Papers by Author: Yong Hong Fu

Abstract: The vanadium carbide (V₈C₇) coating was fabricated by in situ reaction which used gray cast iron and vanadium plate as raw materials providing carbon and vanadium sources, respectively. The microstructure, phases, and adhesion strength of V₈C₇ coating were investigated by scanning electron microscope (SEM), X-ray diffraction (XRD) and a single scratch test. The XRD results showed that the coating consisted of V₈C₇ and α-Fe, with the peaks of (222), (400), (440), (622) and (444) of V₈C₇ phase were confirmed. Moreover, the average diameter (D) of the V₈C₇ particles in the range of 432~582nm was calculated on the basis of the Scherrer and Halder-Wagner equations. The critical load of interface between V₈C₇ and substrate was 98.3 N, which implied that the interface of V₈C₇ coating /substrate had excellent adhesion strength.

Abstract: Tungsten carbide (WC) reinforced Fe-matrix surface composites were prepared by in-situ synthesis between tungsten plate and graphite in grey cast iron. The microstructure, fracture toughness, and fracture of the WC layer were investigated by scanning electron microscope (SEM), X-ray diffraction (XRD) and the Vickers indentation technique, respectively. The results revealed that heat treated at 1125°C for 135min in argon atmosphere the main phase was WC with a bit of α-Fe. The fracture toughness (K_IC) of the WC layer calculated using the Niihara’s equation, was 5.21 MPa·m^1/2. Fractographic observations revealed that cracks propagated along the grain boundary under 2 kg loads. Moreover, both the WC particles and the interface between the WC layer and the matrix had a strong bonding strength.

Abstract: In order to predict the geometry character of laser surface micro-texturing, the finite element analyzing software ANSYS is used to simulate temperature field and crater on the laser ablation. The influence and change regulation of laser intensity, laser pulse number and pulse duration in laser surface texturing are analyzed in detail. The simulation results conclude the best laser intensity in laser-pulse and materials interactions on certain conditions, and the best pulse duration in nanosecond laser micromachining. This research establishes the foundation for laser machining regular non-smooth surface in a rapid and effective way.

Abstract: The laser honing technique is a new surface texturing technique. As the piston ring at the top or lower oil attachment point works under worse lubrication condition, its wear increases severely, laser texturing was used to the piston ring/liner, lineary extending grooves and regular arranged dimples with predetermined parameters was well-matched with the needs of lubrication. The effects of different dimple shapes, such as sphere coronal, combined sphere coronal ,columnar, hexahedral, and trapezoidal dimples was analyzed by the theory of hydrodynamic lubrication. It was deduced that trapezoidal dimples are fit for only single running orientation and sphere coronal and combined sphere coronal dimples are fit for double running orientations. The experimental researches show that laser texturing not only can reduce the oil consumption and the cost of engine but also can prolong its work life.