Thermal Cycling Failure Research Articles

Novel high-entropy (La0.35Gd0.35Y0.35Sm0.35Yb0.6)Zr2O7 thermal barrier coatings: Thermal cycling performance and failure behavior

Novel high-entropy (La0.35Gd0.35Y0.35Sm0.35Yb0.6)Zr2O7 thermal barrier coatings: Thermal cycling performance and failure behavior

Investigating the CMAS corrosion resistance and thermal cycling failure behavior of porous thermal barrier coatings with different morphologies prepared by plasma spraying

Investigating the CMAS corrosion resistance and thermal cycling failure behavior of porous thermal barrier coatings with different morphologies prepared by plasma spraying

COP: A Combinational Optimization Power Budgeting Method for Manycore Systems in Dark Silicon

Dark silicon is a phenomenon of under-utilization in today's manycore systems due to power and thermal limitations. In order to improve the performance of dark silicon systems, it is necessary to adopt dynamic power constraints for different core mapping decisions. However, existing power budgeting methods are generally over pessimistic, e.g. Thermal Safe Power (TSP), or over optimistic, e.g. Greedy based Dynamic Power (GDP). This paper proposes a practical power budgeting method, called Combinational Optimization Power (COP). Different from existing methods, which ignore some actual factors, such as communication overhead and lifetime reliability, COP formulates the power budgeting problem as a thermal-constrained combinational optimization power problem. For the steady-state case, COP achieves the target fusion of optimized temperature and communication energy consumption by applying task priority ranking and task-to-core mapping. For the transient case, COP uses the rainflow counting algorithm to construct the reliability framework based on the thermal cycling failure mechanism, and then establishes a linear time-invariant transient temperature model to obtain the core mapping selection and the corresponding dynamic power budget. Experimental results demonstrate that COP is capable of providing an optimized core mapping decision, which can maximize power budget while ensuring the system performance.

Effect of temperature and thermal cycles on the mechanical behavior of sandwich structure with entangled metallic wire mesh

Effect of temperature and thermal cycles on the mechanical behavior of sandwich structure with entangled metallic wire mesh

Thermal cycling behavior and failure mechanism of Yb2O3-doped yttria-stabilized zirconia thermal barrier coatings

Thermal cycling behavior and failure mechanism of Yb2O3-doped yttria-stabilized zirconia thermal barrier coatings

Fabrication of ceramic sealing coatings for shell bionic structures and their failure mechanism during thermal cycling

The porous ceramic coating as a "brick" layer sprayed by air plasma spraying(APS) and MK resin as a "mud" layer prepared by a high viscosity spray gun were characterized and tested. Three specifications of the "brick-mud" layered ceramic sealing coating were fabricated through the cyclic and orderly deposition of the "brick" layer and "mud" layer, and the thermal cycling performance and failure mechanism of the three new coatings were studied. The results showed that the agglomerated Y 2 O 3 partially stabilized ZrO 2 (YSZ) particles had porous spherical structures and good sprayability, and the content of the YSZ phase in the prepared "brick" layer was 54.2%. The "mud" layer had good phase stability and was amorphous SiO 2 at and below 1100 °C. The fracture toughness of the pure YSZ coating was 2.295 ± 0.135 MPa‧m 0.5 , and which of the “mud” layer was reduced by 72.3%. The thermal cycling life of the conventional coating was only 67.3 times, which of A1, A2 and A3 coatings with 2, 3 and 6 "mud" layers were increased by 32.4%, 124.8% and 88.3%, respectively. In the thermal cycling process, the "weak" layer in the "brick-mud" layered coating led to the redistribution of internal stress and reduced the stress concentration in the top coating (TC)/TGO interface. Moreover, the initiation of microcracks in the "weak" layer, along with the "crack branching" effect and the "crack deflection" effect during the crack propagation process, could consume partial internal stress. Thus, the crack growth rates in the TC coating/TGO interface of the A1, A2 and A3coatings were lower than that of the conventional coating due to the above stress release mechanisms. In addition, the thermal cycling lives of the three new coatings with 2, 3 and 6 "mud" layers were improved to different degrees because of different stress effects. • A new ceramic sealing coating for a shell bionic structure has been fabricated. • The thermal cycling failure mechanism of the "brick-mud" layered coating has been elucidated. • The relationship between the number of layers and thermal cycling performance has been established.

Thermal cycling behavior and failure mechanism of the Si-HfO2 environmental barrier coating bond coats prepared by atmospheric plasma spraying

In this study, HfO 2 -doped Si bond coats with four different compositions were fabricated on the SiC substrates by atmospheric plasma spray (APS) for environmental barrier coating bond coats. The result showed that relatively dense composite bond coats can be successfully deposited by the APS approach using reduced plasma power to avoid the formation of metastable hafnia phases and hafnium silicides. The thermal expansion behavior of the Si-HfO 2 bond coat was investigated. Results indicated that plasma-sprayed Si-HfO 2 bond coats showed a non-linear expansion in air environment due to the oxidation of Si and formation of HfSiO 4 . Thermal cycling behavior of the Si-HfO 2 bond coat at 1300 ℃ was also studied. The result suggested that the Si-HfO 2 bond coat with high Si concentration has relatively better thermal shock resistance, owing to its low CTE and better oxidation resistance. The HfSiO 4 formation reaction between hafnia and silica alleviate the volume contraction caused by cristobalite phase transformation. The spallation of the bond coat was attributed to the formation of thermally grown oxides (TGO) and the coefficient of thermal expansion (CTE) mismatch between the bond coat and the SiC substrate. • Four different Si-HfO 2 bond coat with different Si content were deposited on SiC substrate by APS. • Optimum mixture composition found between 20 wt% and 40 wt% Si. • The Si-HfO 2 bond coat with high HfO 2 content accelerate the oxidation of Si. • The HfSiO 4 formation reaction restrain the cristobalite phase transformation.

Thermal Cycling Behavior and Failure Mechanism of the Si-Hfo2 Environmental Barrier Coating Bond Coats Prepared by Atmospheric Plasma Spraying

Thermal Cycling Behavior and Failure Mechanism of the Si-Hfo2 Environmental Barrier Coating Bond Coats Prepared by Atmospheric Plasma Spraying

Thermal Cycling Failure of Yb-Gd Co-Doped Srzro3 Coating Prepared by Solution Precursor Plasma Spray

Thermal Cycling Failure of Yb-Gd Co-Doped Srzro3 Coating Prepared by Solution Precursor Plasma Spray

Effect of SiC whiskers on thermal cycling performance of YSZ-Based sealing coating

Two types of Y2O3 partially stabilized ZrO2(YSZ)-based agglomerated powders with and without SiC whiskers were prepared by spray granulation, and the flow ability, apparent density and particle size distribution of them were investigated. The thermal cycling performance and failure mechanism of conventional high temperature sealing coating and modified one with additional layer with whiskers, which were sprayed by air plasma spraying (APS), were comparatively analyzed. The results showed that, compared to the powder without whiskers, the flow ability of that with whiskers reduced by 2.32%, and the apparent density and the proportion of 45–150 μm agglomerated powder increased by 1.53% and 2.29%, respectively. The thermal cycling failure mode of conventional high temperature sealing coating was the overall spalling of ceramic coating, and the spalling position originated from the interface of thermally grown oxide (TGO)/ceramic coating. Microstructure observation indicated that the structure integrity of SiC whiskers in the additional layer sprayed by APS was still retained. The whiskers were uniformly distributed and theinterface between bonding coating and ceramic coating exhibited excellent bonding. With the additional layer containing whiskers, the thermal cycling life of the coating was increased by 102.53%. In the thermal cycling process, the “bridging” and “pulling-out” effects of whiskers located at the additional layer consumed considerable energy, which could reduce the driving force of crack growth. Besides, a porous structure of the additional layer after thermal cycling was formed due to “bridging” and “pulling-out” of whiskers, further improving the thermal cycling life of coating with the additional layer.

Development of Silicon Carbide Interlayers for Plasma Spray Yttria Topcoat on Graphite for High-Temperature Applications

Abstract Plasma-sprayed yttria (Y2O3) coatings on commercial high-density graphite (HDG) as a chemical barrier coating are presently being explored for uranium-zirconium alloy melting crucibles in pyrochemical reprocessing of spent metallic fuel of future fast breeder reactors. The performance and durability of Y2O3 coatings for high-temperature exposure up to 1,823 K for multiple batch operations are critical to reducing solid active waste generation. However, plasma-sprayed Y2O3 coatings on HDG experience large thermal mismatch stresses due to the difference in the coefficient of thermal expansion (CTE) value of ∼8 × 10−6 K−1 for Y2O3 and ∼4 × 10−6 K−1 for HDG, combined with partial active oxidation of HDG interface leading to premature cracking and spallation of the coating. Silicon carbide (SiC) coating with intermediate CTE (∼6 × 10−6 K−1) offers superior oxidation protection for HDG, which can suitably be used as an interlayer to improve the durability of Y2O3 coatings. In the present work, SiC interlayer coating is developed on HDG substrates using conventional coating techniques such as pack cementation and chemical vapor deposition techniques for subsequent deposition of Y2O3 topcoat by plasma spraying. The thermal fatigue studies simulating uranium melting condition by isothermal hold at 1,723, 1,773, and 1,823 K for 1 h showed twofold improvements in the life of Y2O3 coatings with SiC interlayer. The evolution of thermal cycling damage and failure mechanisms are discussed. The role of interfacial microstructure, the stability of phases, and the underlying mechanisms for life enhancement in the presence of SiC interlayer for plasma-sprayed Y2O3 coating for high-temperature applications are highlighted.

The effect of vacuum heat treatment on microstructure, Al diffusion and thermal cycling lifetime of yttria stabilized zirconia by EB-PVD

• A TBCs system with NiCrAlYSi and YSZ was prepared by AIP-PVD and EB-PVD. • Diffusion has occurred on the interface due to the VHT at different temperatures. • The high thermal cycling lifetime relates to the relativity low TGO growth rate. Thermal barrier coatings (TBCs) with NiCrAlYSi bond coating and yttria stabilized zirconia ceramic coating were prepared by arc ion-plating PVD and electron beam-physical vapor deposition. The NiCrAlYSi BC was investigated by different vacuum heat treatment (VHT). Composition, phase and microstructure were studied by different characterization methods included scanning electron microscope and X-ray diffraction. With the temperature of VHT increasing, the growth and evolution of pores occurred on the interface between bond coating and substrate. The Al diffused from bond coating to substrate which played an important role in the high thermal performance of TBCs. The thermal cycling behavior and failure mechanism of Y 2 O 3 -stabilized ZrO 2 TBCs were evaluated and discussed in detail. The controlling of the diffusion rate of Al within NiCrAlYSi layer and the relatively low growth rate of thermally grown oxide appear to be relevant with the failure mechanism and high thermal performance.

LaGdZrO/YSZ thermal barrier coatings by EB-PVD: Microstructure, thermal properties and failure mechanism

Abstract Advanced thermal barrier coatings (TBCs) have got an increasing number of attention in advanced aero-engine. The thermal cycling life and failure behavior still remain a big challenge under high temperature. This work focuses on the microstructure, element diffusion, and cracks evolution of the LaGdZrO/YSZ (LGZ/YSZ) double ceramic layers (DCL) TBCs. Characterizations mainly include X-ray diffraction (XRD), scanning electron microscope (SEM), energy dispersive spectroscopy (EDS), transmission electron microscopy (TEM) and electron probe micro-analyzer (EPMA). The LGZ/YSZ DCL TBCs exhibit good thermal shock life and thermal cycling life. Element diffusion is investigated in detail, which is relevant with crack formation and propagation. After thermal cycling test, the failure regions mainly occur on the cracks regions and the interface regions. The interface instability plays a critical role on the failure behavior of LGZ/YSZ DCL TBCs.

Thermal cycling damage in pre-oxidized plasma-sprayed MCrAlY + YSZ thermal barrier coatings: Phenomenon of multiple parallel delamination of the TGO layer

This paper focuses on thermal cycling failure of pre-oxidized plasma-sprayed thermal barrier coatings (TBCs) with NiCrAlY and NiCoCrAlY bond-coats and yttria-stabilized zirconia (YSZ) top-coats. Pre-oxidation of full NiCrAlY + YSZ and NiCoCrAlY + YSZ TBC systems to the thickness of the thermally grown oxide (TGO) of ~3 μm was carried out mainly to reduce the influence of initial residual stresses related to the plasma spraying process. The NiCoCrAlY coatings were found to be rougher than the NiCrAlY coatings, the arithmetic average roughness Sa being nearly two times higher and the relative surface area RS being, respectively, ~1.8 and ~1.5 for the as-sprayed coatings. It was interesting to observe that despite much greater roughness of its bond-coat, the thermal cycling life of NiCoCrAlY + YSZ TBC system was more than a factor of two shorter when cycled at 1050 °C and still only comparable when cycled at 1150 °C. This resulted from much larger portion of the interface being influenced by repeated delamination of the TGO layer from the bond-coat, which formed multiple parallel alumina fragments of similar thickness. Most likely, the major cause for such behaviour was the higher thermal expansion of the NiCoCrAlY bond-coat and its higher oxidation rate, although the effect of the interfacial geometry certainly cannot be excluded.

Thermal cycling failure of the multilayer thermal barrier coatings based on LaMgAl11O19/YSZ

Abstract Thermal cycling failure of three multilayer TBCs based on LaMgAl11O19 (LaMA)/YSZ was comparatively investigated by using the burner-rig testing method in this work. Results indicate that through optimizing the weight ratio and thickness of the intermediate LaMA/YSZ composite layers, a five-layer TBC with much improved thermal cycling life of 11,749 cycles at 1372 °C surface and 1042 °C bond coat testing temperature has been realized. While, thermal cycling lifetimes of the tri- and six-layer TBCs were 7439 and 7804 cycles at surface/bond coat testing temperatures of 1378 °C/1065 °C and 1367 °C/1056 °C, respectively. Factors related to the 60 wt.% LaMA + 40 wt.% YSZ (60LaMA + 40YSZ) intermediate composite layer with the highest thermal expansion coefficient than other composite layers generating higher internal stress level to the tri- and six-layer TBCs, different bond coat temperature and TGO growth, as well as long-term stability of the LaMA coating during thermal cycling tests, were characterized and compared to understand the different thermal cycling lifetime and failure modes among such three multilayer TBCs.

Effects of gradient transitional layer on thermal cycling life and failure of LaZrCeO/YSZ thermal barrier coatings

Abstract The present work focuses on investigation of the effects of gradient transitional layer (GTL) on thermal cycling life and failure behavior of LaZrCeO/YSZ thermal barrier coatings. Characterization of microstructure evolution is implemented using correlative methods, which links together the observations and analysis from X-ray diffraction, scanning electron microscopy and transmission electron microscopy. The LaZrCeO/YSZ with GTL showed relatively good thermal cycling life and thermal stability. After thermal cycles, Cr element diffuses out and concentrates in LaZrCeO layer. The crack evolution, diffusion behavior and thermal stability are the key factors for the good thermal cycling life and failure mechanism of LaZrCeO/YSZ.

LZC/YSZ double layer coatings: EB-PVD, microstructure and thermal cycling life

Abstract Low thermal conductivity ceramic materials have triggered tremendous attention in gas turbine engines coatings. It still remains a challenge for investigating the thermal cycling life, diffusion and failure of LaZrCeO (LZC). A LZC/YSZ double layer coatings (DCL) TBCs have been prepared by vacuum arc ion-plating (ARC) and electron beam-physical vapor deposition (EB-PVD). The phase structures of LZC/YSZ TBCs are composed of La2Zr2O7 and La2Ce2O7. The as-deposited LZC/YSZ shows columnar and feathery microstructures. The as-deposited coating showed high thermal cycling and shock lifetime. After thermal cycles, the DCL coating shows a good thermal stability. The double layer structure and feathery microstructure appear to be relevant with the high lifetime of TBCs.

Reliability of fine-pitch through-vias in glass interposers and packages for high-bandwidth computing and communications

Glass is an ideal substrate material to enable 2.5D and 3D packaging of ICs at low cost and high performance. However, it is a brittle material and is prone to failures during fabrication and operation. Large coefficient of thermal expansion (CTE) mismatch between copper and glass leads to thermomechanical stresses that can lead to glass cracking and delamination from glass interfaces. This paper focuses on modeling and reliability characterization of copper-plated through-package-vias (TPV) in glass packages. Thermomechanical simulations were carried out to obtain design guidelines for reliable TPVs in glass. Test-vehicles with different glass thicknesses and copper TPV fabrication conditions were fabricated for thermal cycling tests, resistance monitoring and failure analysis. The reliability characterization results showed good thermomechanical reliability of TPVs in ultra-thin glass panels.

Thermal cycling life and failure analysis of rare earth magnesium hexaaluminate based advanced thermal barrier coatings at 1400 °C

Abstract Thermal cycling lifespan of novel rare earth magnesium hexaaluminate (REMHA) based thermal barrier coatings (TBCs) such as lanthanum magnesium hexaaluminate (LMHA), neodymium doped LMHA (LNMHA) and LNMHA-yttrium aluminium garnet (YAG) composite was tested using gas burner rig operating at 1400 °C. A standard TBC of yttria stabilized zirconia used as a reference was also tested under similar conditions. The failure mechanism of these coatings was also investigated. The REMHA based coatings have shown much higher life as compared to YSZ coating. LNMHA coating was found to last longer i.e., completed 7851 cycles (almost 916 h) which is 2.7 and 4.2 times higher than the parent LMHA and YSZ coatings, respectively. Thermal expansion coefficient and fracture toughness of the ceramic top coat play a vital role and determine the type of failure. LNMHA coating seems to be a promising candidate for advanced TBCs operating at temperature as high as 1400 °C.

Characterization and thermal cycling behavior of La2(Zr0.7Ce0.3)2O7/8YSZ functionally graded thermal barrier coating prepared by atmospheric plasma spraying

A five-layer ceramic-ceramic functionally graded thermal barrier coating (FG-TBC) of La2(Zr0.7Ce0.3)2O7 (LZ7C3) and 8YSZ has been prepared by atmospheric plasma spraying. The thermal expansion coefficients (TECs) of the five ceramic layers of the graded coating from top layer to the inner layer are gradually increased. Thermal cycling behavior and failure mechanism of the coating have been studied. The abnormal oxidation of the bond coat and sintering of the LZ7C3 are the primary factors for the spot spallation of the graded coating. The effects of thermal expansion mismatch also accelerate the spot spallation. The spallation at the edge of the coating is due to the effect of thermal expansion mismatch and thermal stress produced during thermal cycling.