| 1. |
|
|
| 2. |
- Yuan, Kang, et al.
(författare)
-
Hot corrosion of MCrAlY coatings in sulphate and SO2 environment at 900°C : Is SO2 necessarily bad?
- 2015
-
Ingår i: Surface & Coatings Technology. - : Elsevier BV. - 0257-8972 .- 1879-3347. ; 261, s. 41-53
-
Tidskriftsartikel (refereegranskat)abstract
- MCrAlY coatings can be corroded due to the basic fluxing (type-I hot corrosion) of the supposed-to-be protective alumina scale in a molten sulphate environment. In this study, two MCrAlY coatings, coating A (10wt.% Al, 20wt.% Cr) and coating B (7wt.% Al, 28wt.% Cr), were tested in 48-hour cycles at 900°C in a sodium-potassium sulphate environment with and without SO2 (500ppm). The aim was to study the effect of SO2 at the typical type-I-hot-corrosion temperature-900°C. The results showed that the corrosion behavior of the MCrAlY coatings depended not only on the coating composition but also on the corrosion environment. It was found that in coating A alumina scale was more resistant in the sulphate-plus-SO2 condition than that in the sulphate-only condition. Such phenomenon indicated a beneficial effect of SO2. On Coating B, however, mixed oxide layers, consisting of alumina and other oxides and sulfides, formed after a certain number of cycles in the sulphate environments with or without SO2 gas. In this coating, the addition of SO2 in the sulphate environment promoted the formation of non-dense chromia oxides which may form from oxidation of Cr-sulfides.
|
|
| 3. |
- Ding, Yang, et al.
(författare)
-
Artificial intelligence-assisted point-of-care testing system for ultrafast and quantitative detection of drug-resistant bacteria
- 2024
-
Ingår i: SMARTMAT. - : WILEY. - 2766-8525. ; 5:3
-
Tidskriftsartikel (refereegranskat)abstract
- As one of the major causes of antimicrobial resistance, beta-lactamase develops rapidly among bacteria. Detection of beta-lactamase in an efficient and low-cost point-of-care testing (POCT) way is urgently needed. However, due to the volatile environmental factors, the quantitative measurement of current POCT is often inaccurate. Herein, we demonstrate an artificial intelligence (AI)-assisted mobile health system that consists of a paper-based beta-lactamase fluorogenic probe analytical device and a smartphone-based AI cloud. An ultrafast broad-spectrum fluorogenic probe (B1) that could respond to beta-lactamase within 20 s was first synthesized, and the detection limit was determined to be 0.13 nmol/L. Meanwhile, a three-dimensional microfluidic paper-based analytical device was fabricated for integration of B1. Also, a smartphone-based AI cloud was developed to correct errors automatically and output results intelligently. This smart system could calibrate the temperature and pH in the beta-lactamase level detection in complex samples and mice infected with various bacteria, which shows the problem-solving ability in interdisciplinary research, and demonstrates potential clinical benefits.
|
|
| 4. |
- Yuan, Kang, 1987-
(författare)
-
Oxidation and Corrosion of New MCrAlX Coatings : Modelling and Experiments
- 2014
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- MCrAlY coatings (“M” for Ni and/or Co) are widely used for the protection of superalloy components operated at high temperatures such as in the hot sections of gas turbines. The exposure to high temperature can cause coating degradation due to oxidation or hot corrosion at the coating surface. Microstructures in the coating and the coating life are affected also by the diffusion of alloying elements through the coating-superalloy interface. This PhD project, by applying thermodynamic modelling and experimental tests, investigates the oxidation and hot corrosion behavior of new MCrAlX coatings, in which X, referring to minor elements, is used to highlight the functions of such elements.In order to understand and predict the coating degradation progress during thermal exposure, an oxidation-diffusion model has been established for MCrAlX coating-superalloy systems, which integrates the oxidation of aluminum at coating surface, diffusion of alloying elements, and the diffusion-blocking effect in the materials. The predicted chemical composition profile and microstructure agreed well with experimental results in a CoNiCrAlYSiTa-Inconel 792 system. The model was further applied in several coating-superalloy systems to study the influence of coating composition, superalloy composition and temperature on the evolution of microstructure in the coating and the coating life. The results have demonstrated the potential of the model in designing new durable MCrAlX coatings. In addition to the applications in coating-superalloy systems, the model was also adapted for studying the microstructural development in a superalloy in which internal oxidation and nitridation occurred in an oxidation process.The oxidation behavior of some HVOF MCrAlX coatings was studied by thermal exposure at different temperatures (900, 1000, 1100 °C). Different spinels formed above the alumina scale, depending on the oxidation temperature. The minor alloying elements, Ru and Ir, had no direct influence on the oxidation behavior but may affect the phase stability in the coating.MCrAlX coatings were also tested in 48-hour cycles at 900 °C in different hot corrosion environments containing sulphates and/or SO2. The results showed that the coating performance was dependent on coating quality, concentration of Al and Cr in the coating, and the hot corrosion condition. It was also found that the addition of SO2 in the environment may not necessarily be bad for hot corrosion resistance of some MCrAlY coatings.
|
|
| 5. |
- Yuan, Kang, et al.
(författare)
-
Some aspects of elemental behaviour in HVOF MCrAlY coatings in high-temperature oxidation
- 2015
-
Ingår i: Surface & Coatings Technology. - : Elsevier BV. - 0257-8972 .- 1879-3347. ; 261, s. 86-101
-
Tidskriftsartikel (refereegranskat)abstract
- MCrAlY coatings are widely used to protect superalloys against oxidation and corrosion at high temperature in gas turbine engines. To design a durable MCrAlY coating, the elemental behaviour in coating-superalloy couples needs to be better understood. After oxidation tests in temperature range between 900 °C to 1100 °C, the microstructural development in the samples were analysed. The investigation was mainly focused on the microstructures at the coating surface or in areas near the coating-superalloy interface. Some interdiffusion simulations were also done to model the diffusion behaviour of alloying elements in different coatingsuperalloy couples. The results showed that both oxidation at the coatings’ surfaces and the elements’ diffusion inside of the materials were temperature- and chemical-composition dependent. The behaviour of some minor elements like Y, Hf, Ru and Ir in the oxidation processes was particularly studied by tracking their position and composition in the materials.
|
|
| 6. |
- Yuan, Kang
(författare)
-
Thermal and Mechanical Behaviors of High Temperature Coatings
- 2013
-
Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- With superior oxidation and corrosion resistance, metallic coatings (i.e. diffusion coatings and MCrAlX coatings) are widely used to protect hot components made of superalloys in turbine engines. Two issues are critically important for the coating at high temperatures: thermal property related to oxidation/corrosion behavior and microstructure stability, and mechanical properties (e.g. creep and fatigue). The aim of this project is to develop better understanding of the thermal and mechanical behaviors of metallic coatings on superalloys and to improve the accuracy of prediction of their lifetime by thermodynamic modeling. The present work includes an investigation on the oxidation behavior of MCrAlX coating with a new lifetimeprediction model and a study on the influence of diffusion coatings on creep and fatigue behaviors of the superalloy IN792.Experiments on isothermal and thermal cycling oxidation were designed to investigate the oxidation behavior of a HVOF CoNiCrAlYSi coating on superalloy IN792. It is found that the oxidation behaviors of the coating are related to its thermodynamic property. A diffusion model has been established using the homogenization models in the DICTRA software and taking into consideration of the influence of surface oxidation, coating-substrate interdiffusion and diffusion blocking effect caused by internal voids and oxides. The simulation results show an improved accuracy of lifetime prediction by introducing the diffusion blocking effect.Microstructural evolution during creep process at high temperatures was studied in different diffusion coatings (NiAl and PtAl). It is found that the inward diffusion of aluminum controls the thickening rate of the diffusion coatings. The developed coatings displayed two types of mechanical behavior - being easily plasticized or cracked - dependent on temperature and type of coating, and therefore could be considered as non-load carrying material during creep test. The influence of cracking of PtAl coating on the high-cycle fatigue (HCF) behavior of the IN792 was also investigated. The results show that precracking of the coating prior to the fatigue test has little influence on the fatigue limit of specimens with thin coating (50 μm) but lowers the fatigue limit of specimens with thick coating (70 μm). The through-coating crack has enough mobility to penetrate into the substrate and causes fatigue failure only when the driving force for crack propagation is increased above a critical value due to a higher applied stress or a larger crack length (thicker coating).
|
|
