等离子喷涂热障涂层高温风洞热震行为

采用等离子喷涂工艺制备ZrO2-8%Y2O3(质量分数,下同)陶瓷层,冷喷涂制备CoNiCrAlY粘结层,在高温燃气风洞条件下测试热障涂层的热震性能,并研究了高温氧化处理对试样热震性能的影响.结果表明,等离子喷涂热障涂层具有较好的抗热震性能,经过100次热震循环后,涂层与基体结合良好,涂层较为完整,未出现大面积的剥落;经过氧化处理后的试样抗热震性较差.     

AZ91D表面Ni-P/Al YSZ复合热障涂层的热震失效研究

目的研究带有Ni-P/Al复合中间层的AZ91D镁合金表面氧化钇稳定氧化锆热障涂层(YSZ TBCs),在400℃水淬热震实验中的失效行为。方法通过化学镀和等离子喷涂(APS)技术,在Mg合金表面制备带有Ni-P和Ni-P/Al中间层的NiCrAlY/YSZTBCs。于400℃水淬热震试验中进行涂层样品的失效行为及机理研究。利用X-射线衍射仪(XRD)、能谱仪(EDS)及扫描电镜(SEM)等,分析带有Ni-P、Ni-P/Al中间层的YSZ TBCs的物相组成和热震失效前后的显微组织。结果带有Ni-P中间层的YSZ TBCs在平均热冲击循环61次后,涂层表面积的60%发生剥落;带有Ni-P/Al复合中间层的YSZTBCs在平均热冲击循环91次后,整片涂层从基体上剥落分离。微观形貌结果表明,在水淬过程中,水介质进入异种金属界面处,化学性质活泼的Mg合金基体和金属Al均发生电偶腐蚀且前者更甚。在400℃加热-水淬过程中,NiCrAlY粘结层和Mg合金基体由于热膨胀系数不同,层间的热应力不断积累并作用于中间层。在腐蚀应力和热应力共同作用下,Ni-P层和Al层发生断裂,涂层剥离失效。结论 Ni-P/Al复合中间层能有效提高镁合金基体抗氧化能力和抗腐蚀能力,且涂层内热应力明显减小,整个涂层表现出更好的热稳定性,热震寿命有所提高。     

超音速等离子弧喷涂ZrO_2/CoNiCrAlY热障涂层界面高温氧化性能研究

采用超音速等离子弧喷涂设备在35Cr Mo钢基体上制备了Zr O_2/Co Ni Cr Al Y热障涂层,并将涂层加热到1 150℃进行氧化试验。利用扫描电子显微镜和X射线衍射方法对涂层的组织结构和相组成进行了分析,并对元素扩散情况进行研究。结果表明,涂层组织致密,界面结合良好,无剥落;粘结层表面存在少量尖角和钩状突出颗粒。热障涂层经过1 150℃加热后,在粘结层与陶瓷层的界面处出现少量深颜色的热生长氧化物(thermally grown oxide,简称TGO);随着氧化时间的延长,TGO层厚度明显增加并且开始连续。通过对Zr O_2-8Y2O3/Co Ni Cr Al Y界面扫描发现,该处Al元素出现了的富集峰,而Cr和Ni元素的含量远小于金属黏结层中含量,并且Cr和Ni元素的变化趋势为沿界面呈梯度下降,TGO层由亚稳态的θ-Al2O3逐渐转变为稳定态的α-Al2O3,有效地提高了涂层的抗高温氧化性能。     

NiCoCrAlY粘结层喷涂工艺对8YSZ热障涂层抗氧化性能的影响

目的 提高热障涂层粘结层的抗高温氧化性能。方法 分别采用爆炸喷涂和等离子喷涂工艺制备了不同结构的NiCoCrAlY粘结层,之后通过等离子喷涂制备8YSZ陶瓷层,分析了两种粘结层结构的热障涂层的抗高温氧化性能。利用XRD、SEM和EDS对涂层物相、微观结构和成分进行分析,并对其与基体结合状态、抗高温氧化性能进行研究。结果 爆炸喷涂粘结层内部组织致密,缺陷较少,与基体结合处孔隙少;而等离子喷涂粘结层内部的层状特征明显,孔隙较多,表面粗糙度较低。爆炸喷涂粘结层氧化5 h后,表面生成了一层富Al2O3的致密氧化物膜;而等离子喷涂粘结层表面形成了富NiO、CoO、Cr2O3和Ni(Cr,Al)2O4的氧化物层,并出现了许多微裂纹和片层状氧化物。爆炸喷涂制备的热障涂层试样在前5 h氧化增重速率高于等离子喷涂试样,随后变平缓,而等离子喷涂试样氧化速率依然较高。爆炸喷涂热障涂层的热生长氧化物层（Thermally grown oxide, TGO）经50 h氧化后,仍呈连续状,厚度均匀,粘结层内氧化物缺陷较少。结论 爆炸喷涂粘结层组织均匀、致密,喷涂时涂层的氧化以及热处理的内氧化较少,使得足够的Al较快速地在粘结层表面形成致密的氧化铝,表面一定厚度的氧化铝层抑制了氧和其他金属原子的相向扩散反应,提高了涂层的抗高温氧化性能。     

等离子喷涂纳米热障涂层热震性能

采用等离子喷涂工艺制备常规和纳米结构ZrO2-7%Y2O3热障涂层,比较两种涂层在850℃下的热震性能,并探讨其热震失效机理。结果表明,不管是首次出现宏观裂纹(局部剥落)还是达到热震失效,纳米结构热障涂层的热震次数都明显高于相应的常规涂层。相对于常规涂层,纳米结构涂层有较好的抗热震性能。等离子喷涂常规热障涂层的热震失效形式为大面积整体剥落,而纳米结构热障涂层热震失效形式为边角局部剥落。     

Al2O3对等离子喷涂热障涂层高温氧化及热震性能的影响

采用等离子喷涂 (PS)在GH5 36高温合金基材上制备了典型的双层热障涂层 (TBCs)和两种分别加入了Al2 O3 陶瓷成分的复合热障涂层。典型的TBCs采用Ni2 2Cr10AlY连接层与 8%Y2 O3 稳定的 (8YPSZ)顶层的双层结构 ;多层涂层分别采用Al2 O3 与Ni2 2Cr10AlY复合的连接层和Al2 O3 与 8YPSZ复合的顶层。3种类型试样的10 0h ,10 0 0℃静态氧化及 10 5 0℃热震试验的结果分析表明 :8YPSZ Al2 O3 的复合氧障层具有最佳的氧化阻力 ;Ni2 2Cr10AlY 8YPSZ双层涂层的热震阻力最佳 ,氧化阻力最差 ;连接层采用Ni2 2Cr10AlY Al2 O3 复合涂层具有热震和静态氧化条件下综合优良的高温热循环性能     

等离子喷涂梯度热障涂层的抗热震性能

对比研究了等离子喷涂梯度热障涂层与双层热障涂层,试验中梯度热障涂层选用不同比例的Ni Co Cr Al Y与Zr O2-8%Y2O3复合粉末作为梯度过渡层材料,并对两种结构的热障涂层进行了抗热震性能试验。结果表明,梯度热障涂层的抗热震寿命明显高于双层热障涂层的抗热震寿命。     

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。     

耐热钢表面等离子喷涂NiCrAlY＋(ZrO2＋Y2O3)热障涂层性能研究

利用等离子喷涂法在耐热钢1Cr18Ni9Ti基体表面喷涂NiCrAlY＋（ZrO2＋Y2O3）陶瓷热障涂层，并进行高温隔热性能试验，用XRD、SEM检测了试样的金相组织、结构及形貌，结果表明，陶瓷热障涂层与1Cr18Ni9Ti基体结合紧密；表面陶瓷层经高温氧化后处理后其硬度显著增高；进行850℃高温隔热性能试验，1Cr18Ni9Ti表面热障涂层隔热能力显著提高，达75℃。     

阴极等离子电解大面积沉积弥散Pt微粒增韧8YSZ热障涂层

采用大气等离子喷涂(APS)在高温合金表面制备一层Ni Co Cr Al Y粘结层,然后采用阴极等离子电解沉积(CPED)制备一层弥散Pt微粒的8YSZ涂层。通过在电解液中加入陶瓷微珠,促使阴极表面发生均匀的等离子微弧放电,实现了在大面积样品上沉积8YSZ涂层。获得的涂层厚度到达120μm,具有多孔结构,由立方相和四方相8YSZ以及Pt组成。1100℃空气中循环氧化的结果表明,随着涂层中Pt含量的的增加,涂层的抗高温氧化和抗剥落性能得到明显提高。Pt微粒对8YSZ涂层的增韧作用主要为:Pt微粒塑性变形吸收裂纹扩展的能量,钝化裂纹尖端,减小裂纹尺寸,提高涂层的临界断裂应力。     

NiAl/NiCoCrAlY/8YSZ复合喷涂层的微观结构与性能研究

目的提高金属/陶瓷隔热涂层体系在海洋环境下的耐腐蚀性能。方法利用冷喷涂方法制备NiAl复合打底层和Ni CoCrAlY粘结层,与等离子喷涂制备的8YSZ陶瓷层构成适用于海洋环境的多层结构耐蚀隔热涂层体系。利用FE-SEM分别观察喷涂态粘结层和陶瓷层的表面、横截面形貌,通过EDS分析涂层元素分布;利用XRD分析表征涂层的物相组成;借助万能材料试验机,采用拉伸法测试涂层结合强度;利用热循环试验和焰流冲刷试验测试涂层的耐高温性能。结果微观分析表明,冷喷涂制备的NiAl复合打底层和Ni CoCrAlY粘结层形貌致密,涂层材料未发生明显氧化,颗粒变形程度不一,粘结层与基体间的结合强度约为18.4 MPa,粘结层与8YSZ陶瓷层界面结合紧密。陶瓷层物相结构和成分稳定,涂层经12次热震循环和1000个周期的高温焰流冲击后,表面未出现开裂、起皮和脱落。结论采用冷喷涂法和等离子喷涂法联合制备的耐蚀隔热复合涂层体系具备良好的耐热性和耐腐蚀性。冷喷涂制备的金属涂层结构致密,孔隙率低,与陶瓷层结合良好,能够有效提高涂层体系在腐蚀性环境中的耐蚀性能。NiAl复合涂层可以缓解Ni CoCrAlY粘结层和铝合金基材间的热匹配问题,增强涂层的结合性能。     

等离子喷涂La2(Zr0.7Ce0.3)2O7热障涂层的抗热震性能

采用等离子喷涂制备了La₂(Zr_0.7Ce_0.3)₂O₇（LZ7C3）热障涂层,并对涂层的微观组织、相结构、成分、相稳定性、涂层热导率以及抗热震性能进行了研究.结果表明,LZ7C3涂层由单相烧绿石结构物质组成,高温稳定性较好;涂层的热导率较块材下降约20%,这是由于涂层具有较高的孔隙率所致:涂层在不同温度范围的热震寿命和失效机制不同,在室温至约1000℃间的热震寿命为116 cyc,涂层失效方式以片状剥落为主:在室温至1100℃间的热震寿命为53 cyc,涂层失效方式为片状剥落和层状撕裂;在室温至1200℃间的热震寿命为3 cyc,涂层失效方式以层状撕裂为主.     

Study of microstructure and thermal shock behavior of two types of thermal barrier coatings

Gas turbines provide one of the most severe environments challenging material systems nowadays. Only an appropriate coating system can supply protection particularly for turbine blades. This study was made by comparison of properties of two different types of thermal barrier coatings (TBCs) in order to improve the surface characteristics of high temperature components. These TBCs consisted of a duplex TBC and a five layered functionally graded TBC. In duplex TBCs, 0.35 mm thick yittria partially stabilized zirconia top coat (YSZ) was deposited by air plasma spraying and ～0.15 mm thick NiCrAlY bond coat was deposited by high velocity oxyfuel spraying. ～0.5 mm thick functionally graded TBC was sprayed by varying the feeding ratio of YSZ/NiCrAlY powders. Both coatings were deposited on IN 738LC alloy as a substrate. Microstructural characterization was performed by SEM and optical microscopy whereas phase analysis and chemical composition changes of the coatings and oxides formed during the tests were studied by XRD and EDX. The performance of the coatings fabricated with the optimum processing conditions was evaluated as a function of intense thermal cycling test at 1100 °C. During thermal shock test, FGM coating failed after 150 and duplex coating failed after 85 cycles. The adhesion strength of the coatings to the substrate was also measured. Finally, it is found that FGM coating has a larger lifetime than the duplex TBC, especially with regard to the adhesion strength of the coatings.     

Improvement of thermal shock resistance for thermal barrier coating on aluminum alloy with various electroless interlayers

NiCoCrAlY/8YSZ coating was firstly directly deposited on aluminum alloy 5A06 by atmospheric plasma spray to make it applicable to short-time high temperature condition. The failure after thermal shock test was mainly due to the stress caused by thermal expansion mismatch between the bond coat and the substrate as well as the galvanic corrosion of the aluminum alloy. Ni-P, Ni-W-P and Ni-Cu-P as interlayers were electrolessly deposited on the substrate in order to mitigate the thermal stress. The composition and thermal transformation of the interlayers were investigated. Thermal shock resistance and bonding strength of multilayer coatings (interlayer/NiCoCrAlY/8YSZ) were tested. Diffusion layers mainly composed of AlNi, Al₃Ni₂ and Al₃Ni were observed between the interlayers and the substrate after thermal shock test. The oxidation of the substrate was effectively inhibited. Ni-P interlayer obtained at lower pH value was superior to the other two interlayers and enhanced the thermal shock life from 38 to more than 200 cycles. With the application of the Ni-P and Ni-Cu-P interlayers, the bonding strength examined by pull-off test was also largely improved from 11.7 MPa to 18.8 and 19.0 MPa, respectively.     

Plasma spraying of functionally graded yttria stabilized zirconia/NiCoCrAlY coating system using composite powders

Pre-alloyed and plasma spheroidized composite powders were used as the feedstock in the plasma spraying of functionally graded yttria stabilized zirconia (YSZ)/NiCoCrAlY coatings. The ball milling parameters of the composite powders and the plasma spraying parameters for preparing functionally graded materials (FMGs) coatings were optimized to obtain the best performance for the thermal barrier coatings (TBCs). Microstructure, physical, mechanical, and thermal properties of YSZ/NiCoCrAlY FGMs coatings were investigated and compared with those of traditional duplex coatings. Results showed that the advantages of using pre-alloyed composite powders in plasma spraying were to ensure chemical homogeneity and promote uniform density along the graded layers. Microstructure observation showed the gradient distribution of YSZ and NiCoCrAlY phases in the coating, and no clear interface was found between two adjacent different layers. Oxidation occurred during plasma spray and the resultant aluminum oxide combines with YSZ in a wide range of proportions. The bond strength of functionally graded coatings was about twice as high as that of the duplex coatings because of the significant reduction of the residual stresses in the coatings. The thermal cycling resistance of functionally graded coating was much better than that of duplex coating.     

20%NiCr-80%Cr3C2涂层抗热冲击和抗氧化性能研究

目的针对工作温度较低(低于550℃)的热作模具,研究热喷涂20%NiCr-80%Cr3C2涂层在5CrNiMo热作模具钢基体上的抗热冲击和抗氧化性能。方法利用超音速火焰喷涂技术(HVOF)在5CrNiMo热作模具钢基体上制备20%NiCr-80%Cr3C2涂层。采用维氏显微硬度计和万能力学试验机分别测试涂层表面的显微硬度和结合强度;采用管式炉研究涂层在250~550℃之间的抗循环热冲击及抗氧化性能;采用光学显微镜、扫描电子显微镜、能谱仪和X射线衍射仪分析表征涂层经循环热冲击试验前后样品的形貌、组织结构及物相组成。结果20%NiCr-80%Cr3C2涂层组织均匀致密,具有极高的表面显微硬度(818.9HV)和结合强度(64.0MPa)。200次循环热冲击后,涂层内部产生了微裂纹,但并未相互连通,样品表面依旧保持光洁平整,且粘接相中析出的碳化物颗粒使涂层硬度大幅提高(1029.0HV)。涂层与基体界面形成了Fe和Cr元素的氧化物层,但其厚度增至约1μm后处于稳定阶段,且该氧化层连续致密,与基体和涂层结合良好,并未表现出使涂层剥离的倾向。结论利用HVOF制备的20%NiCr-80%Cr3C2涂层抗循环热冲击性能良好,且能够有效提高5CrNiMo热作模具钢工作表面的硬度和抗氧化性能。     

Comparison of thermal shock behaviors between plasma-sprayed nanostructured and conventional zirconia thermal barrier coatings

NiCoCrAlTaY bond coat was deposited on pure nickel substrate by low pressure plasma spraying(LPPS), and ZrO2-8%Y2O3 (mass fraction) nanostructured and ZrO2-7%Y2O3 (mass fraction) conventional thermal barrier coatings(TBCs) were deposited by air plasma spraying(APS). The thermal shock behaviors of the nanostructured and conventional TBCs were investigated by quenching the coating samples in cold water from 1 150, 1 200 and 1 250 ℃, respectively. Scanning electron microscopy(SEM) was used to examine the microstructures of the samples after thermal shock testing. Energy dispersive analysis of X-ray(EDAX) was used to analyze the interface diffusion behavior of the bond coat elements. X-ray diffractometry(XRD) was used to analyze the constituent phases of the samples. Experimental results indicate that the nanostructured TBC is superior to the conventional TBC in thermal shock performance. Both the nanostructured and conventional TBCs fail along the bond coat/substrate interface. The constituent phase of the as-sprayed conventional TBC is diffusionless-transformed tetragonal(t′). However, the constituent phase of the as-sprayed nanostructured TBC is cubic(c). There is a difference in the crystal size at the spalled surfaces of the nanostructured and conventional TBCs. The constituent phases of the spalled surfaces are mainly composed of Ni2.88Cr1.12 and oxides of bond coat elements.