In order to clarify the bonding mechanism and to control the quality of cold-sprayed coatings, it is necessary to accurately measure the in-flight velocity and impact velocity of a projectile. In this study, the in-flight velocity of an aluminum alloy (A2017) 1 mm sphere shot from a small two-stage light gas gun was measured as being 1 km/s using a laser-cut velocity measurement technique. So as to estimate the impact velocity of the projectile, the projectile was caused to impact targets made of aluminum (A1050), copper (C1012), mild steel (SPCC), and stainless steel (SUS304). After the impact tests, the impact crater shapes of the targets was measured using scanning electron microscopy(SEM), energy dispersive X-ray spectroscopy (EDS), and laser microscopy. The impact velocity of a projectile was estimated from obtained crater depth of the targets. In addition, microstructures of the interface between projectile and target were analyzed by EDS, electron backscattered diffraction (EBSD) and transmission electron microscopy (TEM).

In this investigation, particle image velocimetry (PIV) and direct imaging are used to measure particle velocities during cold spraying. Four feedstock powders were sprayed, including Ni, WC-Co, carbonyl Fe, and Cr steel. Multiple exposures at 500 ns intervals were used to measure in-flight particle velocities via direct imaging with a high shutter speed camera. Velocimetry measurements were made with a double-pulse laser and a high-resolution camera. With the minimum frame straddling time set to 100 ns, a maximum particle velocity of 1052 m/s was measured.

In this study, particle image velocimetry (PIV) is used to measure WC particle velocity during HVAF spraying. Measured velocities are compared with calculated velocities obtained using open source CFD software. Numerical simulation is also used to investigate particle temperatures. With the HVAF gun used, maximum particle velocity is reached around 18 mm from the nozzle exit with a corresponding gas temperature of 1400 K.

In this study, the dust explosion properties of aluminum, titanium, zinc, and iron based alloy powders were evaluated by JIS Z 8818: “Test method for minimum explosible concentration of combustible dusts,” IEC 61241-2-3 (1994-09) Section 3: “Method for determining minimum ignition energy in dust-air mixtures,” and JIS Z 8817: “Test method for explosion pressure and rate of pressure rise of combustible dusts.” The test are described and the results are presented and discussed.

In order to minimize environmental burden, green technologies should be important in the 21st century. High-performance catalyst layer would make significant contribution through reforming of hydrocarbon fuels, removal of toxic molecules such as CO and NH 3 from exhaust gas, reduction of nitrogen oxide (NO x ) formation in combustion, and efficient conversion of chemical energy to thermal energy in small scales. Among various kinds of catalyst support, nano-porous alumina (Al 2 O 3 ) developed with anodic oxidation of aluminum (Al) layers attracts much attention due to its extremely-large specific area, easy controllability of porosity and coating thickness, and large bond strength with the substrate. In our previous studies, we have developed a micro-scale catalytic combustor with a palladium (Pd) /nano-porous Al 2 O 3 catalyst layer, aiming at micro thermophotovoltaic power generation system, which could realize higher energy density than Li-ion batteries. In this paper, we use kinetic- and plasma-spraying for the deposition of Al, and examine the effect of the Al deposition methods on the nano-pore density. It is found that a large number of dislocations in the kinetically sprayed Al particle provide much higher nano-pore density by anodic oxidation. It is also found that nano-porous Al 2 O 3 layer kinetically sprayed and anodized has better characteristics as the catalyst support.

Effects of diffusion treatment were investigated on the interface microstructure between a Co-based self-fluxing alloy coating and a mild steel substrate to improve the adhesion strength. Diffusion treatments were carried out at 1373 K to 1418 K for 600 s to 7200 s in an Ar atmosphere. Diffusion treatment improves the metallurgical bonding at the interface due to the diffusion of Co, Cr, W, Ni, and Si from the sprayed coating layer to the substrate and that of Fe and Mn from the substrate to the coating. This mutual diffusion forms a precipitate-free diffusion layer at the interface, and the width of this layer increases in a parabolic manner as temperature and holding time increase. The apparent activation energy for the formation of precipitate-free diffusion layer was evaluated as about 360 kJ/mol. The shearing adhesion strength of the diffusion-treated coating has been remarkably improved to 200 – 400 N/mm 2 in proportion to the width of the precipitate-free diffusion layer formed along the interface, although the shearing adhesion strength of the as-sprayed coating was only 30 N/mm 2 .

This paper describes microstructure control aimed for wear-resistance improvement of Co-based (Co-Cr-W-B-Si) self-fluxing alloy coating by diffusion treatment. The diffusion treatments of thermally sprayed Co-based self-fluxing alloy coating on steel substrate were carried out at 1370K to 1450K for 600s to 6000s under an Ar gas atmosphere. Microstructural variations of the coating and the interface between the substrate and the coating were investigated in detail. A proper diffusion treatment precipitates two kinds of fine compounds in Co-based matrix. XRD and EPMA analysis revealed these precipitates to be a chromium boride dissolving cobalt and a wolfram boride containing cobalt and chromium. The size of each precipitate became larger with increasing treatment temperature and time. A coating with the proper size borides showed a superior wear-resistance.