Liangbing Wang

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.

Ablation Morphology and Microstructure of 3D Orthogonal Cf/SiC Composites Prepared by PIP

SiC ceramic matrix composites reinforced by 3D orthogonal carbon fibers (C/SiC) were prepared by polycarbosilane infiltration pyrolysis (PIP). The 3D C/SiC composite was ablated by oxy-acetylene flame. The oxygen volume flow and acetylene volume flow were 0.42 L/s and 0.31 L/s, respectively. The ablation period was 180s. The ablation morphology and microstructure of the surface of 3D C/SiC composite were investigated. The ablation mechanism of the 3D C/SiC composites under the oxyacetylene condition is a combination effect of thermo-oxidation ablation, thermo-physics ablation and mechanical erosion.