducted at 1 050℃ in the resistance heating furnace to analyze the influence of the coating structure with change of the overlap rate on the thermal cycle life.The result observed by scanning electron microscope shows that cracks around the dividing line between adjacent laser remelted coatings cross each other.In overlap region,with the increasing overlap rate,the density of cracks decreases,while the pits and small crumblings increase.After thermal shock experiment,the average width of surface crack decreases to 5μm,and a largenumber of pits mostly caused by exfoliation of small fragments appear on the surface of laser remelted coating.As the overlap ratio increases,the deflection angle of the longitudinal cracks in the overlap region increases first and then decreases,while the thermal cycle life of the coating first decreases and then increases.The deflection of section longitudinal cracks in overlap region accelerates the generation of horizontal cracks,and the deflection angle is smallest when the overlap rate is 0.30.When the exfoliation percentage is or more than 20%,the laser remelted coating with 0.30 of overlap rate performs best.
引文
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[18]LI Meiheng,SUN Xiaofeng.Thermal shock behavior of EB-PVD thermal barrier coating[J].Surface&Coating Technology,2007,201:7387-7391.
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[3]何利民.高温防护涂层[M].北京:国防工业出版社,2012:37-39.
[4]ZHU C,LI P,JAVED A.An investigation on the microstructure and oxidation behavior of laser remelted air plasma sprayed thermal barrier coatings[J].Surface&Coating Technology,2012,206:3739-3746.
[5]WANG Dongsheng,TIAN Zongjun,SHEN Lida,et al.Influences of laser remelting on microstructure of nanostructured Al2O3-13wt%TiO2coatings fabricated by plasma spraying[J].Applied Surface Science,2009,255:4606-4610.
[6]YANG L J,TANG J,WANG M L,et al.Surface characteristic of stainless steel sheet after pulsed laser forming[J].Applied Surface Science,2010,256:7018-7026.
[7]YANG L J,WANG Y,TIAN Z G,et al.YAG laser cutting soda-lime glass with controlled fracture and volumetric heat absorption[J].International Journal of Machine Tools and Manufacture,2010,50:849-859.
[8]FAN Zhengjie,WANG Kedian,DONG Xia,et al.Influence of columnar grain microstructure on thermal shock resistance of laser remelted ZrO2-7wt%Y2O3coatings and their failure mechanism[J].Surface Coatings Technology,2010,277:188-196.
[9]GHASEMI R,SHOJA-RAZAVI R,MOZAFARINIAR,et al.Laser glazing of plasma-sprayed nanostructured yttria stabilized zirconia thermal barrier coatings[J].Ceramics International,2013,39(8):9483-9490.
[10]MUSTAFA G G,GULTEKIN G.Microstructural evaluation of laser remelted gadolinium zirconate thermal barrier coating[J].Surface&Coating Technology,2015,276:202-209.
[11]MORKS M F,BERNDT C C,DURANDET Y,et al.Microscopic observation of laser glazed yttria stabilized zirconia coating[J].Applied Surface Science,2010,256:6213-6218.
[12]GHASEMIN R,RAZAVI S,MOZAFARINIA R,et al.The influence of laser treatment on thermal shock resistance of plasma sprayed nanostructured yttria stabilized zirconia thermal barrier coatings[J].Ceramics International,2014,40:347-355.
[13]孟庆瑞.激光重熔对等离子喷涂氧化锆热障涂层组织和性能的影响[D].济南:山东大学,2016:34-37.
[14]PARK J H,KIM J S,LEE K H,et al.Effects of the laser treatment and thermal oxidation behavior of CoN-iCrAlY/ZrO2-8Wt%Y2O3thermal barrier coating[J].Journal of Materials Processing Technology,2008,201(1/2/3):331-335.
[15]YANG L J,HOU C J,CHEN W Q,et al.Study on laser cutting carbon fibre reinforced composites[J].Materials Science Forum,2014,800:832-837.
[16]LEE J H,TSAI P C,CHANG C L,et al.Microstructure and thermal cyclic performance of laser glazed plasma sprayed CYSZ thermal barrier coating[J].Surface&Coating Technology,2008,202:5607-5612.
[17]冯浩源,孙登月,陈鹏,等.H13钢表面ZrO2-8%Y2O3涂层多道搭接激光重熔温度场数值模拟[J].焊接技术,2016,45(10):6-9.FENG Haoyuan,SUN Dengyue,CHEN Peng,et al.Numerical simulation of temperature field of laser remelting ZrO2-8%Y2O3coating on H13die steel surface[J].Welding Technology,2016,45(10):6-9.
[18]LI Meiheng,SUN Xiaofeng.Thermal shock behavior of EB-PVD thermal barrier coating[J].Surface&Coating Technology,2007,201:7387-7391.