Titanium alloy (Ti-6Al-4V) ,which has a crystal orientation of α+β type, are clinical employed for an artificial bone and a hard tissue implant for human body because of light, nonmagnetic, weather resistance and biocompatibility, but it is difficult to form a complicated structure, as a bionic structure, owing to a difficult-to-cut machine material. Thus, titanium alloy plates were fabricated by selective laser melting (SLM) in vacuum. Melting and solidification process were captured with high speed video camera, it was found that sputter was depended on the surface roughness. The sputter-less fabrication for SLM in vacuum was developed to minimize the surface roughness to 0.6μm at the laser scanning speed of 10mm/s. It was also determined that crystal orientation was evaluated with X-ray diffraction (XRD). It was recorded from the powder peaks of α (1011), α (0002), α (1010), and α (1012) that the crystal orientation is composed mainly of martensitic alpha by XRD analysis. Diffraction peaks corresponding to β (110) were detected in vacuum SLM processed samples.
Laser cladding technique is widely used for industrial application such as oil, energy industry, and aircraft and so on because it is able to repair and to form a near net shape. This process have been employed infrared lasers with wavelength of 0.8-10.6μm since output power of these lasers have over 1000W. Metal processing efficiency was, however, low in these wavelength, because the absorption was low. Thus, we developed the laser cladding system with blue direct diode laser at the wavelength of 445nm. 6 blue diode lasers was combined on the focusing spot to reach the output power of 100W by a lens, which one blue diode laser module was maximum output power of 20W. By using this laser cladding system, a pure copper film coating on a SUS304 stainless steel plate was demonstrated from a copper powder. As the result, the copper layer was formed on SUS304 stainless steel plate at the width of 322μm and thickness of 534μm was formed on the substrate.
Titanium (Ti) is widely used as biomaterial, for example artificial bone, joint etcetera. Femtosecond laser can be used to form periodic nanostructures on Ti surface, and the structures help to control cell elongation. The period of the periodic nanostructures on Ti under atmospheric condition is about 70 to 80% compared with the laser wavelength. However, the mechanism of periodic nanostructure formation by femtosecond laser irradiation has not been clarified yet. Thus, we focused on Surface Plasmon Polariton (SPP) model, which was proposed as a model for formation of periodic nanostructures by femtosecond laser irradiation. In this model, standing waves are generated on the material surface caused by excited electrons on the material surface by laser irradiation. The wavelength of the standing waves depends on the permittivity of the surrounding medium, and the period of the periodic nanostructures also depends on the wavelength of the standing waves. Therefore, it is considered that the period of the nanostructures varies by changing the permittivity at the laser irradiation interface2,3).In this study, a polyethylene terephthalate (PET) films which has permittivity of 3.0, and a polymethyl methacrylate (PMMA) films which has permittivity of 3.4 were contacted on Ti surface by using contact jig and then the femtosecond laser at a wavelength of 800 nm was irradiated to create periodic nanostructures. As a result, periodic nanostructures with a period of 440 nm was formed on Ti under PET adhesion condition, and periodic nanostructures with a period of 380 nm was formed on Ti under PMMA adhesion condition. On the other hand, periodic nanostructures with a period of 600 nm was formed on Ti under atmospheric condition. It was found that the period of periodic nanostructures can be controlled by changing the permittivity of the medium adhered to Ti.
We demonstrated that a Ti-6Al-4V plate, which is clinically used for artificial bone and hard tissue implant in human body because of their light and biocompatibility, were fabricated by SLM process in vacuum. The chamber’s pressure was set to 1.0×10-3 Pa to prevent the Ti64 powder from oxidizing. The base plate of the powder bed was vertically dropped in determined steps, and Ti64 powder supplied from the powder feeder was then smoothed by a roller on top of the powder bed. The single-mode fiber laser irradiated and melted the powder bed to make a molten pool in order to form 2D metallic structures In order to investigate the laser melting and solidification dynamics, a process of Ti 64 plate fabrication was captured by high speed video camera. It was also determined that crystal orientation was evaluated with X-ray diffraction (XRD) and energy dispersive X-ray (EDX) spectroscopy From EDX analysis, the chemical compounds were not changed from powder to fabricated sample. And it was recorded from the powder peaks of α (1011), α (0002), α (1010), and α (1012) that the crystal orientation is composed mainly of martensitic alpha by XRD analysis. Diffraction peaks corresponding to β (110) were detected in vacuum SLM processed samples.
A carbon fiber reinforced plastic (CFRP) is widely used for automobile, aircraft and so on, because of having high strength, lightweight and weather resistance. A laser is one of useful tools for cutting CFRP. However, a matrix evaporated zone (MEZ) is formed around the laser irradiation area since heat property of the resin is different from that of carbon fiber. It is required for optimizing the laser processing condition to minimize the MEZ. In our experiment, the CFRP plate was cut with a nanosecond laser under air and Ar gas ambience. The ambient gas is an important factor for reduction of MEZ since formation of MEZ might be caused due to an oxidization of carbon fiber and epoxy resin. In order to evaluate the oxidization, spectroscopic analysis was carried out to investigate an ablation plume under air and Ar gas. Furthermore, a surface on CFRP plate was observed with a scanning electron microscope (SEM). As the results, the cutting quality for argon is better than that for air, and the MEZ for Ar gas is smaller than than that for air.
Titanium (Ti) is one of the most used biomaterials in metals. However, Ti is typically artificial materials. Thus, it is
necessary for improving the biocompatibility of Ti. Recently, coating of the titanium dioxides (TiO2) film on Ti plate has
been proposed to improve biocompatibility of Ti. We have developed coating method of the film on Ti plate with an
aerosol beam. Periodic structures formation on biomaterials was also a useful method for improving the biocompatibility.
Direction of cell spreading might be controlled along the grooves of periodic microstructures. In our previous study,
periodic nanostructures were formed on the film by femtosecond laser irradiation at fundamental wave (775 nm). Period
of the periodic nanostructures was about 230 nm. In cell test, cell spreading along the grooves of the periodic
nanostructures was observed although it was not done for the film without the periodic nanostructures. Then, influence
of the period of the periodic nanostructures on cell spreading has not been investigated yet. The period might be changed
by changing the laser wavelength. In this study, the periodic nanostructures were created on the film with femtosecond
laser at 775nm and 388 nm, respectively. After cell test, cell spreading along the grooves of the periodic nanostructures
was observed on 775 nm and 388nm laser irradiated areas. Distribution of direction of cell spreading on laser irradiated
area was also examined. These results suggested that controlling the cell spreading on periodic nanostructures with
period of 230 nm was better than that with period of 130 nm.
A carbon fiber reinforced plastic [CFRP], which has high strength, light weight and weather resistance, is attractive material applied for automobile, aircraft and so on. The laser processing of CFRP is one of suitable way to machining tool. However, thermal affected zone was formed at the exposure part, since the heat conduction property of the matrix is different from that of carbon fiber. In this paper, we demonstrated that the CFRP plates were cut with UV nanosecond laser to reduce the heat affected zone. The ablation plume and ablation mass were investigated by laser microscope and ultra-high speed camera. Furthermore, the ablation model was constructed by energy balance, and it was confirmed that the ablation rate was 0.028 μg/ pulse in good agreement with the calculation value of 0.03 μg/ pulse.