Wangping Wu

Oxidation behavior of multilayer iridium coating on niobium substrate

In this study, a multilayer iridium coating was processed on niobium substrate by double glow plasma technology. The coating was ablated under an oxyacetylene flame at a temperature up to 2000°C. The oxidation behavior and the failure mechanism of the ablated coating were investigated. The surface and fracture surface morphology were examined by means of scanning electron microscopy. The phase composition was identified by X-ray diffraction. The element analysis was determined by energy dispersive spectroscopy. The results show that many micropores were present on fracture surface and surface. The porosities on the surface of multilayer and monolayer after ablation were about 0.55% and 2%, respectively. The niobium substrate ignited to form masses of gaseous oxide under an oxyacetylene flame. The multilayer iridium coating for protecting niobium substrate from ablation was deteriorated due to effects of the underdense coating, volatile gas and interdiffusion between the coating and the substrate.

EFFECT OF ZrO2 POWDERS ON THE PYROLYSIS OF POLYCARBOSILANES COATING UNDER LASER ABLATION

Aircrafts hold the outstanding mastery of the sky in modern wars, however the laser beam weapons can carry out laser attacking to aircrafts. The purpose of the present paper is to research on a new type laser protective material. Polycarbosilanes (PCS)/divinylbenzene mixtures containing ZrO2 powders were brushed to the surface of the aluminum alloy plates and then cured at 150°C for 6 h. The PCS-coated plates were ablated by laser for 3 s. The phase identification of as-ablated powders was examined by X-ray diffraction. The results indicated that the as-ablated powders of cured PCS were composed of major phase β-SiC and smaller amounts of free carbon. The PCS composite coating played a certain role of laser ablation resistance. The effect of added ZrO2 powders on the pyrolysis of PCS-coating under laser ablation is conspicuous.

Influence of Irradiation Time on Laser Ablation Behavior of Polycarbosilanes Coating

Aircrafts hold the outstanding mastery of the sky in modern wars. However, the laser beam weapons can carry out laser attacking to aircrafts. The present paper proposes a new type of coating of laser resistance. Polycarbosilanes (PCS)/divinylbenzene mixtures were brushed to the surface of the Al alloy plates and then cured at 150°C for 6h. The PCS-coated plates were ablated by 1kW laser beam for 1s, 3s, 5s, and 10s. The phase identification of the as-ablated powders was examined by X-ray diffraction. The ablation degree was evaluated by testing the volume change. The results indicated the PCS coating played a certain role in protecting the Al alloy plates by absorbing the laser energy. The residual powders after ablation were composed of major phase β-SiC and smaller amounts of free carbon. Although PCS coating was destroyed while 10s irradiation time, the Al alloy plate was protected. The ablated volume of the coating was consistent with the irradiation time according to a multinomial equation.

Mechanical and electrochemical properties of platinum coating by double glow plasma on titanium alloy substrate

In this paper, a platinum coating was deposited on titanium alloy substrate by a double glow plasma. Phase and microstructure of platinum coating were examined by X-ray diffraction and scanning electron microscopy, respectively. The microhardness of the coating was estimated by nanoindentation instrument. The adhesive force between the coating and the substrate was performed with scratch tester. The electrochemical behavior of the platinum coating in 3.5 wt % sodium chloride solution was investigated by potentiodynamic polarization. The results indicated that an adherent platinum coating could be successfully obtained on titanium alloy substrates. Compared with the titanium alloy substrate, the platinum coating had a relative low corrosion current density and high corrosion potential. It indicated that the platinum coating had a better corrosion resistance than the titanium alloy substrate.