Advanced Materials Research Vols. 291-294

Abstract: In the paper, it is introduced a new method of non-abrasive cryogenic polishing which is used to polish GaAs chips. It is also analyzed the influence of different factors on polishing surfaces and polishing uniformity. The rotate speed of work piece disk is a more important factor on impacting the polishing uniformity than offset e.

Abstract: In this paper the influence of snorkel length and snorkel inner diameter and lifting gas flow rate on inclusion removal rate are discussed. It is found that inclusion removal rate varies greatly with snorkel length and snorkel inner diameter. Prolonging the snorkel length is benefited for inclusions removal in RH and inclusion remove time is enhanced, but inclusion remove rate is decreased when snorkel inner diameter is reduced. There is a best lifting gas flow rate for inclusion removal.

Abstract: Two silane-based hybrid coatings were developed to modify the surface energy of phenolic resin impregnated paper. The coated paper samples were further pressed onto surfaces of plywood. The surface properties and water repellence of coated paper were investigated by AFM, XPS and water contact angle measurements. The water absorption of plywood with pressed paper was studied by water uptake tests. It was found that the sol-gel coatings had slightly improved the water repellence of the impregnated paper. The water absorption of plywood was also slightly decreased.

Abstract: The acid resistance of ultramarine blue was greatly enhanced by silica coatings. Sodium metasilicate nonahydrate was used as silica precursor and ammonium chloride was used to react with it. Fourier transform infrared (FT-IR) spectroscopy was used to characterize surface structure on the coating layer. The effects of coating conditions on acid resistances of the coated ultramarine blue were investigated. The acid resistance was evaluated by immersing the pigment in 10 wt% hydrochloric acid. The results showed the optimal mass ratio of silicate to ultramarine was 3.75 and the proper solid content was 60 g/L. Under above conditions, the silica coated ultramarine blue exhibited an acid resistance of 8, while the uncoated ultramarine blue only showed an acid resistance of 1.

Abstract: Fe-Cr-Ti-C composite powder was prepared by precursor carbonization-composition process using the mixture of ferrotitanium, chromium, iron powders and precursor sucrose as raw materials. In situ synthesized TiC particle reinforced composite coating was fabricated on substrate of Q235 steel by reactive plasma cladding process using Fe-Cr-Ti-C composite powder. Microstructure of the coating was observed by scanning electron microscope (SEM), the phases in the coating were determined by X-ray diffraction (XRD), and the wear resistance of the composite coating was evaluated under dry sliding wear test conditions at room temperature. Results indicate that the composite coating consists of in-situ the reinforcing TiC carbide, (Cr,Fe)₇C₃ eutectics and austenitic, and is metallurgically bonded to the Q235 steel substrate. TiC carbide in the composite coating showed the gradient distribution. TiC particles present granular in the fusion zone and central zone, and present dendritic in the surface of the composite coating. Hardness of the coating from surface to fusion zone is little difference, the average hardness of the coating is about HV_0.2750, is as 3.2 times as the base. The wear mass loss of Q235 base material is 12 times as that of the composite coating.

Abstract: Considering the concave cone 3 dimension interface topography unit, the distribution of residual stress in thermal barrier coating was calculated using ABAQUS soft by finite element method. The calculating result shows that the residual stress is affected by interface topography unit obviously. Compressive stress exists in concave cone topography unit. Stress concentrates in boundary of topography unit and reaches maximal value at the lowest place of the topography. Compressive stress changes with the size of topography unit and the space between two topography units distinctly.

Abstract: Wear-resistant casting was made by V-EPC infiltration process. The matrix material was high boron steel casting. Surface composite materials layer was ceramic particles, such as WC, Ferrochromium, and Borax, etc. High boron molten metal was infiltrated into the composite layer and a good cast-infiltration layer may be formed by the interaction of vacuum and high temperature. The wear-resistant casting made with this process has high strength, hardness, and good wear-resistance. It is a new process that wear-resistant casting will be made of.

Abstract: Cr-Al-N coatings with the thickness of about 2 mm have been prepared in a magnetron sputtering system by reactive co-sputtering from a chromium target and an aluminum target in a mixed Ar/N₂ atmosphere. The effects of substrate negative bias voltage (VB) on the microstructure and critical failure load have been investigated by a scratch test as the VB varied from 0 to –150 V. The critical failure load reached the maximum value for the coating deposited under VB = –50 V, then decreased with VB further increasing. Re-sputter effect of The heavy bombardment of the ion to the substrate improve the critical failure load for the coating deposited under VB = –50 V. The decrease of the critical failure loads for the coatings deposited under –100V and –150 V probably resulted from the high microstrain in the crystal lattice.

Abstract: Samples of CeO₂-WC- Ni base alloy coating were made on 45# steel substrate by vacuum melting. The influence of CeO₂ addition on microstructure of longitudinal section of coatings, elements diffusion at the junction, and WC morphology and distribution was analyzed by scanning electron microscopy and energy dispersive spectroscopy. The results showed as follows: with 0.75% CeO₂ addition, the coating best combined with the substrate and had least pores, cracks and other defects; CeO₂ played a significant role in promoting the diffusion of alloying elements (mainly Fe, Ni diffusion at the junction); CeO₂ changed the morphology and distribution of WC hard phase in the coating, making it small, uniform, and dispersed, and promoting the diffusion between Ni-based alloy and WC in the coating.

Abstract: Superfine coatings have been prepared by Electro-spark deposition (ESD) on die steel substrate with WC-8Co electrode. The microstructures and abrasion performance of the coating were investigated by X-ray diffractometer (XRD), scanning electron microscopy (SEM) and microhardness tester. The results show that ultra-fine particles prevail in the coating. The primary phases of the coating contain Fe₃W₃C, Co₃W₃C, Fe₇W₆ and W₂C. The maximum microhardness reaches 1432.5 HV0.3. The results of abrasive test demonstrated that the coating had an excellent sliding wear resistance because the superfine particles distributed dispersedly in the coating increased the resistance to micro-cutting and plowing during the wear test, which effectively improves the surface performance of die steel substrate.