Takaishi, Japan
Takaishi, Japan

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Sudiro T.,Hokkaido University | Sano T.,Hokkaido University | Sano T.,Mitsubishi Group | Kyo S.,Kansai Electric Power Co. | And 3 more authors.
Materials Transactions | Year: 2012

In this study, an attempt has been made to improve the resistance of CrSi 2 alloy toward high temperature corrosion and promote the formation of a continuous and slow-growing SiO 2 scale on the alloy surface. For this purpose, spark plasma sintering was used to fabricate the CrSi 2 alloys containing various amounts of CoNiCrAlY. The sintered alloys were then corroded isothermally in an airNa 2SO 4NaCl gas atmosphere at three different temperatures of 923 and 1073K for up to 720 ks and at 1273K for 72 ks. XRD, SEM and SEM-EDS were utilized to examine the alloy structures and compositions before and after the high temperature corrosion test. The influence of CoNiCrAlY addition on the high temperature corrosion behavior of the CrSi 2 alloy was clarified. © 2012 The Japan Institute of Metals.


Sudiro T.,Hokkaido University | Sano T.,Hokkaido University | Sano T.,Mitsubishi Group | Kyo S.,Kansai Electric Power Co. | And 3 more authors.
Defect and Diffusion Forum | Year: 2012

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 Na 2SO 4 + 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 CrSi 2 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 SiO 2 and Al 2O 3/SiO 2 scale, respectively. The formation of a dense and continuous oxide layer composed and/or consisted of SiO 2 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 CrSi 2 alloy are discussed in the present paper. © (2012) Trans Tech Publications.


Sudiro T.,Hokkaido University | Sano T.,Hokkaido University | Sano T.,Mitsubishi Group | Kyo S.,Kansai Electric Power Co. | And 3 more authors.
Oxidation of Metals | Year: 2013

The present paper is designed to provide a summary of our study on the high temperature corrosion of Al2O3, SiO2 and Al2O3-SiO2 forming alloys in the gas phase and liquid phase of Na2SO4-NaCl system by comparing their corrosion resistance at 1000 C. The obtained results show that the alumina-forming alloy experiences severe internal corrosion in the gas phase compared to in the liquid phase due to oxide cracking. This results in an increase in the inward diffusion and/or penetration of constituents of the salts and oxygen to form internal Al-oxide and Cr-sulfides. In the liquid phase, however, the formation of yttrium sulfide beneath a continuous double oxides layer of Al5Y3O12 and Al2O 3 may be related to the high affinity of yttrium for sulfur. On the other hand, it is apparent from the cross-sectional observations that a SiO 2 and Al2O3-SiO2 forming alloys form a continuous and dense oxides layer, and demonstrate a high resistance against internal oxidation and corrosion in both corrosive environments. © 2013 Springer Science+Business Media New York.


Sudiro T.,Hokkaido University | Sano T.,Hokkaido University | Kyo S.,Kansai Electric Power Co. | Ishibashi O.,Osaka Fuji Corporation | And 2 more authors.
Materials Transactions | Year: 2011

The addition of Si to CoNiCrAlY was considered in order to develop corrosion resistant alloys for coating applications. The high temperature corrosion behavior of spark plasma sintered CoNiCrAlY alloys of 0, 10, 20, and 30 mass% Si content was investigated in an air(Na 2SO 4+25.7 mass%NaCl) gas atmosphere at elevated temperatures of 923, 1073, and 1273 K. The results showed that CoNiCrAlY-Si alloys formed mainly an Al 2O 3 or Al 2O 3/SiO 2 scale, depending on the alloy composition and the temperature. The addition of 30% Si significantly improved the high-temperature corrosion resistance of CoNiCrAlY alloy in an air-(Na 2SO 4+25.7 mass%NaCl) gas atmosphere at these temperatures. The high temperature corrosion behavior of CoNiCrAlY-Si alloys was discussed in the present paper. ©2011 The Japan Institute of Metals.


Sudiro T.,Hokkaido University | Sano T.,Hokkaido University | Yamauchi A.,Hokkaido University | Kyo S.,Kansai Electric Power Co. | And 3 more authors.
Materials Science Forum | Year: 2011

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 CrSi 2 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-(Na 2SO 4+25.7mass%NaCl) at elevated temperatures of 923, 1073 and 1273K. The results showed that CoNiCrAlY alloy with 30mass% Si content and CrSi 2 alloy with 10mass% Ni content were the most effective materials for application in the gas phase of air-(Na 2SO 4+25.7mass%NaCl) due to the formation of protective Al 2O 3/SiO 2 and SiO 2 scale, respectively. Therefore, it is realized that CoNiCrAlY-30mass% Si and CrSi 2-10mass% Si coating are very effective for improving of high temperature corrosion resistance of STBA21 steel. © (2011) Trans Tech Publications.


Sudiro T.,Hokkaido University | Kyo S.,Kansai Electric Power Co. | Ishibashi O.,Osaka Fuji Corporation | Nakamori M.,High Temperature Corrosion and Protection Technosearch Co. | Kurokawa K.,Hokkaido University
Materials Transactions | Year: 2012

As an extension of our previous work to develop a high corrosion resistant alloy for coating applications, a fundamental study of high temperature corrosion behavior of spark plasma sintered CoNiCrAlY alloys with varying Si content as 0, 10, 20 and 30% by mass has been performed. The high temperature corrosion tests were carried out in the liquid phase (melted salt) of Na 2SO 4-NaCl at elevated temperatures of 923 and 1073K for up to 720 ks and at 1273K for 72 ks. Our results demonstrate that the CoNiCrAlY alloy suffers from internal corrosion attack at these temperatures. On the other hand, the addition of 30 mass% Si leads to beneficial effects not only in the suppression of the formation of internal corrosion products, but also in reducing the growth of external oxide layer. In this paper, the high temperature corrosion behavior of CoNiCrAlY-Si alloys and the influences of Si addition on the corrosion resistance are intensely discussed. © 2012 The Japan Institute of Metals.


Motoyasu G.,Chiba Institute of Technology | Yamazaki H.,Osaka University | Yamazaki H.,Osaka Fuji Corporation | Ohno A.,Chiba Institute of Technology | And 2 more authors.
Journal of Materials Engineering and Performance | Year: 2015

Throughout a long and distinguished career, the research activities conducted by Professor Ravindran have been characterized by the quest to generate fundamental as well as practical knowledge through collaborative efforts involving academia and industry as a basis for development of innovative manufacturing routes and improvement in performance of existing products and processes based on near-net-shape casting technologies. In this paper, the generation, validation, and implementation of new knowledge is illustrated by the Ohno Continuous Casting process, a heated mold system that permits the production of net-shape or near-net-shape products with a high-quality surface, controlled solidification structure, and significantly enhanced properties. © 2015, ASM International.


Okayasu M.,Akita Prefectural University | Takasu S.,Akita Prefectural University | Yoshie S.,Osaka Fuji Corporation
Journal of Materials Processing Technology | Year: 2010

The specific objective in this work is an exploration of the material properties produced by a recently developed continuous casting technique. The study focuses on an Al-Cu alloy provided by the Ohno continuous casting process. The experimental approaches give rise to unusual microstructural characteristic in the cast samples, namely a fine lamellar eutectic structure with unidirectional growth along its axial direction together with a regularly oriented lattice structure. Such microstructural characteristics significantly increase the tensile and fatigue properties. © 2010 Elsevier B.V.


Tanigawa D.,Osaka University | Abe N.,Osaka University | Tsukamoto M.,Osaka University | Hayashi Y.,Osaka University | And 3 more authors.
Science and Technology of Welding and Joining | Year: 2015

A Ni–Cr–Si–B alloy coating was produced on a type 304 stainless steel plate by laser cladding. A diode laser with a flat-top beam profile was used in this experiment. The effects of focused laser spot overlap on surface roughness (Ra) and Vickers hardness were investigated. Ra and the Vickers hardness of the cladding layers decreased as the overlap ratio increased. Cladding layers that maintained a hardness comparable to that of the source powder material were produced at overlap ratios of <70%. © 2015 Institute of Materials, Minerals and Mining


Okayasu M.,Akita Prefectural University | Yoshie S.,Osaka Fuji Corporation
Materials Science and Engineering A | Year: 2010

Examination of the mechanical properties of cast aluminum alloys (AC8A: Al-Si13-Ni1.4-Mg1.4-Cu1), created by the Ohno continuous casting (OCC) process, was conducted. The material strength and ductility of the OCC samples are twice as high as the same aluminum alloy produced by conventional gravity casting. The increase of material strength of the OCC sample is attributed to (i) tiny spherical α-Al grains, (ii) fewer cast defects and (iii) solid-solution strengthening by silicon. The high material ductility of the OCC sample is related to the regularly oriented crystal structure, where the crystal direction (111) in the cast sample is perpendicular to the casting direction, and (110) and (100) directions can be detected in the longitudinal direction of the sample. The yield stress of the OCC sample can be estimated by two different parameters: solid-solution strengthening, k√c, and grain size, ky/√d (Hall-Petch relation). © 2010 Elsevier B.V.

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