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Effect of flame conditions on abrasive wear performance of HVOF sprayed nanostructured WC-12Co coatings

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中国有色金属学会会刊：英文版 2004年第z1期14卷 72-76页

作者： wang yu-yue li chang-jiu MA Jian yang guan-jun State Key Laboratory for Mechanical Behavior of Materials Xi''an Jiaotong University Xi''an 710049 China State Key Laboratory for Mechanical Behavior of MaterialsXi''an Jiaotong University Xi''an 710049 China State Key Laboratory for Mechanical Behavior of MaterialsXi''an Jiaotong University Xi''an 710049 China State Key Laboratory for Mechanical Behavior of MaterialsXi''an Jiaotong University Xi''an 710049 China

Nanostructured WC-12Co coatings were deposited by high velocity oxy-fuel (HVOF) spraying with an agglomerated powder. The effect of flame conditions on the microstructure of the nanostructured coatings was investigated. The wear properties of the coatings were characterized using a dry rubber-wheel wear test. The results show that the nanostructured WC-Co coatings consist of WC, W2C, W and an amorphous binder phase. The microstructure of the coating is significantly influenced by the ratio of oxygen flow to fuel flow. Under the lower ratio of oxygen/fuel flow, the nanostructured coating presents a relative dense microstructure and severe decarburization of WC phase occurs during spraying. With increasing ratio of oxygen/fuel flow, the bonding of WC particles in the coating becomes loose resulting from the original structure of feedstock and the decarburization of WC becomes less owing to limited heating to the powder. Both the decarburization of WC particles in spraying and the bonding among WC particles in the coatings affect the wear performance. The examination of the worn surfaces of the nanostructured coatings reveals that the dominant wear mechanisms would be spalling from the interface of WCCo splats when spray particles undergo a limited melting. While the melting state of the spray particles is improved,the dominant wear mechanisms become the plastic deformation and plowing of the matrix and spalling of WC particles from the matrix.

关键词： high velocity oxy-fuel spraying nanostructure abrasive wear performance WC-Co coating

Improving WC-Co coating adhesive strength on rough substrate:Finite element modeling and experiment

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Journal of Materials Science & Technology 2020年第2期37卷 1-8页

作者： Adnan Tahir guang-Rong li Mei-jun liu guan-jun yang Cheng-Xin li yu-yue wang chang-jiu li State Key Laboratory for Mechanical Behavior of Materials School of Materials Science and EngineeringXi’an Jiaotong UniversityXi’an710049China

The adhesive strength in a coating-substrate system is of primary importance for the coating lifetime in ***,the underlying mechanism is not fully understood due to the complex internal structure of composite *** this study,the effect of substrate roughness on the adhesive strength of WCCo coatings was investigated by experiment and *** show that the adhesive strength is significantly affected by the *** the case of the Rachanged from concentrated state to widespread state,which decreases the critical stress to result in crack ***’s why a larger roughness can cause a higher adhesive *** study gives understanding on the mechanism of adhesive strength affected by roughness,which contributes to the parameter optimization with better performance.

关键词： Adhesive strength Roughness lifetime Simulation XFEM Residual stress

Critical scale grain size for optimal lifetime of TBCs

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Journal of Materials Science & Technology 2022年第20期115卷 241-250页

作者： lin Chen Guo-Hui Meng chang-jiu li guan-jun yang State Key Laboratory for Mechanical Behavior of Materials School of Materials Science and EngineeringXi’an Jiaotong UniversityXi’an 710049China

Thermal barrier coatings(TBCs)suffer from spalling failure resulting from the rapid growth of thermally grown oxides(TGO)on the metallic bond *** this study,to achieve the optimal lifetime of TBCs,a lifetime phase diagram was constructed for the entire service of ***,both the thermal mismatch stress during thermal cycling and the TGO growth stress during thermal exposure were ***,thickening behavior of the Al_(2)O_(3) scale related to grain size was ***,transverse delamination failure due to the thermal mismatch stress was ***,vertical cracking failure related to early scale growth was ***,a critical scale grain size of~2.5μm was identified for achieving the optimal lifetime of *** was experimentally proved that vertical cracking of the Al_(2)O_(3) scale occurred during early oxidation as the scale grain size was larger than~4μm after *** proposed lifetime phase diagram and critical scale grain size effect serve as novel criteria for the design of next-generation durable TBCs.

关键词： TGO growth Grain size Grain boundaries Channel cracking Service lifetime

Achieving the high phase purity of CH_3NH_3PbI_3 film by two-step solution processable crystal engineering

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Journal of Materials Science & Technology 2018年第8期34卷 1405-1411页

作者： Yan li Bin Ding guan-jun yang chang-jiu li Cheng-Xin li State Key Laboratory for Mechanical Behavior of Materials School of Materials Science and EngineeringXi'an Jiaotong University

To date, it is still a great challenge for highly efficient perovskite devices to realize the high quality per- ovskite films with high purity, high coverage ratio and good crystallization by two-step scalable solution method. In this study, a series PbI2 films with tunable micro-architecture of Pbl2 crystals are prepared via solution processable crystal engineering. The perovskite film, prepared by optimized pit spacing in gas pumped PbI2 film at 1000 Pa, shows the highest film quality, including no residual Pbl2 phase, compact morphology, and improved photoluminescence intensity. A transformation kinetics shows that the pit spacing strongly influences both the mass transfer and the sequential intercalation reaction between CH3NH31 and PbI2 crystals, which ultimately determines the full reaction state of the perovskite film. The perovskite solar cells assembled by the perovskite film show both high power-conversion efficiency and good reproducibility of photovoltaic performance due to the restrained charge recombination arising from the high quality perovskite film.

关键词： High phase purity CHHNH3PbI3 film Two-step solution method Perovskite solar cells

Realizing the excellent oxidation resistance of an environmental barrier coating through aluminum surface modification

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Journal of Advanced Ceramics 2024年第7期13卷 976-986页

作者： lin Dong Wen-Qi yang lin Chen guan-jun yang chang-jiu li State Key Laboratory for Mechanical Behavior of Materials School of Materials Science and EngineeringXi’an Jiaotong UniversityXi’an 710049China Xi’an Aerospace Engine Company limited in China Aerospace Science and Technology Corporation Xi’an 710065China

The lifetime of Si-based environmental barrier coatings(EBCs)is constrained by thermally grown SiO_(2)oxidelayer(SiO_(2)-TGO),which can cause premature cracking and *** address this issue,a new approach for surfacemodification using aluminum is *** oxidation performance was examined in a 50 vol%H_(2)O-50 vol%O_(2)environment at 1350℃for up to 300 *** results indicate that a dense ytterbium aluminum garnet(YbAG)layer wasformed after modification,decreasing the porosity by 80%.Due to the elimination of fast diffusion channels and the lowoxygen permeability of YbAG,aluminum modification significantly reduced the growth rate of SiO_(2)-TGO by nearly twoorders of ***,its thickness decreased by more than 70%after 300 h of exposure.A diffusioncontrolled oxidation mechanism indicates that the modified dense surface is equivalent to an initial SiO_(2)layer with a specificthickness,causing a shift in the oxidation time and increasing the oxidation *** research provides valuableinsights for designing Si-based EBC with improved lifetimes.

关键词： environmental barrier coating(EBC) oxidation modification diffusion cracking

Heterogeneous layered structure in thermal barrier coatings by plasma spray-physical vapor deposition

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Journal of Advanced Ceramics 2023年第2期12卷 386-398页

作者： Yan-Hong LU Lu HUANG Mei-jun liU guan-jun yang chang-jiu li State Key Laboratory for Mechanical Behavior of Materials School of Materials Science and EngineeringXi’an Jiaotong UniversityXi’an 710049China

The unique columnar structure endows thermal barrier coatings(TBCs)prepared by plasma spray-physical vapor deposition(PS-PVD)with high thermal insulation and long ***,the coating delamination failure resulting from an intra-column fracture(within a column rather than between columns)is a bottleneck in the solid dust particle impact environment for *** clarify the intra-column fracture mechanism,a basic layer deposition model is developed to explore a heterogeneous weak-to-strong layered structure formed by a local transient in-situ deposit *** the PS-PVD,an in-situ deposit surface is continuously updated due to constantly being covered by vapor condensation,showing a transient temperature,which means that the in-situ deposit surface temperature rises sharply in short period of 0.2 s of depositing a thin layer during a single ***,the increasing temperature of the in-situ deposit surface results in an experimentally observed heterogeneous weak-to-strong structure,showing a continuous transition from a porous weak structure at the bottom region to a dense strong structure at the top *** structure easily makes the intra-column fracture at the porous weak *** results shed light on improving TBC lifetime by restraining the intra-column fracture.

关键词： transient temperature in-situ deposit surface heterogeneous layered structure fracture mechanism plasma spray-physical vapor deposition(PS-PVD)

Durable dual-state duplex Si-HfO_(2)with excellent oxidation and cracking resistance

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Journal of Advanced Ceramics 2024年第3期13卷 388-401页

作者： lin Chen Jing-Chuan Luo Wen-Qi yang chang-jiu li guan-jun yang State Key Laboratory for Mechanical Behavior of Materials School of Materials Science and EngineeringXi’an Jiaotong UniversityXi’an 710049China Xi’an Aerospace Engine Company limited in CASC Xi’an 710065China

The lifetime of Si bond coatings in environmental barrier coatings is constrained by phase-transition-induced cracking of the SiO_(2)*** this study,Si-HfO_(2)dual-state duplex composite materials are proposed to address this issue by partially forming HfSiO_(4)and minimizing the SiO_(2)*** as-prepared composite exhibited a structure comprising discrete HfO_(2)“bricks”embedded in a continuous Si“mortar”,while the oxidized state transformed into discrete HfSiO_(4)“bricks”within continuous thin SiO_(2)“mortars”.The results indicate that continuous thin SiO_(2)contributes to reducing the oxidation rate to a level comparable to that of pure Si,and discrete HfSiO_(4)particles aid in relieving phase transition-induced stress and inhibiting crack propagation,thereby enhancing oxidation and cracking resistance ***,the composite with 20 mol%HfO_(2)and a mean particle size of~500 nm at 1370℃exhibited a service lifetime 10 times greater than that of pure *** research provides valuable insights for designing Si-based bond coatings with improved service lifetime.

关键词： oxidation environmental barrier coatings(EBCs) phase transition cracking bond coatings

Tailoring sintering-resistant thermal barrier coatings by considering critical healing width of two-dimensional interlamellar pores

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Journal of Advanced Ceramics 2023年第7期12卷 1317-1330页

作者： guang-Rong li Tao liu Xiao-Tao Luo guan-jun yang chang-jiu li State Key Laboratory for Mechanical Behavior of Materials School of Materials Science and EngineeringXi'an Jiaotong UniversityXi'an 710049China

Large degradation in thermal insulation and strain tolerance is a main headache and a primary cause of the failure for plasma-sprayed thermal barrier coatings(TBCs)during *** mechanism behind such degradation is the healing of interlamellar pores formed by multiple connections between edges of a pore,which significantly speeds up healing during thermal *** objective of this study is to obtain sintering-resistant TBCs by tailoring the width of interlamellar pores to avoid multiple ***,the mechanism responsible for the multiple connections was *** splat surfaces before and after thermal treatments were characterized via an atomic force microscope(AFM).The roughening of the pore surface occurs during thermal exposure,along with the grain growth inside the ***,the local surface height increases,which causes multiple connections and healing of the interlamellar ***,critical widths of the interlamellar pores for avoiding the multiple connections during thermal exposure are established by correlating the extent of surface roughening with the growth of individual *** height increase of the splat surface and the growth of the grain size(D)were found to increase with the exposure temperature and duration.A relationship linking the height increase and the growth of the grain size induced by thermal exposure in plasma-sprayed ceramic splats was ***,composite TBCs were prepared to form wide interlamellar pores in the *** this design,the increases in the thermal conductivity(λ)and the elastic modulus(E)can be prevented to a large ***,sintering-resistant TBCs that maintain high thermal insulation and strain tolerance,even afer long thermal exposure,can be created.

关键词： thermal barrier coatings(TBCs) air plasma spraying(APS) multiple connections grain growth sintering-resistant structure

lightweight epoxy-based abradable seal coating with high bonding strength

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Journal of Materials Science & Technology 2021年第10期69卷 129-137页

作者： yun-Qi Tong Qiu-Sheng Shi Mei-jun liu guang-Rong li chang-jiu li guan-jun yang State Key Laboratory for Mechanical Behavior o f Materials School of Materials Science and EngineeringXi'an Jiaotong UniversityXi'an710049China

To gain high efficiency and low fuel consumption, aluminum-based abradable seal coatings had been widely used in the compressor casing of aero engines or gas turbines owing to the low elastic modulus. However, the adhesive transfer phenomenon frequently occurs when the radial rubbing generates between titanium alloy blade tips and aluminum-based coating. It tends to increase scratch force and results in blades vibration and even engine jam. To eliminate this problem, a new lightweight epoxy-based abradable seal coating with high bonding strength was developed by an effective and porosity controllable mixing process that distributes spherical pores uniformly in the continuous matrix. A lightweight coating of 63% porosity with a hardness of 33.1(HR15 Y) can be reached when the content of hollow microspheres is 31 wt.%. The coating density is 0.5 g/cm3 and the bonding strength is as high as 18 *** performance of the epoxy-based coating is comprehensively better than aluminum-based coatings in five essential indices. This study is expected to provide a new technical path for obtaining high-quality abradable seal coatings to guarantee the efficient and safe operation of compressors.

关键词： Epoxy-based seal coating Porosity HR15Y lightweight High bonding strength