Yorihiro Yamashita

Effect on beam profile of Ti alloy plate fabrication from powder by sputter-less selective laser melting

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.

Synchrotron x-ray induced real time observations of CoCr alloy layer formation by micro laser cladding

The direct injection type laser cladding system using combined multi lasers, which supplies a clad powder from a center nozzle, was developed for realize of low dilution area and micro cladding. A fiber coupled diode laser was employed. The six-diode lasers were guided to focusing head with every optical fiber, which core diameter is 100 μm. Beam profile at focal point of the combined six lasers was set a spot diameter of 300 μm by CCD camera. Here, A cobalt-chromium alloy (CoCr-alloy) called by Stellite, which has excellent properties such as wear resistance, corrosion resistance and resistance to environment, was used as a cladding material. The focusing head has a function to supply a CoCr-alloy powder at a focal point from a center nozzle. When the laser irradiation and powder supply are simultaneously performed toward to a stainless steel 304 substrate, the CoCr-alloy powder was melted and solidified on the substrate to form a cladding layer. The melting and solidification process for CoCr-alloy was observed in real time using synchrotron radiation imaging technique at BL22XU in SPring-8. From results, it was clarified that the CoCralloy melt-solidification phenomenon greatly differs for laser output power. At the output power of 60W, it was found that a minimum amount of molten pool was formed and then solidified to form the cladding layer.

Experimental study on Ti alloy plate fabrication by vacuum selective laser melting

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.

Experimental investigation on crystal orientation of Ti6Al4V plate fabricated by vacuum SLM process

Ti6Al4V (Ti64) plate was fabricated from powders in vacuum at 10−2 Pa by selective laser melting (SLM) method with single mode fiber laser. Ti64 has a crystal orientation of alpha α + β type. In order to investigate the crystal orientation, a X-ray diffraction in continuous scanning mode and an energy dispersive X-ray spectroscopy were conducted. From the results, it can be found that at the powder, the peak of α (1011), α (0002), α (1010) and α(1012) crystal orientations is detected to be composed mainly of martensitic alpha. Diffraction peaks corresponding to β(110) were detected in vacuum SLM processed samples.Ti6Al4V (Ti64) plate was fabricated from powders in vacuum at 10−2 Pa by selective laser melting (SLM) method with single mode fiber laser. Ti64 has a crystal orientation of alpha α + β type. In order to investigate the crystal orientation, a X-ray diffraction in continuous scanning mode and an energy dispersive X-ray spectroscopy were conducted. From the results, it can be found that at the powder, the peak of α (1011), α (0002), α (1010) and α(1012) crystal orientations is detected to be composed mainly of martensitic alpha. Diffraction peaks corresponding to β(110) were detected in vacuum SLM processed samples.