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.

Nano-dispersed α-Al 2 O 3 /YAG composite coatings were successfully obtained by plasma spraying of the granulated Al 2 O 3 /Y 2 O 3 powder, and the post heat treatment. The as-sprayed coating was composed of an amorphous phase, metastable Y-Al-O solid solution. After the heat treatment around 1473K, two crystalline phases, α-Al 2 O 3 and YAG, precipitated, so that the fine dispersed Al 2 O 3 /YAG composite coatings were formed. The sizes of the precipitates could be widely controlled by time and temperature of the heat treatment. Hardness and wear property were evaluated in this nano-structured CMC coating.

The Thermal Barrier Coating (TBC) used to improve the heat barrier and wear resistant property in high temperature of the aircraft engine and the automobile engine, usually has a two layer structure. One is a ceramic top layer for heat insulation and the other is a metal bond layer to facilitate the bond strength between the top ceramic layer and the substrate. But, the coated layers can be peeled off because of the accumulation of the thermal stress by the difference of the thermal expansion coefficient between metal and ceramics in a heat cyclic environment. In this study, the intermediate layer produced by plasma spray process was introduced to reduce the thermal stress. The powders of plasma spray coating were Yttria Stabilized Zirconia (YSZ), Magnesia Stabilized Zirconia (MSZ) and NiCrAIY. The intermediate layer was sprayed with the powders of partially stabilized zirconia with 50wt% NiCrAIY between the ceramics top coat and the bond coat for the purpose of alleviating heat expansion. The high temperature wear and thermal shock test were conducted. The high temperature wear resistance of the YSZ TBC was better than that of the MSZ TBC. The wear resistance decreased with increasing temperature between 400°C to 600°C. The 3 layers TBC with YSZ top coating showed the best thermal shock resistance. This means that the intermediate layer played an important roll to alleviate the difference of the thermal expansion between metallic layer and ceramics layer. SEM and OM were examined. The bond strength, hardness test, and wear test were also studied.