爆炸喷涂技术制备热障涂层的研究

采用爆炸喷涂技术在M38G合金上制备热障涂层，分析了涂层的结构，形貌，显微硬度，并对涂层的氧化性能进行了研究，结果表明，爆炸喷涂制备的热障涂层均匀，致密，高温氧化过程中，陶瓷层与粘结层界面处生成了连续的Al2O3膜，使TBCs具有良好的抗高温氧化性。     

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。     

涂层致密度对MCrAlY涂层氧化行为的影响

采用等离子弧喷涂工艺和超音速火焰喷涂工艺分别制备MCrAlY涂层,利用扫描电镜、X射线衍射仪等研究不同工艺条件下涂层的结构特征,并研究2种涂层在1050℃时的高温氧化行为。结果表明:超音速火焰喷涂工艺可以使MCrAlY涂层获得更高的致密度,在高温氧化过程中该涂层表面可以形成致密的Al2O3膜层,减少NiO,尖晶石类复杂氧化物的出现。同等离子弧喷涂工艺相比,超音速火焰喷涂工艺制备的MCrAlY涂层在高温氧化过程中表现出较小的增重速率和致密的氧化物结构,有利于热障涂层整体寿命的提升。     

钛合金表面等离子喷涂热障涂层性能的研究

用等离子喷涂法在钛合金（Ti6Al4V）表面制备NiCrAlY＋（ZrO2＋Y2O3）陶瓷热障涂层。用XRD、SEM检测了涂层的金相组织、结构及形貌。对喷涂前后的试样在600℃进行了高温氧化实验,给出了氧化动力学曲线。结果表明．钛合金经等离子喷涂处理后表面形成陶瓷热障涂层且与基体结合紧密,涂层的厚度约为210um。所形成的热障涂层显著地提高了钛合金的高温抗氧化性能．降低了氧化速率,致密的氧化膜对继续氧化有阻碍作用。     

HCPEB作用下镀铝CoCrAlY涂层的高温氧化行为

使用大气等离子喷涂在镍基高温合金表面制备CoCrAlY粘结层并蒸镀一定厚度的纳米铝膜,利用强流脉冲电子束辐照镀铝涂层表面. 采用高温氧化试验,观察并分析涂层的高温氧化行为. XRD结果表明,强流脉冲电子束辐照镀铝涂层表层快速氧化生成大量Al2O3;100 h氧化后,表层氧化物成分较为稳定,基本保持Al2O3较多. 尖晶石类氧化物较少的状态. 表面形貌分析结果表明,经过强流脉冲电子束辐照镀铝涂层在高温环境下能够保持表层的致密和完整,缺陷很少. 涂层表层含有大量均匀且较为致密的Al2O3能够有效抵御外界环境的进一步氧化,有较好的的抗高温氧化性能.     

空心阴极电弧镀NiCrAlY涂层的抗氧化性能

采用空心阴极电弧离子镀技术制备NiCrAlY涂层,研究涂层的高温抗氧化性能。结果表明涂层组织致密,与合金结合状态良好。电弧离子镀NiCrAlY涂层在1 100℃恒温氧化100h后增重只有2.22mg/cm2,在100次循环氧化后仍没有失重现象,其抗恒温氧化和抗循环氧化性能远优于成分相近的超音速火焰喷涂、爆炸喷涂和大气等离子喷涂的NiCrAlY涂层。电弧离子镀NiCrAlY涂层在恒温氧化和循环氧化过程中表面均形成了连续致密、粘附性的氧化铝保护膜。氧化膜没有翘起和剥落现象,涂层组织在氧化后仍然完整致密。热喷涂NiCrAlY涂层在上述氧化过程中则生成了保护性较差的Ni、Cr和Al混合氧化物,并发生了氧化膜剥落,同时有严重的内氧化现象。     

YAG/8YSZ双陶瓷热障涂层等温氧化性能研究

本文对比研究了YAG/8YSZ双陶瓷和8YSZ单陶瓷热障涂层体系的抗高温氧化性能。采用爆炸喷涂(D-GUN)在310S耐热不锈钢基体上制备粘结层(NiCoCrAlY),用大气等离子喷涂(APS)分别在粘结层试样上制备YAG/8YSZ双陶瓷和8YSZ单陶瓷热障涂层,利用SEM和XRD分析涂层氧化前后截面与表面特征,对比研究2种热障涂层体系在1100 ℃等温氧化不同时间后的氧化增重动力学、YAG陶瓷层微观结构与物相及TGO生长过程和生长动力学。结果表明,YAG陶瓷层在1100 ℃等温氧化200 h后无明显相结构转变,孔隙率稍有降低;YAG/8YSZ双陶瓷层体系较8YSZ单陶瓷层体系氧化增重速率降低1.7倍,TGO生长速率降低1.4倍,粘结层β-NiAl相消耗速度及岛状氧化物生长速度更低,表现出更好的抗高温氧化性能。     

等离子喷涂 NiCoCrAlY / Al2 O3 高温固体润滑耐磨涂层的抗氧化性能研究

目的研究等离子喷涂NiCoCrAlY/Al2O3高温固体润滑耐磨涂层在850℃时的高温抗氧化性能和抗氧化机理。方法采用喷雾造粒、化工冶金包覆技术制备NiCoCrAlY/Al2O3复合粉体,并采用等离子喷涂技术在45#钢表面制备NiCoCrAlY/Al2O3复合涂层。采用SEM和XRD研究粉体和涂层的显微结构和物相组成,并采用马弗炉研究复合涂层在850℃的恒温氧化动力学曲线,通过研究氧化96 h以后涂层表面的组织形貌,探讨NiCoCrAlY/Al2O3复合涂层的抗氧化机理。结果 NiCoCrAlY合金层均匀致密地包覆在Al2O3颗粒的表面,包覆层厚度约为3~5μm。复合粉体的主要组成为Al2O3相和NiCoCrAlY合金相,没有其他杂质相的存在。等离子喷涂NiCoCrAlY/Al2O3复合涂层氧化动力学曲线分为大斜率直线、抛物线和系数几乎为0的抛物线等3个阶段。氧化96 h以后,涂层的氧化质量增量为4.9 mg/cm2左右,表面形成了一层连续的氧化物保护膜,经EDX分析,氧化膜层主要由Al,O,Cr和Ni组成。结论等离子喷涂NiCoCrAlY/Al2O3复合涂层具有良好的高温抗氧化性能,涂层中Ni,Cr,Al的氧化以及硬质相Al2O3的加入是涂层抗氧化的主要原因。     

热障涂层双层黏结层的高温氧化行为

采用箱式电阻炉研究了具有梯度热膨胀系数的（孔隙层+氧化层）双层黏结层结构热障涂层的高温氧化行为。采用气罩等离子喷涂在Inconel 738合金基材上制备60μm厚的孔隙层,通过超音速火焰喷涂（HVOF）在孔隙层上制备120μm厚的氧化层。在1000℃下对黏结层进行不同时间的高温氧化试验。结果表明,黏结层由孔隙层和氧化层组成;喷涂态孔隙层具有典型的层状结构,未出现明显氧化;喷涂态氧化层较为致密,内部弥散分布着细小的α-Al₂O₃颗粒;具有梯度热膨胀系数黏结层表面的热生长氧化物（TGO）生长速率显著低于传统黏结层,且不再遵循抛物线生长规律,而是以对数规律生长;由于生长速率缓慢,尽管在制备过程中消耗了部分Al元素,但在500 h范围内TGO仍然以α-Al₂O₃为主。      

高能高速等离子喷涂MCrAlY涂层的抗高温氧化性能

为提高Ni3Al基高温合金IC6的抗高温氧化性能,采用高能高速等离子喷涂设备在其表面制备了MCrAlY涂层,测试了1 000℃高温条件下经300h氧化后涂层的抗氧化性能。结果表明:300h试验后,涂层的单位面积氧化增重为5.584g/m2,氧化速率为0.019g/m2·h,达到了完全抗氧化级。分析认为:高能高速等离子喷涂工艺制备的MCrAlY涂层与基体结合紧密,孔隙、裂纹及氧化物夹杂含量少,有效的阻隔了氧气的扩散通道,使得氧化物的生长缓慢。同时在高温氧化过程中,涂层表面生成了大量的Al2O3膜,阻碍了金属原子与氧原子的扩散,降低了涂层的氧化速率。另外涂层中含有的Y及Y2O3增加了氧化膜的粘附性,对氧元素的扩散具有抑制作用。     

CoNiCrAlY黏结层结构设计及其对热障涂层结合强度和抗热震性能的影响

目的 设计热障涂层黏结层结构,改善涂层结合强度和抗热震性能。方法 制备了5种结构的CoNiCrAlY黏结层,即超音速火焰喷涂(HVOF)底层+等离子喷涂(APS)上层的双层结构黏结层试样,对其进行1 050℃真空热处理3 h后的试样,APS黏结层试样,HVOF黏结层试样及其真空热处理试样。再在以上5种试样表面制备Y₂O₃部分稳定ZrO₂(YSZ)陶瓷层,研究黏结层的表面粗糙度、相组成、微观组织结构及其对涂层试样结合强度、热震性能的影响。结果 制备态的黏结层由γ/γ’和β-NiAl两相组成,真空热处理后β相含量增多,表面粗糙度下降。在所有涂层试样中,双黏结层的涂层试样的结合强度最低,为28.43 MPa;对其真空热处理后得到的涂层试样的结合强度最高,达到39.42 MPa,主要原因在于热处理促进了两黏结层之间的扩散,提高了界面强度。双黏结层的涂层试样的抗热震性能最好,200次热震后涂层无明显剥落,而APS黏结层的涂层试样的抗热震性能最差,涂层抗热震性能的差异在于黏结层微观结构的不同。结论 双黏结层的结构设计综合了APS、H...     

Thermal fatigue behavior of thermal barrier coatings with the MCrAlY bond coats by cold spraying and low-pressure plasma spraying

The thermal fatigue behavior of thermal barrier coatings (TBCs) with the NiCoCrAlTaY bond coats deposited by cold spraying and low-pressure plasma spraying (LPPS) was examined through thermal cyclic test. The TBCs were subjected to the pre-oxidation before the test in an Ar atmosphere. The results show that a more uniform TGO in both thickness and composition forms on the cold-sprayed bond coat than that deposited by LPPS. The TBCs with the cold-sprayed bond coat exhibit a longer thermal cyclic lifetime than that with the LPPS bond coat. The differences in oxidation behavior and thermal cyclic behavior between two TBCs were discussed based on the evident difference in the surface morphology of two MCrAlY bond coats deposited by cold spraying and LPPS.     

粘结层预处理对PS-PVD沉积7YSZ热障涂层氧化行为的影响

目的提高PS-PVD沉积7YSZ热障涂层的抗高温氧化性能。方法采用等离子喷涂-物理气相沉积(PS-PVD)分别在未预处理和预处理(抛光+预氧化)的粘结层表面制备了柱状结构7YSZ热障涂层,并在大气环境下测试了柱状结构7YSZ热障涂层的950℃静态高温氧化性能。利用扫描电子显微镜、X射线衍射仪、能谱仪对高温氧化过程中的陶瓷层/粘结层界面形貌、TGO层结构演变进行表征。结果粘结层的抛光处理能够降低表面几何受力不均匀部位,抑制陶瓷层/TGO/粘结层界面处微裂纹的产生,同时粘结层的预氧化处理形成的薄而连续的TGO层能有效降低TGO的生长速度,抑制陶瓷层-粘结层之间的元素互扩散。柱状结构7YSZ涂层的高温氧化动力学曲线符合Wagner抛物线规律,粘结层未预处理和预处理的7YSZ热障涂层的氧化速率常数分别为0.101×10~(-12) cm~2/s和0.115×10~(-13) cm~2/s。结论粘结层预处理能有效改善等离子物理气相沉积7YSZ热障涂层的抗氧化性能。     

High temperature properties of thermal barrier coatings obtained by detonation spraying

NiCrAlY/YPSZ and NiCrAlY/NiAl/YPSZ thermal barrier coatings (TBCs) were successfully deposited by detonation spraying. The results indicated that the detonation sprayed TBCs included a uniform ceramic coat containing a few microcracks and a bond coat with a rough surface. The lamellar structure and the presence of cracks and impurities could reduce the thermal conductivity of the ceramic coat. Oxidation kinetics at 1000–1150 °C of detonation sprayed TBCs have been measured and discussed. The role of a Ni–Al intermediate layer in improving the oxidation resistance of duplex TBCs has also been studied.     

Preparation and Bond Properties of Thermal Barrier Coatings on Mg Alloy with Sprayed Al or Diffused Mg-Al Intermetallic Interlayer

Sprayed Al or diffused Mg-Al layer was designed as interlayer between the thermal barrier coatings (TBCs) and Mg alloy substrate. The effects of the interlayer on the bond properties of the coats were investigated. Al layers were prepared by arc spraying and atmospheric plasma spraying (APS), respectively. Mg-Al diffused layer was obtained after the heat treatment of the sprayed sample (Mg alloy with APS Al coat) at 400 °C. The results show that sprayed Al interlayer does not improve the bond stability of TBCs. The failure of the TBCs on Mg alloy with Al interlayer occurs mainly due to the low strength of Al layer. Mg-Al diffused layer improves corrosion resistance of substrate and the bond interface. The TBCs on Mg alloy with Mg-Al diffused interlayer shows better bond stability than the sample of which the TBCs is directly sprayed on Mg alloy substrate by APS.     

Structure and durability evaluation of YSZ + Al2O3 composite TBCs with APS and HVOF bond coats under thermal cycling conditions

Plasma sprayed thermal barrier coatings (TBCs) are applied to gas turbine components for providing thermal insulation and oxidation resistance. The TBC systems currently in use on superalloy substates typically consists of a metallic MCrAlY based bond coat and an insulating Y₂O₃ partially stabilized ZrO₂ as a ceramic top coat (ZrO₂ 7–8 wt.% Y₂O₃). The oxidation of bond coat underlying yttria stabilized zirconia (YSZ) is a significant factor in controlling the failure of TBCs. The oxidation of bond coat induces to the formation of a thermally grown oxide (TGO) layer at the bond coat/YSZ interface. The thickening of the TGO layer increases the stresses and leads to the spallation of TBCs. If the TGO were composed of a continuous scale of Al₂O₃, it would act as a diffusion barrier to suppress the formation of other detrimental mixed oxides during the extended thermal exposure in service, thus helping to protect the substrate from further oxidation and improving the durability. The TBC layers are usually coated onto the superalloy substrate using the APS (Atmospheric plasma spray) process because of economic and practical considerations. As well as, HVOF (High velocity oxygen fuel) bond coat provides a good microstructure and better adhesion compared with the APS process. Therefore, there is a need to understand the cycling oxidation characteristic and failure mode in TBC systems having bond coat prepared using different processes. In the present investigation, the growth of TGO layers was studied to evaluate the cyclic oxidation behavior of YSZ/Al₂O₃ composite TBC systems with APS-NiCrAlY and HVOF-NiCrAlY bond coats. Interface morphology is significantly effective factor in occurrence of the oxide layer. Oxide layer thickening rate is slower in APS bond coated TBCs than HVOF bond coated systems under thermal cycle conditions at 1200 °C. The YSZ/Al₂O₃ particle composite systems with APS bond coat have a higher thermal cycle life time than with the HVOF bond coating.     

EB-PVD热障涂层热循环过程中粘结层的氧化和相结构

采用磁控溅射方法在镍基单晶高温合金基体上沉积Ni-30Cr-12Al-0.3Y（质量分数，％）粘结层，采用电子束物理气相沉积方法（EB－VPD）沉积7％Y2O3（质量分数）－ZrO2陶瓷顶层，结果表明，在热循环过程中，非平衡相t′-ZrO2中的Y2O3含量逐渐减少，t′－ZrO2相逐渐分解成平衡相t-ZrO2（冷却时变转变成斜相）和立方组ZrO2,1050℃循环200次，粘结层氧化物（Al2O3)厚度约为3μm，表明Ni-Cr-Al-Y达宜作粘结层，继续热循环，陶瓷层中出现单斜阳，粘结层中Al贫化，氧化层中出现NiO及尖晶石等，引起应力集中，导致涂层失效。     

Thermal Failure of Nanostructured Thermal Barrier Coatings with Cold-Sprayed Nanostructured NiCrAlY Bond Coat

Nanostructured thermal barrier coatings (TBCs) were deposited by plasma spraying using agglomerated nanostructured YSZ powder on Inconel 738 substrate with cold-sprayed nanostructured NiCrAlY powder as bond coat. The isothermal oxidation and thermal cycling tests were applied to examine failure modes of plasma-sprayed nanostructured TBCs. For comparison, the TBC consisting of conventional microstructure YSZ and conventional NiCrAlY bond coat was also deposited and subjected to the thermal shock test. The results showed that nanostructured YSZ coating contained two kinds of microstructures; nanosized zirconia particles embedded in the matrix and microcolumnar grain structures of zirconia similar to those of conventional YSZ. Although, after thermal cyclic test, a continuous, uniform thermally grown oxide (TGO) was formed, cracks were observed at the interface between TGO/BC or TGO/YSZ after thermal cyclic test. However, the failure of nanostructured and conventional TBCs mainly occurred through spalling of YSZ. Compared with conventional TBCs, nanostructured TBCs exhibited better thermal shock resistance.     

TGO growth behaviour in TBCs with APS and HVOF bond coats

The growth of thermally grown oxide (TGO) layers and their influence on crack formation were studied for two thermal barrier coating (TBC) systems with CoNiCrAlY bond coats produced by (i) air plasma spray (APS) and (ii) high-velocity oxy-fuel (HVOF) techniques. All samples received a vacuum heat treatment and were subsequently subjected to thermal cycling in air. The TGOs were predominantly comprised of layered alumina, along with some oxide clusters of chromia, spinel and nickel oxide. However, after extended oxidation, the alumina layer formed in the APS-CoNiCrAlY bond coat transformed to chromia/spinel, while that formed in the HVOF-CoNiCrAlY bond coat remained stable. TGO thickening in the APS-CoNiCrAlY bond coat generally exhibited a three-stage growth behavior, which resembles a high temperature creep curve, whereas growth of the alumina layer in the HVOF-CoNiCrAlY bond coat showed an extended steady-state stage. Crack propagation in these two TBCs was found to be related to the growth and coalescence of oxide-induced cracking, connecting with pre-existing discontinuities in the topcoat. Hence, crack propagation during thermal cycling appeared to be controlled by TGO growth.