Characterization and Erosion Behavior of Plasma Sprayed NiCrAlY and Ni-20Cr Coatings on an Fe-based Superalloy

2006 ◽  
Vol 128 (3) ◽  
pp. 469-475 ◽  
Author(s):  
S. B. Mishra ◽  
K. Chandra ◽  
S. Prakash
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Erosion Rate ◽  
Elevated Temperatures ◽  
Impingement Angle ◽  
Contributing Factors ◽  
Air Jet ◽  
Nicraly Coating ◽  
Plasma Sprayed ◽  
Scanning Electron

Degradation of materials due to solid particle erosion is encountered in a variety of engineering industries, either at room temperature or elevated temperatures. Nickel-based coatings are commonly used in applications where wear resistance, combined with oxidation or hot corrosion resistance, is required. In the present work, NiCrAlY and Ni-20Cr metallic coatings were deposited on an iron-based superalloy by a shrouded plasma spray process. The coatings were characterized by scanning electron microscopy, optical microscopy, microhardness testing, and x-ray diffractometry. Erosion studies were conducted using an air-jet erosion test rig at a velocity of 40ms−1 and impingement angles of 30 and 90deg. Scanning electron microscopy was used to analyze the eroded surfaces. 3D surface roughness profiles of the eroded samples were taken using a Veeco Optical Profilometer. NiCrAlY coatings had slightly lower average porosity and lower microhardness as compared to Ni-20Cr coatings. The observed erosion rate of the NiCrAlY coatings, however was lower than that of the Ni-20Cr coatings at both 30 and 90deg impingement angles. Ni-20Cr coating had shown higher erosion rate at 90deg impingement angle than that at 30deg, whereas the effect of impingement angle on the erosion rate is negligible for plasma sprayed NiCrAlY coating. The higher bond strength of NiCrAlY coating might be one of the major contributing factors for lower erosion rate of NiCrAlY coating as compared to Ni-20Cr coating under the tested conditions. Erosion mechanisms of plasma sprayed coatings are discussed.

Influences of Fe2O3 Doping on the Crystallization of SiO2-Al2O3-MgO-K2O-ZrO2-F Glass-Ceramics

2009 ◽  
Vol 79-82 ◽  
pp. 1503-1506 ◽  
Author(s):  
Qing Bo Tian ◽  
Li Na Xu ◽  
Li Yang ◽  
Yan Sheng Yin
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Elevated Temperatures ◽  
Glass Ceramics ◽  
X Ray Diffraction ◽  
Crystallization Peak ◽  
X Ray ◽  
Microstructural Morphology ◽  
Microscopy Techniques ◽  
Scanning Electron

The influences of Fe2O3 doping on crystallization characteristics and microstructural morphology in the SiO2-Al2O3-MgO-K2O-ZrO2-F glass were investigated by using differential scanning calorimeter, X-ray diffraction and scanning electron microscopy techniques. The results indicate that the addtions of Fe2O3 shift the crystallization peaks to higher temperatures and the crystallization peaks increases in magnitude and the gap values between two crystallization peak temperatures boarden with the increment of Fe2O3 contents.The star-shaped crystals of cordietite by dendritic-manner growths are homogeneously precipitated in the rusidual glass. The mica phases, which are precipitated at interdendritic cordietite phases and formed the plate shapes at the elevated temperatures. The mica crystals grow at the expense of cordietite phases and finally form the composites of mica/cordietite uniformly distributed.

Bioactivity of Plasma-Sprayed Diopside Coating In Vitro

2005 ◽  
Vol 288-289 ◽  
pp. 319-322 ◽  
Author(s):  
Wei Chang Xue ◽  
Chuan Xian Ding ◽  
Cong Cao ◽  
Yuqi Dong
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Cell Proliferation ◽  
Cross Section ◽  
Body Fluid ◽  
Human Osteoblast ◽  
Suitable Candidate ◽  
Plasma Sprayed ◽  
Scanning Electron

A new bioceramic coating based on diopside was prepared by plasma spraying. The surface and cross-section microstructure of the coating were examined by scanning electron microscopy. The thermal expansion coefficient of the diopside coating measured by a dilatometer adapted to that of titanium alloy. The bond strength of the coating was about 32.5 MPa, which is higher than that of HA coatings used in orthopedics and dentistry. The bioactivity of diopside coating was evaluated in vitro. After 15 days soaking in simulated body fluid, an apatite layer was formed on the surface of the coating. The cytocompatibility was investigated by studying the behaviour of human osteoblast cultured directly onto the surface of the coating. MTT assay was performed to assess the influence of the coating on cell proliferation. The morphologies of the cell were observed by SEM after incubation for 1 and 7 days. The results obtained indicated that plasma sprayed diopside coating may be a suitable candidate for bone and dental implant.

scholarly journals Study of gypsum composites with fine solid aggregates at elevated temperatures

2021 ◽  
Vol 28 (1) ◽  
pp. 237-248
Author(s):  
Magdaléna Doleželová ◽  
Lenka Scheinherrová ◽  
Alena Vimmrová
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Elevated Temperatures ◽  
Silica Sand ◽  
X Ray Diffraction ◽  
Volume Changes ◽  
X Ray ◽  
Final Volume ◽  
Scanning Electron ◽  
Better Than

Abstract The structure and behaviour of two gypsum composites after exposition to elevated temperatures were investigated. The silica sand and fine basalt aggregate were used as solid fillers. The changes in structure and composition at temperatures from 50 to 1,000°C were investigated by scanning electron microscopy and X-ray diffraction together with the size and strength of the samples and their pore size distribution. The structure of gypsum matrix changed significantly at 1,000°C in both composites, while the aggregate particles were not changed. It was found that even if the silica sand is considered as less suitable filler at high temperatures because of its volume changes, the gypsum with sand performed better than gypsum with basalt at the highest temperatures, because the shrinkage of the gypsum matrix was compensated by the increase in the volume of aggregate. The final volume change at 1,000°C was 3.5% in composite with silica sand and 6.8% in composite with basalt. The residual compressive strength of both composites was about 9.4%. No cracks appeared in the samples and no spalling was observed.

scholarly journals Deposition of Gold (III) from Hydrochloric Acid Solutions on Carbon Nanotubes under Hydrothermal Conditions

2019 ◽  
pp. 494-502 ◽  
Author(s):  
Roman V. Borisov ◽  
Oleg V. Belousov ◽  
Anatoliy M. Zhizhaev
Keyword(s):  
Electron Microscopy ◽  
Carbon Nanotubes ◽  
Scanning Electron Microscopy ◽  
Hydrochloric Acid ◽  
Elevated Temperatures ◽  
Acid Solutions ◽  
Hydrothermal Conditions ◽  
Gold Particles ◽  
Hydrochloric Acid Solutions ◽  
Scanning Electron

The paper deals with the recovery of gold (III) from hydrochloric acid solutions on carbon based nanotube material at elevated temperatures under autoclave conditions. It is established that the quantitative recovery of gold (III) from hydrochloric acid solution upon its contact with carbon material occurs at a temperature of 170 °C for 240 minutes. The morphological features of metallic gold particles are studies by scanning electron microscopy

Absolute Coating Porosity Measurement Using Image Analysis

1998 ◽  
Author(s):  
K. Mailhot ◽  
F. Gitzhofer ◽  
M.I. Boulos
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Image Analysis ◽  
Functionally Graded ◽  
Scattered Electron ◽  
Graded Materials ◽  
Composite Substrate ◽  
Plasma Sprayed ◽  
Electron Imaging ◽  
Scanning Electron

Abstract This paper describes the procedure that has been developed for absolute porosity measurement using Image Analysis (IA). Because of the crumbly nature of the composite substrate, it was not possible to proceed with standard method. The IA conducted on Optical Microscopy did not show enough contrast between pores and other features to be automated. The IA conducted on Scanning Electron Microscopy (SEM) with back scattered electron imaging gives enough contrast for automatic threshold determination. The SEM magnification is a parameter to be considered because it filters the information. Three frames at 500X magnification are enough for measuring the porosity of homogeneous supersonic induction plasma sprayed 018 mm samples (thickness 50-100 µm). The established calibration almost shows a 1 to 1 ratio for the image analysis as measured porosity versus the Archimedean porosity. Application of this absolute porosity determination by IA can be found in the Functionally Graded Materials (FGM) which composition is not constant over the layer thickness.

Analysis of Retrieved Hydroxyapatite Coated Orthopaedic Implants

1998 ◽  
Author(s):  
K.A. Gross ◽  
B. Ben-Nissan ◽  
W.R. Walsh ◽  
E. Swarts
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Revision Surgery ◽  
Interface Strength ◽  
Adhesive Failure ◽  
X Ray Diffraction ◽  
X Ray ◽  
Plasma Sprayed ◽  
Implanted Devices ◽  
Scanning Electron

Abstract Hydroxyapatite (HAp) coatings are used to improve the adhesion of bone onto implanted devices. This approach increases the integrity and hence the lifetime of the implant. Several orthopaedic appliances (HAp coated and macrotextured) were recovered from patients after revision surgery. The implants were cleaned and sterilised in ethanol or formaldehyde before being photographed and sectioned for analysis. X-ray diffraction indicated that the remaining coating was of high crystallinity. Micro textured areas such as ribbings and fenestrations subjected the coating to different modes of stress which has affected the coating. Adhesive failure was evident on implants attributed to dissolution of the amorphous phase at the interface. Observation of the microstructure with scanning electron microscopy showed that coating degradation begins at the surface where the coating is resorbed and continues along the substrate-coating interface thereby compromising interface strength. The microstructure and the dissolution of retrieved implants are discussed in relation to the general coating features in plasma sprayed HAp coatings.

The Formed Mechanism of Pores in Plasma Sprayed Nanostructured Al2O3/TiO2 Coatings

2013 ◽  
Vol 423-426 ◽  
pp. 139-144 ◽  
Author(s):  
Wei Qin Wu ◽  
Zhen Yi Wei
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Plasma Spraying ◽  
Plasma Spray ◽  
Spray Coating ◽  
Lamellar Morphology ◽  
Feed Stock ◽  
Plasma Sprayed ◽  
Different Sources ◽  
Scanning Electron

Pores are common defects in the coating formed via plasma spraying. In order to investigate the formed mechanism of pores in plasma sprayed nanostructured Al2O3-TiO2 coatings, the microstructure of the feed stock, splat and coating were characterized by means of scanning electron microscopy (SEM). The coating shows a typical lamellar morphology, which contains fully melted (FM) zone and partly melted (PM) zone.The pores in different places of the coating were generated from different sources. The shapes and the size of the pores are also different. Keywords: plasma spray, coating, pores, formed mechanism

Effect of welding conditions on erosive wear of hard-faced Co-based alloy layer

2018 ◽  
Vol 232 (11) ◽  
pp. 1377-1389 ◽  
Author(s):  
Begori Venkatesh ◽  
Bharti Malvi ◽  
Manish Roy ◽  
Pallab Sarkar
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Solid Particle ◽  
Steel Substrate ◽  
Erosive Wear ◽  
Ductile Material ◽  
Material Loss ◽  
Air Jet ◽  
The Impact ◽  
Scanning Electron

Degradation of materials due to the impact of solid particle is a major material wastage process. Modifying the surface of materials can be considered to be a potential method of improving the resistance to erosion. In the present days, weld hard-facing is a popular surface modification process. Engineering industries are opting for hard-facing because of its low capital cost, low operational cost, and operational simplicity. In the context of erosion-resistant hard materials, a series of Co-based alloys that can be deposited by hard-facing is one of the most suitable materials. The present analysis has been carried out to evaluate the influence of processing conditions of hard-faced Co-based alloyed layer on solid particle erosion response at ambient temperature. These layers were deposited on mild steel substrate by weld hard-facing. The mechanical properties and microstructural features of these coatings were evaluated by means of X-ray diffraction technique, optical microscopy, scanning electron microscopy, and microhardness tester. Erosion rate was measured using an air jet erosion test rig. The eroded surface morphology and the transverse section of eroded surfaces were viewed using scanning electron microscopy. The results showed that hard-facing improves erosion resistance of the substrate. The erosion responses of most of the coatings were ductile. Material loss from hard-faced coating was by formation of lips followed by their fracture which initiated in the interdendritic regions.

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