Hajime Miyazawa

Chemical vapour deposition of a diamond coating onto a tungsten carbide tool using ethanol

Abstract Diamond coating of a tungsten carbide alloy using the hot filament chemical vapour deposition process was investigated for application to tool manufacture. Previously, diamond deposition onto a cobalt-rich tungsten carbide alloy has been considered to be impossible using this process. However, it was found that using ethanol as the carbon source a good diamond coating layer could be obtained. Moreover, when a diamond-coated tool was applied to the shearing of an aluminium plate 2.5 mm thick, no abrasion of the diamond coating and no adhesion of chips of the sheared material to the tip of the tool were found even after 5 × 10 4 punchings, demonstrating the excellent hard coating effect as well as reasonably good adhesion of the coated diamond layer.

IMPROVED MICROSCRATCH HARDNESS OF ION-PLATED CARBON FILM BY NITROGEN INCLUSION EVALUATED BY ATOMIC FORCE MICROSCOPE

Nitrogen‐containing carbon films where deposited by reactive ion plating under a pure nitrogen ambient. Knoop hardness, microindentation hardness, and microscratch hardness of these films were evaluated. Indentation hardness, such as Knoop hardness and microindentation hardness, is influenced by surface roughness and substrate hardness, so the effect of nitrogen inclusion on the hardness cannot be clearly evaluated. In contrast, an atomic force microscope can clearly evaluate the effect of nitrogen inclusion on scratched wear depth.

Synthesis of thick DLC film for micromachine components

Abstract A diamond-like carbon (DLC) film generally exhibits low adhesion strength, i.e. easiness of peeling off from the surface of a substrate due to the internal compressive stress, as high as 2 GPa, generated in the film, thus resulting in the limitation of the film thickness to as small as 1–3 μm. The purpose of this study is to establish a technology, which can synthesize DLC film thicker than 30 μm, for micromachine components, using the RF plasma chemical vapor deposition (CVD) method. The results showed that the introduction of silicon can reduce the internal stress to approximately 0.8 GPa, and the formation of a multilayered structure in addition to silicon can reduce it further to 0.68 GPa. Thus, these measures succeeded in reducing the stress by as much as 40% compared with that in the film synthesized by conventional techniques. Furthermore, the reduction of the stress allowed the formation of a freestanding thick DLC film that can be used as the material for micromachine components. Microcutting and grooving performance of the film, by the usage of YAG laser and focused ion beam (FIB) techniques, are shown. Finally, we fabricated a DLC rod of 30-μm length and 5-μm diameter.

Modification of nanometer scale wear of nitrogen-containing carbon films due to ion implantation

Abstract Nitrogen-containing carbon (CN) films were deposited by reactive ion plating in nitrogen ambient. The effects of nitrogen inclusion in thin carbon film on microwear resistance were investigated using an atomic force microscope. The depth of the wear scar on nitrogen-containing carbon film was one-tenth that on ion-plated carbon film. Nitrogen-containing carbon films have superior microwear resistance. N+ implantation into nitrogen-containing carbon film decreases the microwear resistance. However, N+ implantation into ion-plated carbon films increases the microwear resistance.

Laser‐assisted thermochemical processing of diamond

A new technique of contamination‐free thermochemical processing of diamond is proposed. A diamond plate, which is placed on a metal plate, is treated thermochemically from its lower surface, in liquid, using a laser as the heat source. A focused Q‐switched YAG laser beam was introduced, which passed through the liquid and diamond, onto the metal plate. The laser beam heats up the metal, and thereby, the lower surface of the diamond is etched by thermochemical interaction with the liquid. Comparison of the liquids, de‐ionized water, and KOH solution, proved that KOH solution is preferable to water with respect to the stability of machining and smoothness of the prepared surface.

SUPERCONDUCTIVE FILMS BY LASER POST-TREATMENT OF THERMAL-SPRAYED FILMS

Abstract In an attempt to produce a thick superconductive film of large area, an experimental study was conducted on the preparation of the film through laser post-treatment of thermal-sprayed oxide ceramic film. The ceramic powder of Bi-(Pb)-Sr Ca-Cu-O system was used as raw material. The powder was sprayed onto a stainless steel substrate using two types of spraying systems, conventional plasma spraying system and lower temperature hypersonic spraying system both followed by CO2 laser beam irradiation with oxygen gas flow to remodify the superconductive crystals in the films. The results showed that, though laser post-treatment can produce superconductive crystals in both sprayed films, higher critical temperature Tc (end) was obtained for the film prepared by the hypersonic spraying system.

Sintered diamond cutting inserts with chip breaker prepared by laser technique

Abstract A chip breaker pattern is formed on the surface of a sintered diamond cutting insert in KOH solution using a laser technique which is applicable to a variety of breaker patterns. A pulse yttrium—aluminum—garnet laser of 1.06 μm wavelength is used. The processed breakers are first evaluated using SEM (scanning electron microscope), WDX (wave dispersive X-ray analyzer) and a surface-roughness measuring instrument, followed by cutting of an aluminum alloy rod. SEM micrographs and the results of EDX analysis show that there is no heat-affected-zone on the surface processed in liquid. In contrast, a significant increase in the amount of cobalt, which is used as binder, is detected on the surface processed in air. Furthermore, roughness of the processed surface can be made equal to or smaller than the grain size of the diamond by controlling the laser conditions. Results of the cutting test using inserts with chip breaker prepared in liquid has proven that a detrimental ribbon-like strip of the metal is broken into short pieces under various conditions of feed rate and depth of cut, whereas the insert with a breaker prepared using the laser technique in air easily cracked.

Laser microcontouring of diamonds

A basic study on laser microcontouring of diamonds is conducted. A single-crystal diamond plate synthesized at high pressure and high temperature, and free-standing polycrystalline diamond film prepared by the hot-filament CVD method are used as the materials to be processed. A Q-switched single-mode YAG laser beam is irradiated onto the diamond surface. Diamonds are processed in oxygen gas and in liquid to investigate the effect of atmosphere on the quality of the process. The experiment is conducted on an X-Y table enabling such contour motions as a simple circular or complex gear profile. Results are evaluated using SEM image, Raman spectral and surface roughness analyzer systems. Results show that 1) both single crystal and CVD film can be processed in oxygen atmosphere but a heat-affected zone of amorphous carbon appears, whereas surfaces processed in liquid do not contain any heat-affected zone for either form of diamond, 2) CVD film is processed from its upper surface whereas single crystal is processed from its bottom surface in liquid, 3) processing in liquid yields far better surface roughness than that yielded in oxygen atmosphere in grooving of single-crystal diamond.A basic study on laser microcontouring of diamonds is conducted. A single-crystal diamond plate synthesized at high pressure and high temperature, and free-standing polycrystalline diamond film prepared by the hot-filament CVD method are used as the materials to be processed. A Q-switched single-mode YAG laser beam is irradiated onto the diamond surface. Diamonds are processed in oxygen gas and in liquid to investigate the effect of atmosphere on the quality of the process. The experiment is conducted on an X-Y table enabling such contour motions as a simple circular or complex gear profile. Results are evaluated using SEM image, Raman spectral and surface roughness analyzer systems. Results show that 1) both single crystal and CVD film can be processed in oxygen atmosphere but a heat-affected zone of amorphous carbon appears, whereas surfaces processed in liquid do not contain any heat-affected zone for either form of diamond, 2) CVD film is processed from its upper surface whereas single crystal is proc...

Improvement of superconductive characteristics by laser surface treatment

Abstract The effect of laser beam irradiation onto the surfaces of superconductive materials of Bi system is discussed. Results of SEM observation, XRD analysis and measurement of critical temperature of laser treated surfaces indicate that the treatment can improve crystal conditions of the system.

Possibility of connecting bulks of Bi system by the laser irradiation

Abstract Laser treatment has been successful in rapidly realizing superconductors of Bi system. We applied this to easy connection between two bulks and obtained indication of successful result.