Liang Wang

Bio: Liang Wang is an academic researcher from Chinese Academy of Sciences. The author has contributed to research in topics: Thermal barrier coating & Coating. The author has an hindex of 16, co-authored 24 publications receiving 766 citations. Previous affiliations of Liang Wang include Harbin Institute of Technology.

Modeling of thermal properties and failure of thermal barrier coatings with the use of finite element methods: A review

Abstract: To understand the thermal insulation and failure problems of the thermal barrier coatings (TBCs) deeply is vital to evaluate the reliability and durability of the TBCs. Actually, experimental methods can not reflect the real case of the TBCs during its fabrication and service process. Finite element modeling (FEM) play an important role in studying these problems. Especially, FEM is very effective in calculating the thermal insulation and the fracture failure problems of the TBCs. In this paper, the research progress of the FEM on the study of the thermal insulation and associated failure problems of the TBCs has been reviewed. Firstly, from the aspect of the investigation of the heat insulation of the TBCs, the thermal analysis via FEM is widely used. The effective thermal conductivity, insulation temperature at different temperatures of the coating surface considering the thermal conduct, convection between the coating and the environment, heat radiation at high temperature and interfacial thermal resistance effect can be calculated by FEM. Secondly, the residual stress which is induced in the process of plasma spraying or caused by the thermal expansion coefficient mismatch between the coating and substrate and the temperature gradient variation under the actual service conditions can be also calculated via FEM. The solution method is based on the thermal–mechanical coupled technique. Thirdly, the failure problems of the TBCs under the actual service conditions can be calculated or simulated via FEM. The basic thought is using the fracture mechanic method. Previous investigation focused on the location of the maximum residual stress and try to find the possible failure positions of the TBCs, and to predict the possible failure modes of the TBCs. It belonged to static analysis. With the development of the FEM techniques, the virtual crack closure technique (VCCT), extended finite element method (XFEM) and cohesive zone model (CZM) have been used to simulate the crack propagation behavior of the TBCs. The failure patterns of the TBCs can be monitored timely and dynamically using these methods and the life prediction of the TBCs under the actual service conditions is expected to be realized eventually.

Effects of inorganic sealant and brief heat treatments on corrosion behavior of plasma sprayed Cr2O3–Al2O3 composite ceramic coatings

Abstract: In the present study, Cr2O3–Al2O3 composite coatings were fabricated by atmospheric plasma spraying (APS) technique. Aluminum phosphate with small fraction of Al2O3 nanoparticles was applied as high-temperature sealant to enhance the anti-corrosion performance of the coatings. The inorganic sealant significantly reduced the open pore of the as-sprayed coatings and showed low shrinkage after heat treatment (600 °C, 30 min). Potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) and salt spray tests were used to assess anti-corrosive characteristics of the coatings. The sealants resulted in an augment of corrosion resistance properties of the coatings both before and after heat treatment, indicating effective sealing and good high temperature applicability. The sealed Cr2O3–Al2O3 composite coatings have a potential use in severe corrosion condition.

Thermal shock behaviors of YSZ thick thermal barrier coatings fabricated by suspension and atmospheric plasma spraying

Abstract: Thick thermal barrier coating (TTBC) having segmentation-crack structure is favorable to its durability under severe thermal shock conditions. The present study reports the results of a comparative study on the thermal shock behavior of yttria-stabilized zirconia (YSZ) TTBCs with the segmentation-crack structure fabricated using axial suspension plasma spraying (ASPS) and atmospheric plasma spraying (APS) processes, respectively. The evolution of the microstructures, the phase composition and the failure behavior of both TTBCs before and after the thermal shock tests were investigated. Microstructure analysis showed that both the APS and ASPS coatings possessed typical segmentation cracks in the through-thickness direction, the measured segmentation crack densities ( Ds ) of the APS and ASPS YSZ top coat were about 2.5 cracks mm − 1 and 4 cracks mm − 1 , respectively. The microstructure analysis also showed an evenly spaced horizontal crack structure for the ASPS coating instead of the large columnar and eliminated splats boundaries structure for the APS coating. During thermal shock cycling, the spallation life of the ASPS TTBCs was improved by a factor of about 2 compared with that of APS coatings. Failure of the APS coatings is due to the fringe segments spallation, but in addition to the fringe segments spallation, a different center segment pull-out spallation can also be detected in the ASPS coatings.

Nanocomposite Coatings: Preparation, Characterization, Properties, and Applications

Abstract: Incorporation of nanofillers into the organic coatings might enhance their barrier performance, by decreasing the porosity and zigzagging the diffusion path for deleterious species. Thus, the coatings containing nanofillers are expected to have significant barrier properties for corrosion protection and reduce the trend for the coating to blister or delaminate. On the other hand, high hardness could be obtained for metallic coatings by producing the hard nanocrystalline phases within a metallic matrix. This article presents a review on recent development of nanocomposite coatings, providing an overview of nanocomposite coatings in various aspects dealing with the classification, preparative method, the nanocomposite coating properties, and characterization methods. It covers potential applications in areas such as the anticorrosion, antiwear, superhydrophobic area, self-cleaning, antifouling/antibacterial area, and electronics. Finally, conclusion and future trends will be also reported.

Modeling of thermal properties and failure of thermal barrier coatings with the use of finite element methods: A review

Abstract: To understand the thermal insulation and failure problems of the thermal barrier coatings (TBCs) deeply is vital to evaluate the reliability and durability of the TBCs. Actually, experimental methods can not reflect the real case of the TBCs during its fabrication and service process. Finite element modeling (FEM) play an important role in studying these problems. Especially, FEM is very effective in calculating the thermal insulation and the fracture failure problems of the TBCs. In this paper, the research progress of the FEM on the study of the thermal insulation and associated failure problems of the TBCs has been reviewed. Firstly, from the aspect of the investigation of the heat insulation of the TBCs, the thermal analysis via FEM is widely used. The effective thermal conductivity, insulation temperature at different temperatures of the coating surface considering the thermal conduct, convection between the coating and the environment, heat radiation at high temperature and interfacial thermal resistance effect can be calculated by FEM. Secondly, the residual stress which is induced in the process of plasma spraying or caused by the thermal expansion coefficient mismatch between the coating and substrate and the temperature gradient variation under the actual service conditions can be also calculated via FEM. The solution method is based on the thermal–mechanical coupled technique. Thirdly, the failure problems of the TBCs under the actual service conditions can be calculated or simulated via FEM. The basic thought is using the fracture mechanic method. Previous investigation focused on the location of the maximum residual stress and try to find the possible failure positions of the TBCs, and to predict the possible failure modes of the TBCs. It belonged to static analysis. With the development of the FEM techniques, the virtual crack closure technique (VCCT), extended finite element method (XFEM) and cohesive zone model (CZM) have been used to simulate the crack propagation behavior of the TBCs. The failure patterns of the TBCs can be monitored timely and dynamically using these methods and the life prediction of the TBCs under the actual service conditions is expected to be realized eventually.

A review of testing methods for thermal spray coatings

Abstract: The primary focus of this review concerns the test methods used to evaluate thermal spray coatings. Techniques to measure coating intrinsic properties such as (i) porosity and (ii) residual stress state; as well as extrinsic mechanical properties that include (iii) hardness, (iv) adhesion, (v) elastic modulus, (vi) fracture toughness, and (vi) the Poisson’s ratio of thermal spray coatings are presented. This review also encompasses the feedstock and thermal spray method since process variants create a specific microstructure. An important aspect of this work is to highlight the extrinsic nature of mechanical property measurements with regard to thermal spray coatings. Thermal spray coatings exhibit anisotropic behaviour and microstructural artefacts such as porosity and the splat structure of coatings influence the mechanical characterisation methods. The analysis of coating data variability evolving from the different measurement techniques is of particular relevance to interpret the character of...