巻号一覧
77 巻, 6 号
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特集「地球環境の負荷低減をめざす高温耐食材料と耐食コーティング」
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川原 雄三2013 年 77 巻 6 号 p. 199
発行日: 2013年
公開日: 2013/06/01
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解説論文
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林 重成2013 年 77 巻 6 号 p. 200-209
発行日: 2013年
公開日: 2013/06/01
ジャーナル フリーEffect of various factors on the metastable to stable phase transformation behavior of a thermally grown oxide scale of Al2O3 was reviewed and discussed on the basis of the results obtained from our recent studies. In this paper, among the factors affecting this phase transformation, particular attention has focused on the effect of Fe in order to understand the different phase transformation behavior of Al2O3 scale formed on different alloy systems in different oxidation environments. In order to explore the effect of Fe on the phase transformation, the oxidation behavior of various Al2O3 forming Fe-based model alloys was systematically investigated. The development of different oxide scales on different alloys during a high-temperature oxidation, including the initial transient stage of oxidation followed by isothermal oxidation in different oxidation atmospheres, was examined by in-situ X-ray diffraction by means of the Synchrotron radiation. Fe was found to accelerate the phase transformation to α-Al2O3. This effect can be considered to be due to an initial formation of Fe2O3, which is an isomorphous crystal structure with α-Al2O3. Further contributing factor of Fe on the transformation can be a doping of Fe3+ ion, which formed during an initial transient oxidation stage, in the Al2O3 scale. The oxidation atmospheres are considered to indirectly affect the phase transformation by changing in the formation behavior of Fe2O3 and (Al, Fe)2O3 solid solution during an initial transient oxidation stage.
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西山 佳孝, 土井 教史, 森口 晃治2013 年 77 巻 6 号 p. 210-217
発行日: 2013年
公開日: 2013/06/01
ジャーナル フリーWe present a joint experimental and theoretical study on metal dusting phenomena in Ni binary alloys containing group-14 and 15 elements in the periodic series. Laboratory metal dusting test of several Ni binary alloys was conducted in a simulated syngas atmosphere consisting of CO, H2, CO2, and H2O at 923 K for 100 h. The Ni alloys containing the group-14 and 15 elements exhibited excellent metal dusting resistance. This behavior is reasonably interpreted by the Blyholder mechanism and the electron filling concept in the p-d hybridization states for the associated alloys. Furthermore, surface segregation of the group-14 and 15 elements was analyzed by ARXPS on the Ni alloys after exposing at 923 K in a vacuum. The behavior of those segregation was quantitatively associated with the non-dissociative adsorption.
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福本 倫久, 力石 健, 杉田 聖英, 原 基2013 年 77 巻 6 号 p. 218-224
発行日: 2013年
公開日: 2013/06/01
ジャーナル フリーThe formation of coating layer consisting of a Ni aluminide containing Hf on a Ni substrate was tried by the electrodeposition of Hf and Al. The cyclic oxidation resistance for the Ni covered with the coating was then evaluated. Hf and Al were deposited by molten salt electrolysis. For the sample treated with the Hf deposition, followed by the Al deposition at 1023 K, the Ni2Al3 layer and Al3Hf layer were formed in that order from the substrate. On the other hand, for the sample treated with the Hf deposition, followed by the Al deposition at 1173 K, the NiAl layer containing Hf was formed. Further, when electrodeposition time of Hf was changed, the amount of Hf in NiAl layer was changed. The cyclic oxidation test showed that for the untreated sample, the sample with Al depositions and the sample coated with Ni2Al3/Al3Hf layer, the mass reduction due to exfoliation of a scale took place. However, for the sample coated NiAl layer containing of Hf, the mass reduction was not observed. For this sample after the cyclic oxidation test, a scale consisting of α-Al2O3 adhering to the substrate was formed. Consequently, it was found that a cyclic oxidation resistance of the sample was improved by coating with the NiAl layer containing Hf.
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礒本 良則, 河西 徹, 川原 雄三2013 年 77 巻 6 号 p. 225-230
発行日: 2013年
公開日: 2013/06/01
ジャーナル フリーSelf-fluxing alloys are useful for component materials as coatings in energy conservation systems and power plants due to high resistance of high temperature corrosion and erosion. However, the mechanical properties of the self-fluxing alloy coatings at high temperatures have not been precisely investigated. In order to develop highly durable coatings and apply to practical services, we focused on measurements of hardness and fracture toughness for the self-fluxing alloys at room and high temperatures. Spherical particle impact tests were conducted for three types of self-fluxing alloys to obtain dynamic hardness and dynamic fracture toughness. Three point bending tests were additionally performed. As results, the hardness and fracture toughness of the three self-fluxing alloys were found to be almost constant at room and high temperatures up to 873 K, although a little decrease in fracture toughness occurred at 1073 K. The fracture toughness related to elastic modulus and F/C1.5 (F: load, C: crack length), and have a tendency of increasing with increase in Brinell hardness.
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礒本 良則, 河西 徹, 川原 雄三, 吉原 美知子2013 年 77 巻 6 号 p. 231-236
発行日: 2013年
公開日: 2013/06/01
ジャーナル フリーSelf-fluxing alloy coatings are useful for components of industrial equipments in sand erosion or wear environments as well as high temperature corrosive and oxidation environments. However, the erosion characteristics by solid particle for the self-fluxing alloys have not been adequately investigated, then needed in order to develop highly durable coating alloys and apply to practical erosive services. Erosion tests at room temperature were conducted for three types of self-fluxing alloys to obtain impact angle dependence of erosion rate or normalized erosion using a sand blast type erosion test rig. We focused on hardness, fracture toughness and fracture energy of self-fluxing alloys at room and high temperatures. The relationships between erosion characteristics and these mechanical properties were discussed and erosion rate of the self-fluxing alloys at high temperature was extrapolated. The exponent numbers which show impact angle dependence of sand erosion, and erosion rates at an impact angle of 90 degrees were well related to micro Vickers hardness and roughly related both to Brinell hardness and to fracture energy. It was found that the erosion rates for the self-fluxing alloys at high temperatures up to 873 K could be estimated as almost equal to that at room temperature, as well as equivalent mechanical properties at temperatures up to 873 K.
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論文
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安田 弘行, 丸山 武紀2013 年 77 巻 6 号 p. 237-244
発行日: 2013年
公開日: 2013/06/01
ジャーナル フリーThe pseudoelastic behavior of Fe-Ga polycrystals was examined focusing on the effects of Ga concentration, heat treatment and deformation temperature. Fe-Ga polycrystals solutionized at 800℃ exhibited pseudoelasticity at room temperature based on reversible motion of 1/4〈111〉 superpartial dislocations dragging an antiphase boundary (APB) in the D03 superlattice structure. In particular, at and above 25 at%Ga, paired 1/4〈111〉 superpartials dragging the next-nearest-neighbor APB were found to play an important role in the pseudoelasticity. The amount of strain recovery at room temperature was highest at 25 at%Ga. Moreover, heat treatment strongly influenced the pseudoelastic behavior of Fe-Ga alloys. For instance, the L12 and ω-like phases precipitating at higher Ga concentrations led to a decrease in strain recovery since the precipitates suppressed the reversible motion of 1/4〈111〉 superpartials. On the other hand, pseudoelasticity based on twinning and untwinning of 2.2T-type pseudo-twins appeared at low temperatures, especially at −180℃. The energy of {211} pseudo-twins formed in the Fe-Ga alloys was so high that the twins tended to disappear during unloading resulting in the pseudoelasticity. However, the amount of strain recovery decreased if pseudoelasticities based on dislocation motion and twinning concurrently took place between −150℃ and −50℃.
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阿部 拓平, 佐藤 菜花, 福本 倫久, 原 基2013 年 77 巻 6 号 p. 245-252
発行日: 2013年
公開日: 2013/06/01
ジャーナル フリーA coating of Ni aluminide/Ni or TiAl3 bilayer on a TiAl substrate was formed by the electrodeposition of Ni with a different deposition time and the electrodeposition of Al using a molten salt electrolyte. The electrodeposition of Al was carried out using a potentiostatic polarization method in molten NaCl-KCl-AlF3 at 1023 K. By this electrodeposition treatment, surface layers mainly consisting of Ni2Al3 and intermediate layers consisting of Ni or TiAl3 were formed. The cyclic oxidation resistance of these specimens was examined in air at 1323 K. As a result, for the specimens with a thick Ni layer as the intermediate layer, an exfoliation of the coating was observed and the mass reduction due to spalling of an oxide scale was observed. On the other hand, for the specimens with TiAl3 or thin Ni layer as the intermediate layer, the exfoliation of the coating was not observed and a high-cyclic oxidation resistance was observed. For the specimens showing a high-cyclic oxidation resistance after the cyclic oxidation test, a surface layer consisting of NiAl with Al2O3 scale and an intermediate layer consisting of TiAl2 containing a small amount of Ni were formed. For the specimens showing exfoliation of the coating, the formation of the intermediate layer consisting of TiAl2 was not observed.
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