Narrow Results

Electron beam physical vapor deposition (EBPVD) is being used in coating components for many applications such as for producing nanostructures and integrated circuits (ICs) coating in electronic industry. In this work, copper was deposited on the SiO₂/p-type Si(100). Thin film characteristics are investigated by scanning electron microscopy and X-ray diffraction (XRD). Then oxidation behavior of deposits was evaluated by Dektak Surface Profiler and weight gain method at 200 and 300°C. Results showed that thin film copper deposited by EBPVD has better oxidation characteristics in comparison with copper foil.

Two types of WC–12Co coatings with different modifications were deposited on steel substrates using high velocity oxygen fuel (HVOF) spraying. The coated samples were oxidized at 550${}^{\circ }$C and 650${}^{\circ }$C in ambient atmosphere. Oxidation mass gain was measured by electronic balance. Phase composition and microstructure evolution of both coatings after oxidation were conducted by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Microhardness testing was performed before and after oxidation testing. The results showed that at 550${}^{\circ }$C and 650${}^{\circ }$C, the rare-earth modified WC–12Co coating has lower oxidation rates compared with the nanostructured WC–12Co coating. This might be due to the rare-earth modification coating reducing the porosity and oxygen diffusion in the coatings, therefore delaying the crack formation and propagation.

In this study, we focus on the oxidation behavior of the oxide scale with Platinum (Pt) on free standing NiCoCrAlY coating in air with water vapor at high temperature. The Pt layer is deposited on the NiCoCrAlY coating surface by electroplating, and then heat treatment at 1000${}^{\circ }$C with Argon (Ar) protection. Cycle oxidation of the oxide scale with Pt is conducted in air and air with water vapor at 1050${}^{\circ }$C. The results indicated that the spinels (NiCr₂O₄) are formed on the surface of the alumina scale in air and air with water vapor. However, this kind of spinel is inhibited in the air with water vapor and the scale on the coatings with Pt presents a good adherence during oxidation process. The thermal stress and crack initiation and propagation will be discussed.

The oxidation behaviour of Ni8Al and Ni25Cr coatings produced by high velocity oxygen fuel spray (HVOF) which were deposited on Fe-based alloys (CB2) was investigated. We simulated the service environment of the steam generator unit, and put the samples in a thermostatic tube furnace at 650${}^{\circ }$ in air with 20 wt.% water vapor for 1000 hours of cyclic oxidation. The formation mechanism are explained using SEM, XRD, and EDX. There were no spallations and obvious cracks in both coatings. Ni25Cr coating generated a better protection oxides scale than that scale on Ni8Al. The behavior and mechanism of the oxide scale formation had an important influence in coatings and we have discussed these phenomenons in the study.

In this paper, high temperature oxidation behavior and surface morphology evolution of galvannealed (GA) coating during heating and dwell stages were studied. The variations of chemical compositions and thickness of oxide layer with time were analyzed. In addition, the influence of austenization temperature on integrity of oxide layer was discussed. The results showed that the oxide layer on GA coating was mainly composed of ZnO. During austenization treatment, the morphology of surface oxides underwent a transition procedure from particles to clusters and finally to a compact layer. In addition, the thickness of oxide layer did not increase significantly during dwell stage. Furthermore, the austenization temperature should not exceed 900 °C to avoid rupture of the oxide layer and suppress zinc loss in the coating.

In this paper, the NiCoCrAlY/BaF2/CaF2/C/Y composite coating prepared by plasma spraying of high temperature oxidation behavior is researched ,which is combined effect of heat and friction environment, as well as simple static study on both the high temperature environment. Results showed that: in high temperature friction environment, coating is oxidized more seriously than simple static oxidation; Degree of coating oxidation under 500°C is lower than 800°C, and oxidized coating will produced peeling in friction process; The state of oxidized film on coating surface is different with friction processing, which with no full of lubrication film, lubrication film alternating appeared, full of lubrication film and variety complex of situation.