Tunthawiroon, Phacharaphon

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Tunthawiroon, Phacharaphon
Alternative Name
TUNTHAWIROON, Phacharaphon
Tunthawiroon, P.
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Email
phacharaphon.tu@kmitl.ac.th

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    Characterization of oxide films on wrought Co–Cr–Mo–xSi alloys exposed to high-temperature oxidation
    (2021-10-01)
    Tunthawiroon, Phacharaphon
    ;
    Kitiwan, Mettaya
    ;
    Srirussamee, Kasama
    ;
    Li, Yunping
    ;
    Yamanaka, Kenta
    Co-based alloys are currently being used in a wide range of high temperature applications owing to their high resistance to oxidation and corrosion. However, their oxidation-induced degradation could still occur during the long-term exposure to high temperature. Thus, the continuous development of oxidation-resistant Co-based alloys is of crucial importance. In this research, the influence of Si addition on the oxidation behavior of Co–Cr–Mo–xSi alloys under the isothermal oxidation treatment at 700 °C in air was investigated. The Si concentration (x) was varied from 0.1 to 5.0 wt.%. Surface morphologies and chemical compositions of the oxide films formed were analyzed by using SEM-EDS and XPS. The chemical compositions obtained from the surface analysis revealed that Si has played a role in the stabilization of Cr oxides on the surface of Co–Cr–Mo–xSi alloys. With increasing Si concentration, Co-oxide formation on the alloy surface was suppressed by the presence of Cr-oxide due to the selective oxidation of Cr atoms. Furthermore, SiO<inf>2</inf> was both found along the grain boundaries and interfaces between the outmost oxide layer and matrix. It was also found that the oxide thickness was reduced with increasing Si concentration. This was a result of the formation of stable Cr-oxide and SiO<inf>2</inf> sub-layer that became a barrier inhibiting the inward and outward diffusion of O and Cr.
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    Evidence for chromium, cobalt and molybdenum volatilisations during high temperature oxidation of Co-27Cr-6Mo Alloy
    (2022-07-01)
    Wongpromrat, Patthranit
    ;
    Galerie, Alain
    ;
    Thublaor, Thammaporn
    ;
    Chandra-ambhorn, Walairat
    ;
    Ponpo, Phisan
    A Co-27Cr-6Mo alloy was oxidised in pure O<inf>2</inf> between 800 and 1000 °C for durations up to 96 h. The flow rate was varied between 2 and 5 cm.s<sup>–1</sup>. In these conditions, volatilisations of chromium, cobalt and molybdenum were observed. The chromium volatilisation values were in good agreement with calculations assuming (CrO<inf>3</inf>)g volatilisation limited by diffusion in the gas boundary layer. On the contrary, the measured flux of evaporated Co was higher than the calculated Co volatilisation flux from the metallic Co. The theoretical relation between the solid Co particle size and its vapour pressure was suggested to help explaining such difference.
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    Xps analysis of oxide formed on the surface of co-28cr-6mo-1si alloy oxidized at 550 ºc
    (2020-01-01)
    Tunthawiroon, Phacharaphon
    ;
    Kitiwan, Mettaya
    ;
    Wongpromrat, Patthranit
    ;
    Chiba, Akihiko
    This work investigated the influence of oxidation durations on the formation of oxide on the surface of wrought Co-28Cr-6Mo-1Si alloy. The iso-thermal oxidation was individually performed in air at 550ºC for 4, 12 and 24 h. For comparison, the surface of the non-oxidized Co-28Cr-6Mo-1Si alloy was concurrently examined. The chemical compositions of the non-oxidized and oxidized alloys were principally analyzed via X-ray photoelectron spectroscopy (XPS). The XPS results revealed that the surface of the non-oxidized alloy enriched in Cr-oxide. After oxidation treatment, the Co-oxide, existing as Co<sup>2+</sup> state was observed coexisting with two Cr-oxide states, Cr<sup>3+</sup> and Cr<sup>4+</sup>. The low concentrations of Mo<sup>6+</sup> were also observed on the oxidized alloy surface. With the increase in oxidation durations, the Co-oxide was suppressed by Cr-oxide. The XPS depth profile analysis indicated that the thickness of the oxide film increased with increasing the oxidation duration.
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    A study on wettability and formation of intermetallic phase between Co–Cr–Mo alloy and Sn-Solder used as a potential under bump metallization for flip-chip packages
    (2020-10-01)
    Kyaw, Tin Tin
    ;
    Tunthawiroon, Phacharaphon
    ;
    Kanlayasiri, Kannachai
    ;
    Yamanaka, Kenta
    ;
    Chiba, Akihiko
    The wettability and formation of intermetallic compounds (IMCs) formed between a Co–Cr–Mo-based alloy and Sn-solder metal were investigated using the reflow soldering method. Soldering was conducted in an electric furnace in separate experiments at temperatures of 533, 553, 573, 623, and 673 K for 600 s. The morphology of the intermetallic layer formed at the Co–Cr–Mo-based/Sn-solder interface was characterized by scanning electron microscopy (SEM). The chemical composition and phase of the formed intermetallic layer were analyzed by electron probe microscopic analysis (EPMA) and X-ray diffraction analysis. Wettability analysis indicated that the soldering temperature influenced the wettability. With increasing soldering temperatures, the spreading factor increased, whereas the contact angle decreased. The intermetallic layers were found in triples in the intermediate zone between the solidified Sn-solder and the Co–Cr–Mo-based substrate. The thickness of the intermetallic layers increased in proportion with increasing soldering temperature. The EPMA analysis indicated only two IMCs formed at the interface of the joint at all of the investigated soldering temperatures, although three interfacial layers were observed by SEM analysis. The Sn-richer phase, Co(Cr,Mo)Sn<inf>2</inf>, formed adjacent to the Sn-solder matrix, whereas the Co(Cr,Mo)Sn was found near the Co–Cr–Mo-based substrate. The nanoindentation measurement revealed that the formed Co(Cr,Mo)Sn<inf>2</inf> and Co(Cr,Mo)Sn IMCs possessed lower hardness values compared to the Sn–Cu intermetallic systems.
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    Corrosion behavior of a Co-Cr-Mo-Si alloy in pure Al and Al-Si melt
    (2023-01-01)
    Yamanaka, Kenta
    ;
    Mori, Manami
    ;
    Yoshida, Kazuo
    ;
    Tunthawiroon, Phacharaphon
    ;
    Chiba, Akihiko
    Metallic phase change materials (MPCMs) are attracting considerable attention for their application in thermal energy storage. Al-Si alloys are considered potential MPCMs; however, to develop storage systems/modules, it is crucial to fabricate corrosion-resistant materials for MPCMs. In this study, the corrosion behavior of Co-28Cr-6Mo-1.5Si (wt%) alloy was examined via immersion tests in commercial Al-Si alloy (ADC12) melt at 700°C for 10 h. The results were compared to those obtained for pure Al. Substrate thickness loss measurements revealed that the liquid metal corrosion was more severe in the Al-Si melt than that in pure Al, suggesting an increased reactivity due to Si addition. Interfacial analysis elucidated a direct reaction between the alloy substrate and molten Al in both cases. Furthermore, the formation of oxides such as Al2O3 and SiO2 did not contribute to corrosion resistance.