MICROSTRUCTURE AND MICROHARDNESS EVALUATION FOR NiCrAlY MATERIALS MANUFACTURED BY SPARK PLASMA SINTERING AND PLASMA SPRAYING

NiCrAlY deposited by different thermal spraying methods is commonly used as the bond coat material in thermal barrier coatings (TBCs). In the present study, two experimental coatings were deposited by hybrid water stabilized plasma (WSP-H) and radio frequency inductively coupled plasma (RF-ICP) using the same feedstock powder. Spark plasma sintering (SPS) was used to manufacture a compact NiCrAlY from the same feedstock powder as a reference material. Microstructure, internal oxidation, phase characterization and quantification of the mechanical behaviour in terms of microhardness were studied. The investigations clearly showed microstructural and mechanical differences between the NiCrAlY samples manufactured by different plasma technologies. The results confirmed that SPS and RF-ICP provide dense structures with no oxides due to the fabrication under protective atmosphere and similar mechanical properties. Thus, RF-ICP may be used for deposition of very dense coatings with microstructure and hardness comparable to compacted materials prepared by SPS.

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Influence of Carbon Diffusion and the Presence of Oxygen on the Microstructure of Molybdenum Powders Densified by SPS

Metals ◽

10.3390/met10070948 ◽

2020 ◽

Vol 10 (7) ◽

pp. 948

Author(s):

Mathias Moser ◽

Sylvain Lorand ◽

Florian Bussiere ◽

Frédéric Demoisson ◽

Hervé Couque ◽

...

Keyword(s):

Grain Growth ◽

Spark Plasma Sintering ◽

Inductively Coupled Plasma ◽

Sintering Temperature ◽

Carbon Diffusion ◽

Inductively Coupled ◽

Molybdenum Carbides ◽

Plasma Sintering ◽

Fine Microstructure ◽

Spark Plasma

Due to molybdenum’s Body-Centered Cubic (BCC) crystalline structure, its ductile–brittle transition temperature is sensitive to shaping, purity and microstructure. Dense molybdenum parts are usually shaped by the powder metallurgy process. The aim of this work concerns the spark plasma sintering of high-purity powders prepared by inductively coupled plasma. The influence of carbon diffusion and its interaction with oxygen on the density (i.e., the densification stage) and on the microstructure (i.e., the grain growth stage) during spark plasma sintering was investigated. The formation of carbide is usually expected for a sintering temperature above 1500 °C leading to grain growth (e.g., more than 10 times larger than the initial powder grain size after sintering at 1900 °C for 10 min). The brittleness was also affected by the segregation of molybdenum carbides at the grain boundaries (i.e., intergranular brittle fracture). Consequently, to reduce the sintering temperature to below 1500 °C, mechanically activated powders were used. From these milled powders, a dense molybdenum disc (60 mm in diameter and 10 mm in thickness) sintered at 1450 °C under a pressure of 70 MPa for 30 min was obtained. It is composed of a fine microstructure without carbide and oxide, its ductility is close to 13% with a maximum resistance of 550 MPa.

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Fe-Si-Al Alloys Prepared by a Spark Plasma Sintering Technique

Materials Science Forum ◽

10.4028/www.scientific.net/msf.827.300 ◽

2015 ◽

Vol 827 ◽

pp. 300-305 ◽

Cited By ~ 1

Author(s):

Toto Sudiro ◽

Kemas Ahmad Zaini Thosin ◽

Didik Aryanto ◽

Agus Sukarto Wismogroho ◽

Kazuya Kurokawa

Keyword(s):

Spark Plasma Sintering ◽

Al Alloys ◽

Sintering Behavior ◽

X Ray Diffraction ◽

Sem Images ◽

X Ray ◽

Oxide Inclusions ◽

Plasma Sintering ◽

Spark Plasma ◽

Phase Characterization

Fe-Si alloys with various concentration of Al (0, 1, 3 and 5 % by mass) were synthesized by a spark plasma sintering technique. The specimens were prepared in an evacuated chamber of less than 4 Pa and under compressive stress of 40 MPa. During spark discharge, the heating rate was fixed at 10°C/min. After the SPS process was completed, the specimen surfaces were ground with silicon carbide papers. The metallographic characterization was performed by mean of X-ray diffraction (XRD) and scanning electron microscope (SEM) equipped with energy dispersive X-ray (EDX) spectroscopy. According to sintering curves, all samples seem to have a similar sintering behavior. The densification of specimens was completed in the temperature range of about 1020-1050°C. Microstructure and phase characterization revealed that the alloys were mainly composed of FeSi2 and FeSi phases containing oxide inclusions. The SEM images indicated that the fraction of FeSi phase and oxide inclusions appears to decrease with increase in Al concentration in the Fe-Si alloy.

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Sintering and kinetic mechanism of Si3N4-SiC micro-nano composite by spark plasma sintering

Functional Materials Letters ◽

10.1142/s1793604717500035 ◽

2017 ◽

Vol 10 (02) ◽

pp. 1750003

Author(s):

Mohammad Khajelakzay ◽

Saeed Reza Bakhshi ◽

Gholam Hossein Borhani ◽

Mazaher Ramazani

Keyword(s):

Spark Plasma Sintering ◽

Kinetic Mechanism ◽

X Ray Diffraction ◽

Nano Composite ◽

Plasma Sintering ◽

Spark Plasma ◽

Sic Composites ◽

Boundary Reaction ◽

Phase Characterization

Si3N4–SiC composites were fabricated by spark plasma sintering at 1700[Formula: see text]C for 480 S with MgSiN2 and Y2O3 as additives. The morphology and phase characterization of the composites were characterized using scanning electron microscopy (SEM) and X-ray diffraction (XRD). The values of [Formula: see text] parameter indicate that the grain boundary reaction is the rate controller at 1500[Formula: see text]C and diffusion becomes the controlling step at 1550[Formula: see text]C. The nanohardness and Young’s modulus attained the maximum value of 18.5 and 316[Formula: see text]GPa, respectively.

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Spark Plasma Sintering of LiFePO4: AC Field Suppressing Lithium Migration

Materials ◽

10.3390/ma14112826 ◽

2021 ◽

Vol 14 (11) ◽

pp. 2826

Author(s):

Nan Luo ◽

Yong Lin ◽

Jian Guo ◽

Emanuele Quattrocchi ◽

Huaijiu Deng ◽

...

Keyword(s):

Spark Plasma Sintering ◽

Photoelectron Spectroscopy ◽

Inductively Coupled Plasma ◽

High Performance ◽

Optical Emission ◽

Ion Migration ◽

Plasma Sintering ◽

Spark Plasma ◽

Li Ion ◽

Ac Field

Our work proposes a comparison between Spark Plasma Sintering of LiFePO4 carried out using an Alternating Current (AC) and Direct Current (DC). It quantifies the Li-ion migration using DC, and it validates such hypothesis using impedance spectroscopy, X-ray photoelectron spectroscopy and inductively coupled plasma optical emission spectroscopy. The use of an AC field seems effective to inhibit undesired Li-ion migration and achieve high ionic conductivity as high as 4.5 × 10−3 S/cm, which exceeds by one order of magnitude samples processed under a DC field. These results anticipate the possibility of fabricating a high-performance all-solid-state Li-ion battery by preventing undesired Li loss during SPS processing.

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