Faculty Profiles - OTSUBO Fumitaka

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Microstructure and Mechanical Properties of YAG Laser Welded Spheroidal Graphite Cast Iron Reviewed

Otsubo Fumitaka, Fukumatsu Kiyotaka

Journal of Japan Foundry Engineering Society ( Japan Foundry Engineering Society ) 95 ( 11 ) 615 - 621 2023.11

Authorship：Lead author,　Corresponding author Language：Japanese Publishing type：Research paper (scientific journal)

Cast iron welding improves the performance of joints using welding rods for cast iron. However, such rods are more than twice as expensive as those for mild steel. The authors found that when spheroidal graphite cast iron is melted and rapidly solidified, graphite nodules aggregate and move to the surface. If the graphite nodules in the fusion zone move to the surface, the carbon concentration may reduce, thereby suppressing the generation of ledeburite. In this study, by irradiating with YAG laser, I-type butt-welded joints were fabricated using L materials (with an average nodule diameter of 52 μm) specimens without groove width. Ferrite and pearlite matrices joints were undermatch joints. Applying PWHT (Post Weld Heat Treatment) restored the joint strength to more than 90 % that of the base metal. The impact value for the as-welded joint dropped to less than 15 % of that for the base metal. However, it could be recovered up to about 40 % of that for the base metal by PWHT. Ferrite matrix joints after PWHT exhibited similar level impact values as the as-welded pearlite matrix joints. Moreover, the surface of spheroidal graphite cast iron with different numbers and size of graphite nodules was irradiated with YAG laser. As a result, at irradiation feed rates above 100 cm/min L, materials specimen exhibited a much lower hardness in the fusion zone than S materials (with an average nodule diameter of 27 μm) specimen. The graphite nodules in the fusion zone moved to the surface during rapid melting by laser irradiation. In the S materials specimen studied, more ledeburite, martensite and retained austenite formed near the fusion boundary than with the L materials specimen.

DOI： 10.11279/jfes.95.615

Structures and hardness of materials formed by melting and liquid diffusion of Mg alloy substrate with pure Al surface+ Reviewed International journal

Fumitaka Otsubo

Materials Transactions ( The Japan Institute of Metals and Materials ) 61 ( 8 ) 1657 - 1662 2020.08

Authorship：Lead author,　Corresponding author Language：English Publishing type：Research paper (scientific journal)

In this study, pure Al powder was compression molded on the surface of flame-retardant Mg alloy plate, and integration of pure Al and Mg alloy was attempted by melting and solidification in air. In order to integrate different materials by liquid diffusion of metal elements, the structure, composition phase and hardness of the formed integrated materials were investigated.It was found that heating the specimens for 180 s results in melting and liquid diffusion between Al and Mg. When heated and melted with pure Al down and Mg alloy up (Type B), shrinkage cavity was formed on the former Mg alloy side of the former Al/former Mg alloy interface. When heated at 450 s, the specimen was composed of Al–Mg system stable phases of Al3Mg2 and Al12Mg17, and Al–Mg system metastable phases of Al0.37Mg0.63 and Al0.1Mg0.9. In Type A with pure Al up and Mg alloy down and Type B, stable phases of Al3Mg2 and Al12Mg17 were formed on the former Al side. The constituent phase of the former Mg alloy side was composed of metastable phases of Al0.37Mg0.63 and Al0.1Mg0.9, but the structure morphologies of Type A and B differed near the surface of the former Mg alloy side, and the primary phase was Al0.37Mg0.63 and Al0.1Mg0.9 respectively. The final solidification phase consisted of eutectic phases of Al0.37Mg0.63 and Al0.1Mg0.9. The hardness on the former Al side was about 250 HV, and the hardness on the former Mg alloy side had decreased. Type B was evaluated to be lower than Type A. This Paper was Originally Published in Japanese in J. JFS 92 (2020) 69–74.

DOI： 10.2320/matertrans.F-M2020830

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TEM analysis of whiskers formation over tin-plated films "jointly worked" Reviewed International journal

Fumitaka Otsubo, Hidenori Era, Yutaka Tsuru, Shigeru Hirano

Materials Chemistry and Physics 251 (2020) 122985 2020.04

Structures and Hardness of Materials Formed by Melting and Liquid Diffusion of Mg Alloy Substrate with Pure Al Surface Reviewed

Otsubo Fumitaka

Journal of Japan Foundry Engineering Society ( Japan Foundry Engineering Society ) 92 ( 2 ) 69 - 74 2020.01

Authorship：Lead author,　Corresponding author Language：Japanese Publishing type：Research paper (scientific journal)

In this study, pure Al powder was compression-molded on the surface of a flame-retardant Mg alloy plate, and integration of pure Al and Mg alloy was attempted by melting and solidification in air. In order to integrate different materials by liquid diffusion of metal elements, the structure, composition phase and hardness of the formed integrated materials were investigated. It was found that heating the specimens for 180s results in melting and liquid diffusion between Al and Mg. When heated and melted with pure Al down and Mg alloy up (Type B), shrinkage cavity was formed on the former Mg alloy side of the former Al/former Mg alloy interface. When heated at 450s, the specimen was composed of Al-Mg system stable phases of Al3Mg2 and Al12Mg17, and Al-Mg system metastable phases of Al0.37Mg0.63 and Al0.1Mg0.9. In Type A with pure Al up and Mg alloy down and Type B, stable phases of Al3Mg2 and Al12Mg17 were formed on the former Al side. The constituent phase of the former Mg alloy side was composed of metastable phases of Al0.37Mg0.63 and Al0.1Mg0.9, but the structure morphologies of Type A and B differed near the surface of the former Mg alloy side, and the primary phase was Al0.37Mg0.63 and Al0.1Mg0.9 respectively. The final solidification phase consisted of eutectic phases of Al0.37Mg0.63 and Al0.1Mg0.9. The hardness on the former Al side was about 250HV, and the hardness on the former Mg alloy side had decreased. Type B was evaluated to be lower than Type A.

DOI： 10.11279/jfes.92.69

Other Link： https://ci.nii.ac.jp/naid/130007804110

Cladding of Al Layer onto Mild Steel Substrate Using Al Powder and Its Structure and Properties Reviewed

59 ( 10 ) 1585 - 1590 2018.10

Columnar Ferrite Structure in Cast Iron Formed by Decarburization of White Cast Iron Reviewed

59 ( 8 ) 1326 - 1332 2018.08

Columnar Ferrite Structure in Cast Iron Formed by Decarburization of White Cast Iron Reviewed

Otsubo Fumitaka, Matsuki Kousuke, Era Hidenori, Kuroki Hidenori

Journal of Japan Foundry Engineering Society ( Japan Foundry Engineering Society ) 90 ( 2 ) 61 - 67 2018.01

Authorship：Lead author,　Corresponding author Language：Japanese Publishing type：Research paper (scientific journal)

Cast iron objects such as axes and other artifacts excavated from ancient sites generally have a layered structure with columnar ferrite on the outside, changing to pearlite and ledeburite with increasing depth, together with a minor fraction of dispersed graphite; this structure is the result of the heat treatment used in the decarburization process. The formation of the columnar ferrite structure has previously been explained by assuming that cast iron was produced using a metal mold and then decarburized. In this study, in order to clarify this issue, decarburization experiments were performed on white cast iron. Part of a white cast iron block, containing the surface that had been in contact with the mold during casting, in addition to a cut surface, was heated to 1273K, held at that temperature for 96h, and then slowly cooled to 873K at 67K/h (for 6h). It was found that columnar ferrite crystals grew in the direction perpendicular to the surface regardless of the solidification direction. The ferrite structure did not have a uniform crystal orientation, similar to the case for partially decarburized ancient cast iron. Therefore, this clarified that the issue was a misunderstanding without materials scientific grounds. In addition, when white cast iron was decarburized at 1123K for 48h and cooled to 873K at 42K/h, the overall thickness of the decarburized layers was close to that for ancient artifacts. Therefore, it is likely that in ancient times, the same type of cast iron and heat treatment conditions were used.

DOI： 10.11279/jfes.90.61

Other Link： https://ci.nii.ac.jp/naid/130006407089

鋳鉄中に生成した球状黒鉛の構造と物性 Invited

坪田俊樹，大坪文隆，佐野秀明，吉元昭二，梅谷拓郎，吉澤徳子

炭素材料科学の進展 ( 日本学術振興会炭素材料第117委員会 ) 2018.11

溶射による表面改質技術 Invited

大坪文隆

月刊トライボロジー ( （株）新樹社 ) 32 ( 8 ) 43 - 45 2018.08

白鋳鉄の脱炭により形成された鋳鉄の柱状フェライト組織 Reviewed

大坪文隆、松木康祐、恵良秀則、黒木英憲

鋳造工学 90 ( 2 ) 61 - 67 2018.02

Mg合金基板とその表面に成形したAl 圧粉層の溶融凝固材の組織と特性 Reviewed

大坪文隆, 大森百合香, 佛木大亮

鋳造工学全国講演大会講演概要集 ( 公益社団法人日本鋳造工学会 ) 172 ( 0 ) 31 - 31 2018.01

Columnar ferrite structure in cast iron formed by decarburization of white cast iron+ Reviewed

Otsubo F., Matsuki K., Era H., Kuroki H.

Materials Transactions 59 ( 8 ) 1326 - 1332 2018.01

Cladding of al layer onto mild steel substrate using al powder and its structure and properties Reviewed

Otsubo F., Era H.

Materials Transactions 59 ( 10 ) 1585 - 1590 2018.01

高周波誘導加熱による球状黒鉛鋳鉄の表面焼入れ性（共著） Reviewed

徳永辰也、若菜凌、濱口主税、浦濱大地、岩川風、福永修大、丸山栄三郎、大坪文隆、恵良秀則

溶射 54 ( 1 ) 8 - 11 2017.01

Al粉末を用いた軟鋼基材へのAl層のクラッド加工およびその組織と特性 Reviewed

大坪文隆, 恵良秀則

塑性と加工 58 ( 678 ) 582 - 586 2017.01

Authorship：Lead author Language：Japanese Publishing type：Research paper (scientific journal)

Pure aluminum powder with grain sizes of 45 to 10μm preformed on aluminum (A1050) and mild steel (SPCC)<tt> </tt>substrates were rolled to form cladding materials at room temperature in air. The partial rolling reduction of the Al cladding layer was smaller than that of the A1050 substrate in an Al powder/A1050 cladding sheet. In contrast, the partial rolling reduction of the Al cladding layer was larger than that of the SPCC substrate in an Al powder/SPCC cladding sheet. The difference in the partial rolling reduction of the cladding layers and SPCC substrates became smaller with increasing total rolling reduction of the Al powder/SPCC cladding sheets. The shear adhesion strength of the Al powder/SPCC cladding sheet was about 40MPa, which decreased to about 10MPa after heat treatment at 773K for 3.6ks. The intermetallic compounds were formed between the cladding layer and the substrate after heat treatment at 773K for 3.6ks. Also, the cladding layer showed excellent oxidation resistance compared with cast iron after heat treatment at 1073K for 36ks in air, though light oxidation occurred in specimens after heat treatment at 773K for 36ks in air.

DOI： 10.9773/sosei.58.582

Other Link： https://ci.nii.ac.jp/naid/130005858702

Change in Eutectic Structure of AC4C Aluminum Alloy Castings Obtained by Solidification after Electric Current Melting by Use of Spot Welding Machine Reviewed

Journal of Japan Foundry Engineering Society 87 ( 10 ) 695 - 701 2015.10

Change in Eutectic Structure of AC4C Aluminum Alloy Castings Obtained by Solidification after Electric Current Melting by Use of Spot Welding Machine Reviewed

Otsubo Fumitaka, Matsunaga Yuuki, Era Hidenori

Journal of Japan Foundry Engineering Society ( Japan Foundry Engineering Society ) 87 ( 10 ) 695 - 701 2015.01

Authorship：Lead author Language：Japanese Publishing type：Research paper (scientific journal)

The structure and hardness of aluminum alloy (JIS : AC4C) obtained by solidification after electric current melting by use of a spot welding machine were investigated focusing on structure formation through the loss of homogeneity and its properties. The molten area of the sample increased with increasing heat input and the columnar sample melted with further heat input. The center and outside areas of the samples exhibited a granular α-Al structure and fine eutectic structure, respectively. The fine structure with α-Al and eutectic phases of α-Al and Si formed in the whole area of the sample under a maximum heat input of 400J. The hardness of the outside area was generally higher than that of the center area, except when the heat input was maximum. It is found that the change in hardness with heat input was caused by the change in the area of the eutectic phase of α-Al and Si. The hardness of the outside area of the sample solidified under an appropriate heat input, e. g., 270J was twice as high as that of the as-cast ingot. Furthermore, the outside area of the appropriately solidified sample further hardened with the T5-heat treatment and the hardness was 50% higher compared to the center area. Thus the outside of the appropriately solidified sample, achieved by suitable heat input, markedly enhanced its hardness, bringing about the potential for wear resistant improvement.

DOI： 10.11279/jfes.87.695

Other Link： https://ci.nii.ac.jp/naid/130005529567

Solidification Structure of Al-Cu and Sn-Cu-Sb Alloys Obtained by Casting through Induction Stirring Using Permanent Magnet Reviewed

55 ( 5 ) 806 - 812 2014.05

Spheroidal Graphite Formation in Ni-C Alloy

B4-1 2013.12

Thermal Conduction Simulation and Structure Formation of SGI During Heating by Running Induction Coil

B5-3 2013.12

Reproduction of matallographic structure of ancient cast iron

H-07 - H-07 2013.10

Microstructure and Heat Transfer Simulation of SGI Press Forming Dies by Induction Hardening

36 - 38 2013.09

Formation of Spheroidal Graphite in Nickel Alloy

79 - 81 2013.09

Measurement of Viscosity of Non-combustible Molten Magnesiumu Alloy "jointly worked" Reviewed

Journal of Japan Foundry Engineering Society 83 ( 10 ) 569 - 573 2011.10

Crystallographic Observation for Au/Au Bond Interface by Ultrasonic Bonding Reviewed

Journal of Japan Institute of Elactronics Packaging 12 ( 4 ) 307 - 312 2009.07

Crystallographic Observation for Au/Au Bond Interface by Ultrasonic Bonding Reviewed

SOGAWA Mitsuomi, OTSUBO Fumitaka, YAMAGUCHI Tomiko, NISHIO Kazumasa, ERA Hidenori

Journal of The Japan Institute of Electronics Packaging ( Japan Institute of Electronics Packaging ) 12 ( 4 ) 307 - 312 2009.07

Language：English Publishing type：Research paper (scientific journal)

A crystallography study and observation of microstructure were carried out on the joint of an Au ball and Au electrode formed using two modes of ultrasonic bonding which show differences under the life test. A non-bonded joint was seen on the samples using SEM observation. Also, it was found that the length of bonding of the LP sample, which was bonded using low ultrasonic output, was short compared with that of the HP sample, which was bonded using high ultrasonic output. From an analysis of the IPF image obtained using EBSD, the interface of the joint in the LP sample apparently retained the crystal orientation of the interface before bonding. However, {001} in the HP sample, the crystal grain formed parallel to the bonded plane in the newly formed large area without obvious interface from the joint. It was concluded from this that the crystal grain having the same axis as the Au ball formed in the Au electrode though the orientation was not obvious from SEM and TEM observation.

DOI： 10.5104/jiep.12.307

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Sealing Oxides of Thermal sprayed Alumina Coating and Its Formation Process Reviewed

OTSUBO Fumitaka, KOZASA Nobuhiro, SHINOZAKI Nobuya, ERA Hidenori, KISHITAKE Katsuhiko

QUARTERLY JOURNAL OF THE JAPAN WELDING SOCIETY ( JAPAN WELDING SOCIETY ) 26 ( 2 ) 195 - 201 2008.12

Language：English Publishing type：Research paper (scientific journal)

The sealing of pores by a veined oxide in a thermal sprayed alumina coating with some kinds of metal particle was investigated by heating in air. Also, the oxide grew from the metallic substrate into an artificial pore in the alumina block was observed after heating in air. The sealing of pores arose by the spinel oxide in the alumina coating containing Ni, Co or NiCrAlY particles after heating at 1173K for 100h in air. The oxide grew from Ni substrate into the artificial pore in alumina block after heating at 1273K for 100h in air. The oxide formed from the Ni substrate in the pore consisted of NiO (core) and NiAl2O4 spinel oxides. Also, the NiAl2O4 spinel formed from the top of the grown oxide on the surface of the pore. The spinel oxide preferentially forms on the surface of the pore and the primary oxide of the metal occupies the remaining space in the pore.

DOI： 10.2207/qjjws.26.195

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Sealing Oxides of Thermal Sprayed Alumina Coating and Its Formation Process Reviewed

Quarterly Journal of the Japan Welding Society 26 ( 2 ) 195 - 201 2008.04

Formation of Ni3Al in Sprayed Coating of Ni-Al Composite Powder by Heat-Treatment Reviewed

Journal of Japan Thermal Spray Society 44 ( 3 ) 83 - 87 2007.07

Super Elongation of High Purity Al-Si Alloy Castings Reviewed

T. Ogawa,K. Kimura,Y. Koga,F. Otsubo,H. Era

Proceedings of The 16th International Microscopy Congress 3 '1676 - 1676 2006.09

Residual Stress Distribution in Thermally Sprayed Self-Fluxing Alloy Coatings Reviewed

Journal of Japan Thermal Spray Society 43 ( 2 ) 42 - 46 2006.04

固有ひずみ法による球状黒鉛鋳鉄溶接部の残留応力分布測定 Reviewed

原田浩次，大坪文隆，寺崎俊夫，岸武勝彦

鋳造工学 78 ( 1 ) 9 - 13 2006.01

Residual Stress Distribution in Thermally Sprayed Self-Fluxing Alloy Coatings Reviewed

F.Otsubo,K.Kishitake,T.Terasaki

Materials Transactions 46 ( 11 ) 2473 - 2477 2005.11

Corrosion Resistance of Fe-16%Cr-30%Mo-(C,B,P) Amorphous Coatings Sprayed by HVOF and APS Processes Reviewed

F.Otsubo,K.Kishitake

Materials Transactions 46 ( 1 ) 80 - 83 2005.01

Corrosion resistance of Fe-16%Cr-30%Mo-(C,B,P) amorphous coatings sprayed by HVOF and APS processes Reviewed

Otsubo F., Kishitake K.

Materials Transactions 46 ( 1 ) 80 - 83 2005.01

Corrosion resistance of Fe-Cr-Mo-(C,B,P) amorphous coatings thermal sprayed by HVOF and APS processes Reviewed

Otsubo F., Shimoda A., Era H., Kishitake K.

Proceedings of the International Thermal Spray Conference 439 - 441 2004.12

Language：English Publishing type：Research paper (international conference proceedings)

Two kinds of Fe-16Cr-30Mo-(C,B,P) alloy powders of different composition were thermal sprayed onto mild steel using HVOF and APS processes. Perfect amorphous coating was formed by HVOF and APS processes in both powders. The corrosion potential of the amorphous coatings sprayed by HVOF process was higher and the passive current density was lower than that of the amorphous coatings sprayed by APS process in 1N HCl solution. The coatings of perfect amorphous phase were little corroded after one week immersion tests and the corrosion rates of the amorphous coatings showed a fairly less value of 0.03 mm/y compared with Inconel 625 plate in 5N HCl solution at room temperature.

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ブラスト処理したフェライト基地球状黒鉛鋳鉄の曲げ特性 Reviewed

大坪文隆,岸武勝彦,寺崎俊夫

鋳造工学 76 ( 6 ) 469 - 472 2004.06

Characterization of Blasted Austenitic Stainless Steel and Its Corrosion Resistance Reviewed

F.Otsubo,K.Kishitake,T.Akiyama,T.Terasaki

Journal of Thermal Spray Technology 12 ( 4 ) 555 - 559 2003.12

Characterization of blasted austenitic stainless steel and its corrosion resistance Reviewed

Otsubo F., Kishitake K., Akiyama T., Terasaki T.

Journal of Thermal Spray Technology 12 ( 4 ) 555 - 559 2003.12

Language：English Publishing type：Research paper (scientific journal)

It is known that the corrosion resistance of stainless steel is deteriorated by blasting, but the reason for this deterioration is not clear. A blasted austenitic stainless steel plate (JIS-SUS304) has been characterized with comparison to the scraped and non-blasted specimens. The surface roughness of the blasted specimen is larger than that of materials finished with #180 paper. A martensite phase is formed in the surface layer of both blasted and scraped specimens. Compressive residual stress is generated in the blasted specimen and the maximum residual stress is formed at 50-100 μm from the surface. The corrosion potentials of the blasted specimen and subsequently solution treated specimen are lower than that of the non-blasted specimen. The passivation current densities of the blasted specimens are higher those of the non-blasted specimen. The blasted specimen and the subsequently solution treated specimen exhibit rust in 5% sodium chloride (NaCl) solution, while the non-blasted specimen and ground specimen do not rust in the solution. It is concluded that the deterioration of corrosion resistance of austenitic stainless steel through blasting is caused by the roughed morphology of the surface.

DOI： 10.1361/105996303772082305

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固有ひずみ法による球状黒鉛鋳鉄溶接部の残留応力分布測定

原田浩次,大坪文隆,岸武勝彦,寺崎俊夫

日本鋳造工学会鋳鉄材料研究部会研究報告92 110 - 114 2003.11

ブラスト処理によるオーステナイトステンレス鋼の耐食性劣化 Reviewed

大坪文隆,秋山哲也,岸武勝彦,寺崎俊夫

溶射 39 ( 3 ) '108－11 - -108－112 2002.07

高速フレーム溶射したFe-Cr-Mo-８P-2C 合金非晶質溶射皮膜の耐塩酸性 Reviewed

大坪文隆,恵良秀則,岸武勝彦

溶接学会論文集 19 ( 1 ) '54－5 - -54－59 2001.02

Resistance to Hydrochloric Acid Solution of Fe-Cr-Mo-8P-2C Amorphous Coatings Sprayed by HVOF Process. Reviewed

OTSUBO Fumitaka, ERA Hidenori, KISHITAKE Katsuhiko

QUARTERLY JOURNAL OF THE JAPAN WELDING SOCIETY ( JAPAN WELDING SOCIETY ) 19 ( 1 ) 54 - 59 2001.02

Language：English Publishing type：Research paper (scientific journal)

Three kinds of Fe-8P-2C alloy powders containing 10 mass%Cr (10Cr), 20 mass%Cr (20Cr) and 10 mass%Cr-10 mass%Mo (10Mo), respectively, were thermally sprayed by a high velocity oxy-fuel (HVOF) process. The as-sprayed coatings of the 10Cr and 20Cr alloys are a mixture of an amorphous phase and a small quantity of crystalline phases, while as-sprayed coating of the 10Mo alloy is composed of only an amorphous phase. The anodic polarization curves of the coatings of the 10Cr and 20Cr alloys exhibited an activation-passivation transition in 1NHCl solution. On the other hand, the coating of the 10Mo allo, showed no active state and the lowest current density among the alloy coatings in the anodic polarization curve. The passive state of the coating of the 10Mo alloy was stable compared with the other coatings. The coating of the 10Mo alloy als, underwent no corrosion in 1NHCl solution at 0.5 and 1.0 V (vs. SCE), whereas Inconel 600 alloy plate was attacked remarkably.

DOI： 10.2207/qjjws.19.54

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Properties of Cr3C2-NiCr Cermet Coating Sprayed by High Power Plasma and High Velocity Oxy-Fuel Processes Reviewed

F.Otsubo,H.Era,T.Uchida,K.Kishitake

Journal of Thermal Spray Technology 9 ( 4 ) 499 - 504 2000.12

Formation of Amorphous Fe-Cr-Mo-8P-2C Coatings by the High Velocity Oxy-Fuel Process Reviewed

F.Otsubo,H.Era,K.Kishitake

Journal of Thermal Spray Technology 9 ( 4 ) 494 - 498 2000.12

Properties of Cr<inf>3</inf>C<inf>2</inf>-NiCr cermet coating sprayed by high power plasma and high velocity oxy-fuel processes Reviewed

Otsubo F., Era H., Uchida T., Kishitake K.

Journal of Thermal Spray Technology 9 ( 4 ) 499 - 504 2000.12

Language：English Publishing type：Research paper (scientific journal)

The structure, hardness, and shear adhesion strength have been investigated for Cr3C2-NiCr cermet coatings sprayed onto a mild steel substrate by 200 kW high power plasma spraying (HPS) and high velocity oxy-fuel (HVOF) processes. Amorphous and supersaturated nickel phases form in both as-sprayed coatings. The hardness of the HVOF coating is higher than that of the HPS coating, because the HVOF coating contains more nonmelted Cr3C2 carbide particles. On heat treating at 873 K, the amorphous phase decomposes and the supersaturated nickel phase precipitates Cr3C2 carbides so that the hardness increases in the HPS coating. The hardness measured under a great load exhibits lower values compared with that measured with a small load because of cracks generated from the indentation. The ratio of the hardnesses measured with different loads can be regarded as an index indicating the coating ductility. The ductility of the HVOF coating is higher than that of the HPS coating. Adhesion strength of the HVOF coating was high compared with the HPS coating. The adhesion of the coatings is enhanced by heat treating at 1073 K, and that of the HVOF coating is over 350 MPa.

DOI： 10.1361/105996300770349719

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Formation of amorphous Fe-Cr-Mo-8P-2C coatings by the high velocity oxy-fuel process Reviewed

Otsubo F., Era H., Kishitake K.

Journal of Thermal Spray Technology 9 ( 4 ) 494 - 498 2000.12

Language：English Publishing type：Research paper (scientific journal)

Alloy powders of Fe-10%Cr-8%P-2%C(10Cr), Fe-20%Cr-8%P-2%C(20Cr), and Fe-10%Cr-10%Mo-8%P-2%C(10Mo) compositions (in mass%) were sprayed by the high velocity oxy-fuel (HVOF) process under different conditions. The as-sprayed coatings of 10Mo alloy were composed of only an amorphous phase under all the spray conditions, while the as-sprayed coatings of the 10Cr and 20Cr alloys consisted of an amorphous phase with a small amount of crystalline material. The volume fraction of the crystalline material increased slightly with the rise of the flame temperature. The hardnesses of the as-sprayed coatings of the 10Cr and 20Cr alloys were 600 to 700 DPN, respectively, while the 10Mo coating composed of an amorphous phase revealed 560 DPN. The corrosion resistance of the as-sprayed coating of the 10Mo alloy was the best among three amorphous coatings and also superior to the nickel-base self-fluxing alloy and SUS316L stainless steel coatings in 1N H2SO4 and 1N HCl solutions.

DOI： 10.1361/105996300770349700

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Interface Reaction between Nickel-Base Self-Fluxing Alloy Coating and Steel Substrate Reviewed

F.Otsubo,H.Era,K.Kishitake

Journal of Thermal Spray Technology 9 ( 2 ) 259 - 263 2000.06

Interface reaction between nickel-base self-fluxing alloy coating and steel substrate Reviewed

Otsubo F., E. E., Kishitake K.

Journal of Thermal Spray Technology 9 ( 2 ) 259 - 263 2000.06

Language：English Publishing type：Research paper (scientific journal)

The interface reaction between a nickel-base, self-fluxing alloy coating and a steel substrate has been investigated to examine the formation of 'pores,' which are observed along the interface of used boiler tubes. It was found that lumpy precipitates form along the interface instead of pores after heating at high temperatures and that the precipitates are of Fe2B boride. The adhesion strength of the coating is not decreased by the formation of Fe2B precipitates along the interface because of the increase of the adhesion due to interdiffusion.

DOI： 10.1361/105996300770350014

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Structure and Phases in Nickel-Base Self-Fluxing Alloy Coating Containing High Chromium and Boron Reviewed

F.Otsubo,H.Era,K.Kishitake

Journal of Thermal Spray Technology 9 ( 1 ) 2000.03

Structure and phases in nickel-base self-fluxing alloy coating containing high chromium and boron Reviewed

Otsubo F., Era H., Kishitake K.

Journal of Thermal Spray Technology 9 ( 1 ) 107 - 113 2000.03

Language：English Publishing type：Research paper (scientific journal)

The structure of a nickel-base, self-fluxing alloy coating, containing chromium and boron thermal sprayed and fused, was investigated by x-ray diffraction (XRD), scanning electron microscopy (SEM), electron probe microanalysis (EPMA), and transmission electron microscopy (TEM). A lumpy M6C carbide, a rodlike M3B2 boride of tetragonal structure, a rodlike M7C3 carbide of hexagonal structure, and a Ni-Ni3B eutectic phase formed in the coating after fusing. Metals of M6C, M3B2, and M7C3 phases are composed of chromium, molybdenum, and nickel; chromium and molybdenum; and mainly chromium, respectively. The nickel phase in the coating has the L12 type superlattice structure.

DOI： 10.1361/105996300770350131

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ニッケル基自溶合金溶射皮膜の組織と生成相 Reviewed

岸武勝彦,恵良秀則,大坪文隆

溶接学会論文集 18 ( 1 ) 126 - 132 2000.02

Structure and Phases in Nickel-Base Self Fluxing Alloy Coating. Reviewed

KISHITAKE Katsuhiko, ERA Hidenori, OTSUBO Fumitaka

QUARTERLY JOURNAL OF THE JAPAN WELDING SOCIETY ( JAPAN WELDING SOCIETY ) 18 ( 1 ) 126 - 132 2000.02

Language：English Publishing type：Research paper (scientific journal)

The structure and constituents in two types of nickel-base self fluxing alloy coatings thermal sprayed and subsequently fused were precisely investigated by use of X-ray diffraction analysis, electron probe microanalysis, scanning electron microscopy and transmission electron microscopy. JIS-MSFNi1 alloy coating was composed of primary nickel solid solution and Ni3B phase between primary nickel grains with a small amount of Ni-Ni3B eutectic. In case of JIS-MSFNi4 alloy coating, lumpy crystals and two kinds of rod-like crystals appeared in addition to Ni-Ni3B eutectic. It was found that the lumpy crystal is M6C carbide containing chromium, molybdenum and nickel. The rod-like crystals are M3B2 boride of tetragonal structure and M7C3 carbide of hexagonal structure. Metal constitution of M3B2 are chromium and molybdenum and M7C3 contains mainly chromium. The nickel phase in the Ni-Ni3B eutectic of MSFNi4 alloy coating has the superlattice structure.

DOI： 10.2207/qjjws.18.126

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Improvement of adhesion strength and formation of veined structure in alumina coating Reviewed

Era H., Otsubo F., Kishitake K.

Proceedings of the International Thermal Spray Conference 1 711 - 716 1998.12

Language：English Publishing type：Research paper (international conference proceedings)

Alumina coatings plasma-sprayed on alumina substrate with metallic bond coating (50Ni-50Cr) and on metal (Ni) substrate have been investigated in terms of adhesion strength and a veined structure formed in alumina coating. The veined structure is formed to heal up cracks and pores in sprayed alumina and substrate alumina after heat-treatment in air. The veined structure consists of oxides of NiAl2O4 (spinel-type) and NiO (NaCl-type). This indicates that the metallic elements in the bond coating or the metallic substrate diffuse along the cracks and pores in alumina and react with alumina. The alumina coating with veined structure shows high strength due to the mechanical anchoring of veined oxide and chemical bonding.

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High corrosion resistant iron-based amorphous coatings obtained by thermal spraying Reviewed

Otsubo F., Era H., Kishitake K., Matsumoto H.

Proceedings of the International Thermal Spray Conference 1 659 - 664 1998.12

Language：English Publishing type：Research paper (international conference proceedings)

Fe-Cr(-Mo)-metaloids alloy coatings were thermal sprayed by different processes of LPPS, HVOF and HPS. The as-sprayed coating by LPPS is perfectly amorphous and coatings by other processes contain partly crystalline phases. The amorphous phases crystallize at 773 K or more and shows a high hardness of about 1000 to 1400 DPN just after crystallization. The anodic polarization curves of the coatings shift from active to passive state in 1N H 2SO 4 and 1N HCl solutions. The coatings obtained by LPPS indicate the lowest active and passive current densities and possess the best corrosion resistance. The corrosion resistance of the coatings obtained by other processes are better than a SUS316L stainless steel coating. The LPPS coating of Fe-Cr-C-P alloy is not attacked on immersion test in 6% FeCl 3·6H 2O + 0.05N HCl solution at corrosion potential, while large pit corrosion is developed in a SUS316L stainless steel sheet.