Kyushu University Academic Staff Educational and Research Activities Database
List of Papers
Kudo Kentaro Last modified date:2022.06.29

Assistant Professor / Manufacturing process lectureship / Department of Mechanical Engineering / Faculty of Engineering


Papers
1. Seiji Azukizawa, Fujio Tsumori, Hayato Shinoda, Kazuki Tokumaru, Kentaro Kudo, Kazunari Shinagawa, Development of printing system for magnetically anisotropic actuator, 21st International Conference on Miniaturized Systems for Chemistry and Life Sciences, MicroTAS 2017 21st International Conference on Miniaturized Systems for Chemistry and Life Sciences, MicroTAS 2017, 623-624, 2020.01, We propose a new three-dimensional (3D) printing system for magnetic elastomer, which is composed of photo curable resin dispersed with magnetic particles. The obtained structure is magnetic and flexible so that they can work as an actuator by changing the applied magnetic field. During the curing process, a magnetic field is applied to set magnetic anisotropy at the curing portion, and we can design the motion of the actuator using this anisotropy. It means that we can not only print the 3D-structure but also print the deformation of printed actuator..
2. K. KUDO, K. SHINAGAWA , H. MIURA, The Effects of Grain Size and Pore Size on the High Cycle Fatigue Behavior of Injection Molded Ti-6Al-4V Compacts, Advances in Powder Metallurgy & Particle Materials-2018,Proceedings of the 2018 International Conference on Powder Metallurgy & Particulate Materials, POWDERMET2018, 243-252, 2018.06.
3. Kentaro KUDO, Kazunari SHINAGAWA, Hideshi MIURA,, Effect of α + β region sintering on the mechanical properties of injection molded Ti-6Al-4V compacts, Mechanical Engineering Journal, 5, 4, No.17-00686, 2018.04.
4. Kentaro Kudo, Kazunari Shinagawa, Hideshi Miura, Evaluation of influence factors on the microstructure, static and dynamic mechanical properties of injection molded Ti-6Al-4V based compacts by multiple addition of Mo and B Elements, Funtai Oyobi Fummatsu Yakin/Journal of the Japan Society of Powder and Powder Metallurgy, 10.2497/jjspm.65.145, 65, 3, 145-153, 2018.01, Although the injection molded Ti alloys show sufficient tensile strength, their fatigue strength was significantly lower than that of wrought material. In this study, the effect of both additions of molybdenum and boron in the Ti-6Al-4V compacts on the microstructural refinement and strength was evaluated. The 4Mo-0.4B added compacts showed fine microstructure and resulted in high tensile strength. However, their fatigue strength was not improved. The degree of influence of oxygen content, relative density and grain size on the tensile strength was estimated, and the main factor of improving tensile strength was the grain refinement. Also, the cause that fatigue strength was not improved was the ratio of the maximum pore diameter to the grain diameter increased due to the microstructural refinement, so that the crack initiated from large pore..
5. Daiki Maede, Fujio Tsumori, Toshiko Osada, Kentaro Kudo, Visco-elastic control of elastomer with magnetic particles by applied magnetic field, IEEJ Transactions on Sensors and Micromachines, 10.1541/ieejsmas.138.48, 138, 2, 48-53, 2018.01, The purpose of this study was to explicate the mechanism of transition storage modulus and loss modulus under external magnetic field. Magneto-rheological elastomer (MRE) is expected to be used as damping material and actuator controlled by an external magnetic field. However, magnetic particles' behavior inside of MRE has not been explained completely. Especially, the mechanisms of loss modulus transition under external magnetic field has not been known well. We constructed a simple model with two magnetic particles, and try to make MRE behavior clear. In this report, we show a data of the viscoelastic property of MRE which consists of magnetic particles and polydimethylsiloxane (PDMS). The obtained viscoelastic property is explained by using two magnetic particles model..
6. Kentaro Kudo, Kazunari Shinagawa, Hideshi Miura, The effects of grain size and pore size on the high cycle fatigue behavior of injection molded Ti-6Al-4V compacts, 2018 International Conference on Powder Metallurgy and Particulate Material, POWDERMET 2018 Advances in Powder Metallurgy and Particulate Materials - 2018 Proceedings of the 2018 International Conference on Powder Metallurgy and Particulate Material, POWDERMET 2018, 243-252, 2018.01, Although titanium alloy compacts manufactured by metal injection molding (MIM) process have the same static mechanical properties as that of wrought materials with similar composition, their fatigue strength shows remarkably lower levels. In this study, improvement of the fatigue strength of injection molded Ti-6Al-4V alloy compacts was performed by refining the pore and grain sizes through different approaches such as the usage of fine powders, dual phase region sintering, and hydrogenation and dehydrogenation treatment. Especially, the effects of pore size and grain size on the fatigue strength were evaluated. Essentially, the relationship between the fatigue strength and the grain size for HIP treated compacts obeyed the Hall-Petch law. On the other hand, for the injection molded compacts with pores, it was found that the largest pore dominates the fatigue strength in the case of the large pore diameter ratio to the grain diameter, while the relative density influences on the fatigue strength when the pore diameter ratio is small..
7. Analytical Study of Size Effects on Sintering Deformation of Ceramic Plates.
8. Effects of differential speed rolling on orientation behavior of ceramic plate-like particles..
9. Deposition patterning for solidification of ceramic powder at room temperature by laser shock wave.
10. Sintering analysis of micro compacts with inhomogeneous powder packing structures.
11. Design of 3-dimensional cilia motion by external magnetic field driven artificial cilia.
12. Development of Magnetic Drive Actuator Fabricated by 3D Printing System for Magnetically Anisotropy.
13. Ryuma Marume, Fujio Tsumori, Kentaro Kudo, Toshiko Osada, Kazunari Shinagawa, Development of magnetic-field-driven artificial cilium array with magnetic orientation in each cilium, Japanese Journal of Applied Physics, 10.7567/JJAP.56.06GN15, 56, 6, 2017.06, Artificial cilia actuated by an applied magnetic field have been developed. In our previous report, we demonstrated actuated cilia of a few millimeters scale, which were fabricated by cutting a magnetic elastomer sheet. The fabricated artificial cilia worked similarly to natural cilia; however, they had a much larger structure than natural ones, and showed difficulty for use in pumping systems in micro-total analysis systems (μTAS) fields. Thus, our goal is further miniaturization. In this study, we introduce a new process of fabricating smaller pillar structures with a magnetic orientation in each pillar by ultraviolet (UV) laser machining. We also give different orientations to groups of pillars by the alternate laser machining of the mold and casting processes..
14. Kazuki Tokumaru, Fujio Tsumori, Kentaro Kudo, Toshiko Osada, Kazunari Shinagawa, Development of multilayer imprint process for solid oxide fuel cells, Japanese Journal of Applied Physics, 10.7567/JJAP.56.06GL04, 56, 6, 2017.06, Solid oxide fuel cells (SOFCs) are fuel cells made of ceramics. To increase the SOFC energy density, we developed an SOFC with a wavy electrolyte layer. As a wavy electrolyte has a larger reaction surface area than a flat electrolyte, a higher energy density could be obtained. Our proposed process is named micro-powder imprint (μPI) with a multilayer imprint process that is useful for fabricating a microscale pattern on a ceramic sheet such as an SOFC electrolyte layer. μPI is based on nanoimprint lithography; therefore, it also exhibits the same advantages of high resolution and mass productivity. The starting material for μPI is a compound sheet containing ceramic powder and binder materials consisting of thermoplastic resin. In this study, two different sheets were stacked into one sheet as a multilayer sheet for the μPI process to form a wavy compound sheet. As the initial state of the stacked sheet, including the mechanical properties of each layer, affects the final wavy shape, we changed the material composition. As a result, the SOFCs unit cell with a wavy electrolyte was fabricated. Note that the anode layer was formed at the same time. After adding the cathode layer, we succeeded in preparing a complete cell for testing power generation..
15. K. KUDO, H. ISHIMITSU, J. CHOE, T. OSADA, H. MIURA, K. SHINAGAWA, Effect of Grain Size on the Fatigue Properties of Injection Molded Ti-6Al-4V Compacts, Proceedings of the 2016 Powder Metallurgy World Congress & Exhibition, 3291789, 1-6, 2016.10.
16. T. OSADA, K. KUDO, R. HASHIKAWA, F. TSUMORI, H. MIURA, Control the Deformation of MIM Parts by the Powder Size Distribution, Proceedings of the 2016 Powder Metallurgy World Congress & Exhibition, 3307923, 1-6, 2016.10.
17. Fujio Tsumori, Hidenori Kawanishi, Kentaro Kudo, Toshiko Osada, Hideshi Miura, Development of three-dimensional printing system for magnetic elastomer with control of magnetic anisotropy in the structure, Japanese Journal of Applied Physics, 10.7567/JJAP.55.06GP18, 55, 6, 2016.06, In this paper, we report on a new system of three-dimensional (3D) printing for a magnetic elastomer that contains magnetic particles. Not only can we fabricate a three-dimensional structure, but we can also control the magnetically anisotropic property of each position in the structure using the present technique. Our new system employed photocurable poly(dimethylsiloxane) (PDMS) as the base material so that a method similar to a conventional 3D printing process with photolithography can be used. A magnetic powder was mixed with photocurable PDMS, and particle chain clusters were obtained by applying a magnetic field during the curing process. These chain clusters provide an anisotropic property in each part of the printed structure. We show some results of preliminary experiments and 3D printed samples in this paper. If the fabricated structure was placed under an applied magnetic field, each chain cluster will cause the rotational moment to be along the magnetic flux line, which can deform a soft matrix body. This deformation can be used as a magnetic actuator for the structure. Variable deformable structures could be developed using the present method..
18. Fujio Tsumori, Ryuma Marume, Akinori Saijou, Kentaro Kudo, Toshiko Osada, Hideshi Miura, Metachronal wave of artificial cilia array actuated by applied magnetic field, Japanese Journal of Applied Physics, 10.7567/JJAP.55.06GP19, 55, 6, 2016.06, In this paper, a biomimetic microstructure related to cilia, which are effective fluidic and conveying systems in nature, is described. Authors have already reported that a magnetic elastomer pillar actuated by a rotating magnetic field can work like a natural cilium. In the present work, we show examples of a cilia array with a metachronal wave as the next step. A metachronal wave is a sequential action of a number of cilia. It is theoretically known that a metachronal wave gives a higher fluidic efficiency; however, there has been no report on a metachronal wave by artificial cilia. We prepared magnetic elastomer pillars that contain chainlike clusters of magnetic particles. The orientation of chains was set to be different in each pillar so that each pillar will deform with a different phase..
19. Naoto Yoshigai, Kentaro Kudo, Fujio Tsumori, Toshiko Osada, Hideshi Miura, Anisotropic mechanical properties of ni-base superalloy compacts by direct laser forming technology, Funtai Oyobi Fummatsu Yakin/Journal of the Japan Society of Powder and Powder Metallurgy, 10.2497/jjspm.63.427, 63, 7, 427-433, 2016.01, As Ni-based superalloy has poor workability, direct laser forming (DLF) would be a powerful tool for fabricating the complex shaped Ni-based superalloy parts. We focused on the microstructure of the parts produced by DLF, the crystal grains of which grow along the building direction. This anisotropic microstructure is one of the major features of the parts produced by DLF, and which may cause anisotropic mechanical properties. In this work, the optimum laser-forming conditions such as laser power, laser scan speed, and powder feeding rate were determined by evaluating the density of the produced parts. Three types of tensile test pieces and two types of fatigue test pieces were fabricated in different building direction. They had higher ultimate tensile strength than that of JIS standards in wrought materials. However, their elongation was lower than that of JIS standards, and also the dispersion of elongation was large. On the other hand, fatigue limit was a little lower than the standard value. It was confirmed that the mechanical properties of Ni-based superalloy parts produced by DLF were different by a difference in building direction..
20. Ryuichi Hashikawa, Toshiko Osada, Kentaro Kudo, Fujio Tsumori, Hideshi Miura, Control the distortion of the large and complex shaped parts by the metal injection molding process, Funtai Oyobi Fummatsu Yakin/Journal of the Japan Society of Powder and Powder Metallurgy, 10.2497/jjspm.63.473, 63, 7, 473-478, 2016.01, Metal Injection Molding (MIM) is an effective way to manufacture small components with low cost and high precision. However, in the case of large components, it becomes difficult to control the distortion and cracking because of the big shrinkage during debinding and sintering process. Therefore it is important to optimize the condition of each process to reduce the distortion of MIM compacts. Moreover, powder size is also one of the most important parameters. The small particle powder shows high shrinkage and high density as compared to large particle powder during sintering process. In this study, blending of both powders was conducted and the influence of powder size distribution on the distortion of complex shaped parts was evaluated. A coordinate measuring machine, which is a 3D device for measuring the physical geometrical characteristics of an object, was used to measure the distortion. Finally, through controlling the distribution of particle size, distortion of the comparatively large and complex shaped MIM compacts was successfully restrained..
21. Fujio Tsumori, Kazuki Tokumaru, Kentaro Kudo, Toshiko Osada, Hideshi Miura, Development of corrugated ceramic sheet for SOFC electrolyte by micro imprint process, Funtai Oyobi Fummatsu Yakin/Journal of the Japan Society of Powder and Powder Metallurgy, 10.2497/jjspm.63.519, 63, 7, 519-523, 2016.01, Yttria-stabilized zirconia (YSZ) has been used for an electrolyte of solid oxide fuel cells (SOFC). To enhance the efficiency of SOFC, we developed a corrugated, or wavy-shaped, YSZ sheet for the electrolyte. As the corrugated sheet has larger surface area than a flat-type sheet, higher energy density can be obtained. We have proposed micro powder imprint (μPI) with multi-layer imprint process to fabricate micro scale pattern on the both surfaces of a thin YSZ sheet. The μPI is a combined process of nano imprint lithography and powder metallurgy; the resolution is high, and the process is mass-productive. In this work, we selected a compound material containing YSZ powder and a binder consisting of thermoplastic resin as a starting material. The compound sheet was prepared by tape casting from slurry and was imprinted by a fine-patterned mold with stacked on a silicone rubber sheet. The silicone rubber was so flexible that micro patterns on the both sides of the compound sheet was obtained after imprint. In the present work, the process condition of μPI and the heat program of debinding and sintering were also considered. As a result, a wave-type sintered YSZ sheet without significant defects was successfully obtained..
22. Jungho Choe, Toshiko Osada, Kentaro Kudo, Fujio Tsumori, Hideshi Miura, Effect of minor boron addition on the fatigue strength and high temperature properties of injection molded Ti-6Al-4V compacts, Funtai Oyobi Fummatsu Yakin/Journal of the Japan Society of Powder and Powder Metallurgy, 10.2497/jjspm.63.451, 63, 7, 451-456, 2016.01, Ti-6Al-4V alloy has attracted a lot of attention from the automotive and aerospace industries because of their outstanding specific strength and corrosion resistance. On the other hand, Ti-6Al-4V alloy has normally poor workability because of the low thermal conductivity and the low elastic modulus. Metal injection molding (MIM) process is expected to manufacture a complex part with near net shape and reduce the manufacturing cost. However, Ti-6Al-4V alloy compacts by MIM process had a problem of low fatigue strength compared to wrought material. In this study, we tried to add a minor amount of boron using TiB2 powder for improving the fatigue strength. Addition of boron resulted refinement of the grain size of lamellar structure, which lead to increase the high cycle fatigue strength and fatigue limit. In addition, tensile properties at high temperature was investigated..
23. Toshiko Osada, Yusuke Kanda, Kentaro Kudo, Fujio Tsumori, Hideshi Miura, High temperature mechanical properties of TiAl intermetallic alloy parts fabricated by metal injection molding, Funtai Oyobi Fummatsu Yakin/Journal of the Japan Society of Powder and Powder Metallurgy, 10.2497/jjspm.63.457, 63, 7, 457-461, 2016.01, It is not easy to fabricate the complicate shaped titanium aluminide (Ti-Al) components by conventional methods such as machining or forging, and casting leads to inhomogeneous microstructures. Metal injection molding (MIM) has the potential to be a cost-efficient process and near net shape technique, especially for the complex shaped mass-produced components. In this study, Ti-Al intermetallic alloy compacts were fabricated through MIM technique. Sound compacts with over 95 % of relative density and without any warpage or defects were obtained thorough MIM process. Different microstructures of duplex, near lamellar, and full lamellar were obtained by changing the sintering temperature. Their tensile strength at room and high temperature is 85 to 90 % of that of wrought material. Tensile strength of MIM compact would be expected the same level with cast materials by optimization of sintering conditions, densification by HIP treatment and so on..
24. Kentaro Kudo, Sek Kin Wai, Toshiko Osada, Fujio Tsumori, Hideshi Miura, Improvement of mechanical properties of injection molded ni-base superalloy compacts, Funtai Oyobi Fummatsu Yakin/Journal of the Japan Society of Powder and Powder Metallurgy, 10.2497/jjspm.63.462, 63, 7, 462-467, 2016.01, Superalloy has been used for aerospace application because of their excellent attributes of high strength and corrosion resistance at high temperature. Inconel 718 is one of the representative Ni-based superalloy. Generally, superalloy has poor workability, especially high tool wear by machining, so that it is not easy to produce the components of complex shaped parts at low cost. To overcome such as the problem, metal injection molding (MIM) process would be a useful technique which offers net shape production, high design flexibility, and high cost efficiency for mass production. In this study, gas-atomized fine alloy powder of Inconel 718 was prepared for MIM process, and the mechanical properties of injection molded compacts were investigated. The relative density over 99.7 %, which is much higher than density of usual MIM compacts, was obtained by supersolidious liquid-phase sintering. Furthermore, injection molded Inconel 718 showed high fatigue strength comparable to the wrought materials, because the pore size of the MIM compacts was smaller than the inclusion size of wrought materials. And it was found that the grain size was more dominant than pore size against the fatigue failure of MIM Inconel 718 with near full density..
25. Kentaro Kudo, Hiroyoshi Ishimitsu, Toshiko Osada, Fujio Tsumori, Hideshi Miura, Static and dynamic fracture characteristics of the MIM Ti-6Al-4V alloy compacts using fine powder, Funtai Oyobi Fummatsu Yakin/Journal of the Japan Society of Powder and Powder Metallurgy, 10.2497/jjspm.63.445, 63, 7, 445-450, 2016.01, Titanium alloys show not only the excellent mechanical properties but also good biocompatibility. However, they show normally poor machinability, which become the disadvantage of high processing cost. Metal injection molding (MIM) process is one of the techniques to improve that drawback. Because MIM process can produce the three dimensional complex shaped parts at low cost. Ti-6Al-4V is a typical titanium alloy and the MIM compacts show high static strength as same as wrought materials. However, their fatigue strength is a little low level as compared to wrought materials. To improve the mechanical properties of Ti-6Al-4V alloy compacts, it is important to refine the grain size and increase the relative density. In this study, the effects of the particle size of the powders on the mechanical properties were investigated. The use of a fine powder improved the mechanical properties because of their high density. Moreover, the crystal grain growth was restrained as compared to the case of the same relative density using larger powder..
26. Fujio Tsumori, Simon Hunt, Kentaro Kudo, Toshiko Osada, Hideshi Miura, Wavy micro channels in micropatterned ceramic sheet formed by combined process of laser beam machining and imprinting, Funtai Oyobi Fummatsu Yakin/Journal of the Japan Society of Powder and Powder Metallurgy, 10.2497/jjspm.63.511, 63, 7, 511-518, 2016.01, Micro channels made of polymers are commonly used for MEMS and μTAS (micro-total analysis system) devices. In this research, we developed a process for fabricating a ceramic sheet with micro channels. The developed process is based on powder metallurgy process. A compound material, a mixture of ceramic powder and polymer, was prepared as sheet material. We employed laser machining to machine the sacrificial layer to form micro channels inside the sheet. We also employed imprinting, which is a process of pressing with a mould while heating, to form a structure with surface patterns and micro channels curving along with it. After the imprinted sheet was debound and sintered by heating, a ceramic sheet with micro-surface patterns and micro channels was obtained. As ceramics have high heat durability and low chemical reactivity, ceramic micro channels can be used for flow sensors or chemical reaction testers operated in harsh environments, such as high temperature or mechanical parts operated with reactive chemicals. In addition, by imprinting wavy patterns, the surface area can be increased. Therefore high efficiency heat exchangers can be built. Moreover, this method can be applied on SOFCs (solid oxide fuel cell) by fabricating YSZ (yttria stabilized zirconia) micro channels..
27. Mechanical properties of MIM super high strengthening sintered low alloy steels with fine heterogeneous.
28. Surface Patterning on Ceramic Sheet by Microimprinting Process.
29. Visco-elastic control of elastomer with magnetic particles by applied magnetic field.
30. 4-dimensional Printing Process Using Elastomer Dispersed with Magnetic Particles.
31. Deformation Control of Large Sized MIM Parts.
32. Yohei Sano, Toshiko Osada, Kentaro Kudo, Fujio Tsumori, Hideshi Miura, Makiko Tange, Shigeo Tanaka, Effect of Cr content on the magnetic properties of Fe-Cr soft magnetic material by MIM process, Funtai Oyobi Fummatsu Yakin/Journal of the Japan Society of Powder and Powder Metallurgy, 10.2497/jjspm.62.431, 62, 8, 431-436, 2015.08, In recent years, the soft magnetic material parts have been widely used in the fields of industrial equipments, consumer electronics, automobiles, and so on. To fabricate these soft magnetic material parts, electrical steel and P/M method is normaly used. With the increase of fabricating complex shaped parts, processing method with more flexibility in design also be needed. For this reason, MIM process is hoped to be a near-net-shape, cost reduction and mass production method which can fabricate three-dimensional complex shaped parts. Fe-Cr-based soft magnetic material is developed in 1960s∼1970s to be used in corrosive environments. Because it is less expensive than the PB permalloy. Mainly composition comprising a 13 %Cr or higher is used to make material stable. However, the maximum magnetic flux density of material decreases with increase of Cr content. In this research, the effect of Cr content on the magnetic properties under DC and AC magnetic field were investigated by mixing SUS430L alloy powder and iron powder..
33. J. CHOE, T. OSADA, K. KUDO, F. TSUMORI, H. MIURA, Improvement of Fatigue Strength for Titanium Alloy Compacts by MIM, Advances in Powder Metallurgy & Particle Materials-2015,Proceedings of the 2015 International Conference on Powder Metallurgy & Particulate Materials, POWDERMET2015, 04-71-04-78, 2015.07.
34. Kentaro Kudo, Terukazu Tokuoka, Hyungoo Kang, Toshiko Osada, Fujio Tsumori, Hideshi Miura, Effect of mezzo-heterogeneous microstructure and rolling on the rolling contact fatigue strength of sintered high Ni alloy steels, Funtai Oyobi Fummatsu Yakin/Journal of the Japan Society of Powder and Powder Metallurgy, 10.2497/jjspm.59.258, 59, 5, 258-263, 2012.05, This study aims to improve the fatigue strength of P/M gears and to substitute P/M gears for conventional wrought steel gears with reduced manufacturing costs. The 4600 series sintered alloy steels with mixed elemental powders show the mezzo-heterogeneous microstructure which consists of high-hard Ni rich areas and the surrounding martensitic structures. This mezzo-heterogeneous structure causes high strength to the products. In this paper, we discuss the effects of Ni contents on the contact fatigue strength, and the effect of the pore size is also discussed for further strengthening. Especially, from the evaluation of the area of isolated pores in the densified surface layer after the rolling, it was found that the decrease of pore sizes is very important to improve the contact fatigue strength..
35. Shigeru Unami, Takuya Goushi, Kentaro Kudo, Fujio Tsumori, Hyung Goo Kang, Hideshi Miura, Improvement of surface densificaron and fatigue strength by tooth root rolling of sintered ferrous alloy gear added Mo, Funtai Oyobi Fummatsu Yakin/Journal of the Japan Society of Powder and Powder Metallurgy, 10.2497/jjspm.58.692, 58, 11, 692-696, 2011.11, Surface rolling were carried out using P/M spur gears of 0.6Mo-0.2C partially alloyed sintered steel with the density of 7.18 g/cm
3
. A CNC form rolling machine of axis intersection type was employed, and an unmodified screw-shaped rolling tool was prepared. Then, porosity distributions in the surface layer of rolled gear teeth root were measured and the effects of the surface rolling on the selective surface densification behaviors were evaluated. Moreover, to obtain higher fatigue strength, reverse rolling was introduced to standard gears. As a result, the porosities in the tooth root were sufficiently reduced at 700/μm feed in rolling process. Furthermore, a profile shifted gear was prepared to increase the effect of surface rolling. After case hardening, the single tooth bending fatigue durability reached to about 83% of the case hardened wrought steel gears of SCM415..
36. Terukazu Tokuoka, Torn Yamamoto, Kentaro Kudo, Fujio Tsumori, Hideshi Miura, Takao Nishioka, Effect of mezzo-heterogeneous microstructure and rolling on the tooth root bending fatigue properties of sintered Ni alloy steel gears, Funtai Oyobi Fummatsu Yakin/Journal of the Japan Society of Powder and Powder Metallurgy, 10.2497/jjspm.58.350, 58, 6, 350-354, 2011.06, This study aims at reducing costs of high load gear manufacturing, and substituting P/M gears for conventional wrought steel gears. In order to improve the fatigue strength of P/M gears, we focused on the rolling and the high performance sintered and heat treated 4600 series alloy steels with mezzo-heterogeneous microstructure which were made from the mixed elemental powders. The fatigue strength was determined by single tooth root bending fatigue test machine, and the effect of mezzo-heterogeneous microstructure and rolling on the fatigue strength was mainly investigated. The endurance limit at N=3.0× 106 of the 500 μn rolled 6%Ni alloy steel gear compact showed 950 MPa which value is about 2/3 of the case hardened wrought steel (SCM415) gears. However, the endurance limit of rolled and heat treated gear compact showed lower value (630 MPa) as compared to as-rolled gear compact. This seems to be due to the decreasing the compressive residual stress by heat treatment and unfavorable mezzo-heterogeneous microstructures..
37. T. TOKUOKA, Y. NAKAHARA, K. KUDO, T. NISHIOKA, H. MIURA, Effect of Microstructure on the Rolling Contact Fatigue Strength of 4600 Steel P/M Compacts, European PM Conference Proceedings, European Congress and Exhibition on Powder Metallurgy, 1-10, 2010.10.