Effects of Additive CeO_2 on Thermal Shock Resistance of Plasma-Sprayed Cr_2O_3 Coating

The influence of CeO2 with different content on the thermal shock resistance of plasmasprayed Cr2O3 coating was investigated. The thermal shock failure mechanism of coating was also studied. It is found that the thermal shock failure mechanism of coating is thermal stress fatigue destruction, and the destruction takes place at interface of ceramic and bond coating. The experimental results show that the lifetime of coating fracture and failure increase considerably when 3% CeO2 is added into the plasma-sprayed Cr2O3 coating. The suitable content of CeO2 makes the microcracks exist in network form. The microcrack net can release internal stress in coating, delay the crack forming and expanding and decrease holes in coating. Thus the thermal shock resistance increase largely.

Structure of Plasma-sprayed ZrO_2/(Ni/AI)Interface

The structures of plasma-sprayed ZrO_2/(Ni/AI) interface before and after hot isostatic pressing (HIP) treatment were studied by TEM,ED and X-ray diffraction analysis.Plasma-sprayed ZrO_2/(Ni/AI) interfacial region is of definite thickness and consists of multi-phase structures. Amorphous ZrO_2 sublayer,amorphous plus microcrystalline ZrO_2 sublayer and NiO were found in the interface.NiO phase formed by the reaction between ceramic coating and metallic substrate in local regions.However.the thickness and amount of NiO trended to increase and the distribution of NiO particles trended continuously when the coating was subjected to HIP treatment.HIP treatment can accelerate the diffusion of atoms in the interfacial region.

Microstructures and Adhesive Strength of Three Kinds of Ceramic Coatings

In gas turbine engine, the study of ceramic thermal resistance coating has always been paid more attention because it can effectively reduce metal interface temperatures, improve corrosion and/or oxidation resistance and extend life. The microstructures, SEM microfractographs and adhesive strength of three kinds of zirconia plasma-sprayed ceramic coating were investigated. The results indicated that nanostructured zirconia coating have higher adhesive strength and better micro-cracking resistance properties compared with magnesia or yttria stabilized zirconia coating because its less quantities laminar internal structures and closed packed structures with less quantities and uniform distribution cavities. The sprayed power is also an important factor affecting adhesive strength of nanostructured zirconia coating.

Advancing knowledge of plasma spraying coatings for Li||Sb-Sn liquid metal batteries by X-ray micro-CT

The performance of Li||Sb-Sn liquid metal batteries(LMBs) is hindered by the corrosion of the Sb-Sn cathode on its current collector. Herein, a uniform, dense, and low-oxidized W coating was prepared by plasma spraying, which can effectively resist the corrosion of the cathode and improve the cycle stability of the Li||Sb-Sn LMBs. For the first time, micro-CT nondestructive inspection is applied in the field of LMBs. The corrosion micromorphology and composition evolution of the SS304 matrix and Sb-Sn cathode with or without the plasma-sprayed W coating is obtained without disassembling the battery, which proves that the W coating can effectively protect the SS304 matrix. Our autonomous new LMB device for nondestructive inspection is universal and can be applied to different LMBs systems for advancing knowledge of corrosion mechanism and protection. This work guarantees the ability to directly visualize the inner critical positions in three dimensions and fills the knowledge gap in the field of LMB detection technology.

Preparation and Microstructure of ZrO_2-MoSi_2 Composite Powder and Compound Coating

In order to improve the lifetime of continuous casting,ZrO_2-MoSi_2 composite powder used for plasmaspraying was prepared via spray drying and vacuum sintering.The microstructure and characteristics of the powder were investigated by particle size analysis,scanning electron microscopy and X-ray diffraction,respectively.The results show that the average viscosity and settlement rate are 60.43 mPas and 1.86%,respectively,when adding ammonium polyacrylate as a dispersant and polyvinyl alcohol as a binder.The powder obtained at the solid content of 70 wt.%,the dispersant amount of 1wt.%,the binder of 10 wt.%,and the sintering temperature of 1200 "C has the spherical agglomerate and a moderate size,which can be melted on the composite coating surface with a good compactness via plasma-spraying.

Influences of Laser Powers on Microstructure and Properties of the Al-Si/Al+Al_2O_3 Coating on the AZ91D Magnesium Alloy

An Al-Si/Al+Al2O3 coating was prepared on an AZ91D Mg alloy substrate by laser cladding of the plasma-sprayed coating.X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used to identify the phases and to study the morphology,respectively.The adhesion strength and the porosity ratio of the coating were measured by using a tensile testing machine and an optical microscope (OM),respectively.The microhardness was measured using a micro Vickers hardness tester.The results show that after laser cladding,the adhesion strength of the coating increased from 10.78 to 25.17 MPa.When the laser power was 1400W,the metastable γ-Al2O3 phase in the coating transformed completely into the stable α-Al2O3 phase.Along with the increase of the laser power,the porosity ratio of the coating decreased.But when the laser power was over 1400W,the porosity ratio increased.The microhardness of the surface was the hardest which was improved from HV0.05125 to HV0.05221.The larger the power of the laser was,the harder the coating was.But when the power was 1600W,the microhardness increased slightly,even the microhardness of the internal decreased.