High Temperature Corrosion Behavior of Si-Containing Alloys in the Gas Phase of Air-(Na2SO4+25.7mass%NaCl)

The objective of this study is to develop an excellent corrosion resistant alloy for high temperature coating applications. The Si-containing alloys consisting of CoNiCrAlY and CrSi2 alloys with varying Si and Ni content respectively were prepared by spark plasma sintering (SPS) technique. The corrosion behavior of these alloys was investigated in the gas phase of air-(Na2SO4+25.7mass%NaCl) at elevated temperatures of 923, 1073 and 1273K. The results showed that CoNiCrAlY alloy with 30mass% Si content and CrSi2 alloy with 10mass% Ni content were the most effective materials for application in the gas phase of air-(Na2SO4+25.7mass%NaCl) due to the formation of protective Al2O3/SiO2 and SiO2 scale, respectively. Therefore, it is realized that CoNiCrAlY-30mass% Si and CrSi2-10mass% Si coating are very effective for improving of high temperature corrosion resistance of STBA21 steel.

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High Temperature Corrosion Behavior of Si-Containing Alloys in the Liquid Phase of Na2SO4 25.7 Mass% NaCl

Defect and Diffusion Forum ◽

10.4028/www.scientific.net/ddf.323-325.353 ◽

2012 ◽

Vol 323-325 ◽

pp. 353-358 ◽

Cited By ~ 3

Author(s):

Toto Sudiro ◽

Tomonori Sano ◽

Shoji Kyo ◽

Osamu Ishibashi ◽

Masaharu Nakamori ◽

...

Keyword(s):

High Temperature ◽

Liquid Phase ◽

Corrosion Behavior ◽

High Temperature Corrosion ◽

Corrosion Mechanism ◽

Plasma Sintering ◽

Ni Addition ◽

Spark Plasma ◽

Si Content ◽

Conicraly Alloy

The high temperature corrosion behavior of Si-containing alloys consisting of Cr-Si-Ni and CoNiCrAlY-Si alloys fabricated by spark plasma sintering technique was investigated in the liquid phase of Na2SO4 + 25.7 mass% NaCl at temperatures ranging from 923-1273 K. The purpose of this study is to develop excellent corrosion resistant alloys for coating applications. Our experimental results show the CrSi2 alloy with 10 mass% Ni content and the CoNiCrAlY alloy with 30 mass% Si content are the most promising materials for applications in this atmosphere. This is due to the formation of a protective SiO2 and Al2O3/SiO2 scale, respectively. The formation of a dense and continuous oxide layer composed and/or consisted of SiO2 plays a significant role in hindering the inward diffusion of chlorine and sulfur to the alloys substrate. Particularly, the corrosion mechanism of Cr-Si-Ni alloys and the influence of Ni addition on the corrosion resistance of CrSi2 alloy are discussed in the present paper.

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Phase Analyses of a TtPt Alloy Synthesized by Spark Plasma Sintering

Materials Science Forum ◽

10.4028/www.scientific.net/msf.675-677.1143 ◽

2011 ◽

Vol 675-677 ◽

pp. 1143-1146

Author(s):

Hilda Kundai Chikwanda ◽

Yoko Yamabe-Mitarai ◽

Silethelwe Chikosha

Keyword(s):

High Temperature ◽

Spark Plasma Sintering ◽

Room Temperature ◽

Elevated Temperatures ◽

Mechanically Alloyed ◽

Plasma Sintering ◽

High Temperature Xrd ◽

Pt Alloy ◽

Spark Plasma ◽

Sintered Alloys

A Ti-50at%Pt alloy synthesized using the spark plasma sintering (SPS) technique has been characterized for phases’ identification. TiPt alloys have potential use as high temperature shape memory alloys(HTSMAs). Test specimens were prepared at SPS temperature of 1300°C. Sintering pressure and time were varied. The microstructural features of the specimens were investigated using scanning electron microscopy (SEM) and X-ray diffraction (XRD). The electron microscope used was equipped with an EDS detector, that, together with the XRD, were used for both the identification and analyses of the phases in the starting materials and the sintered alloys. High temperature XRD (800 -1300°C) as well as ambient temperature XRD analyses were done on the starting mechanically alloyed powders. All the samples tested at elevated temperatures were subsequently tested at room temperature after cooling. XRD analyses of the sintered samples were all done at room temperature. Analyses of the XRD results revealed new distinct phases from a temperature of 1000°C. A comparison of the room temperature XRD results for alloy powders and that of the sintered alloys was made. The following phases have been identified and studied TiPt B2, TiPt B19, Pt3Ti, Ti3Pt and Pt5Ti3. SPS pressure and sintering time did not show much effect on the phases detected. The alloy composition was found to be very inhomogeneous.

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Fabrication and Characterization of Quinary High Entropy-Ultra-High Temperature Diborides

Ceramics ◽

10.3390/ceramics4020010 ◽

2021 ◽

Vol 4 (2) ◽

pp. 108-120

Author(s):

Simone Barbarossa ◽

Roberto Orrù ◽

Valeria Cannillo ◽

Antonio Iacomini ◽

Sebastiano Garroni ◽

...

Keyword(s):

High Temperature ◽

Single Phase ◽

Nominal Composition ◽

High Entropy ◽

Chemical Complexity ◽

Alternative Processing ◽

Plasma Sintering ◽

High Temperature Synthesis ◽

Spark Plasma

Due to their inherent chemical complexity and their refractory nature, the obtainment of highly dense and single-phase high entropy (HE) diborides represents a very hard target to achieve. In this framework, homogeneous (Hf0.2Nb0.2Ta0.2Mo0.2Ti0.2)B2, (Hf0.2Zr0.2Ta0.2Mo0.2Ti0.2)B2, and (Hf0.2Zr0.2Nb0.2Mo0.2Ti0.2)B2 ceramics with high relative densities (97.4, 96.5, and 98.2%, respectively) were successfully produced by spark plasma sintering (SPS) using powders prepared by self-propagating high-temperature synthesis (SHS). Although the latter technique did not lead to the complete conversion of initial precursors into the prescribed HE phases, such a goal was fully reached after SPS (1950 °C/20 min/20 MPa). The three HE products showed similar and, in some cases, even better mechanical properties compared to ceramics with the same nominal composition attained using alternative processing methods. Superior Vickers hardness and elastic modulus values were found for the (Hf0.2Nb0.2Ta0.2Mo0.2Ti0.2)B2 and the (Hf0.2Zr0.2Ta0.2Mo0.2Ti0.2)B2 systems, i.e., 28.1 GPa/538.5 GPa and 28.08 GPa/498.1 GPa, respectively, in spite of the correspondingly higher residual porosities (1.2 and 2.2 vol.%, respectively). In contrast, the third ceramic, not containing tantalum, displayed lower values of these two properties (25.1 GPa/404.5 GPa). However, the corresponding fracture toughness (8.84 MPa m1/2) was relatively higher. This fact can be likely ascribed to the smaller residual porosity (0.3 vol.%) of the sintered material.

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