Akihiko Ikuta

Fundamental Study on Adhesion Mechanism of Difficult-to-Machine Materials during Cutting. 2nd Report. Effect of Reaction Layer on Diffusion Bondability between Various Titanium Alloys and Cemented Carbide.

In this study, in order to clarify the cause of the difference of adhering phenomenon between various titanium alloys and cemented carbide (K 10) in cutting process, diffusion bonding joint of these alloys was produced, and the relationship between high-temperature bending strength of the joint and form of reaction phases in bonded interface was examined. Though the diffusion bonding was done in temperature range from 1073K to 1473K and for the holding time of 0s on either titanium alloy, titanium carbide was formed as reaction phase. At Ti, Ti-6Al-4V and βC-Ti, forms of titanium carbide were massive, hump and layered types, respectively. As a result of 4 point bending test of bonded joint of each alloy at the testing temperature of 1373K, βC-Ti was high in comparing the bending strength with Ti and Ti-6Al-4V. As a result of observing the rupture position of test piece for bend test, in Ti, Ti-6Al-4V and βC-Ti, the rupture occurred in Ti inside, interface between reaction phase and Ti and cemented carbide inside, respectively. From the result of the diffusion bonding, the reason why βC-Ti is easy to adhere by the cutting process is because in βC-Ti, it forms the layered titanium carbide phase between the cemented carbide, and because it becomes a firm bonded joint.

Joining between Stainless Steel and Carbon Steel with Thermal Spray Coating of Ni Based Self-Fluxing Alloy. Study on Flame Spraying (Report 5)

The joining between stainless steel (SUS304) and carbon steel (SS400) was carried out using thermal spray coating of nickel based self-fluxing alloy under atmospheric conditions for basic data. The size of joining specimen is 50 mm in length and 10 mm in diameter. After the each edged surface of SUS304 and SS400 specimens were blasted by used steel grid material sized No. 70, those were sprayed with self-fluxing alloy (S.F.A.) at the each surface of both specimens coated about 100μm in thickness.The effects of joining conditions on the structure and strength of joining were studied.The results are summarized as follows:(1) The maximum tensile strength at the joint part using R notch specimen was about 579 MPa under condition of 30 sec raising time and 60 sec holding time at 1373 K temperature.(2) The hardness gradient was not observed near the joining zone in the Vickers hardness distribution of the both materials. Furthermore, the Vickers hardness distribution near the joining zone of SUS304 was about Hv120, that was lower than base metal because of the annealing effect.(3) The microstructure near the joining zone did not indicate the martensitic structure, the carburized and the decarburized layer because of its lower cooling rate. The structure near the joining zone of SUS304 was indicated in the annealed twin at the transgranular.(4) By the EPMA line analysis across the joining zone, Cr, Ni, and B were not observed because the inserted material S.F.A. was very little diffused and the most of it was discharged out of the joining part. The elementary analysis of Fe was indicated sligthly concentrated gradient.