Solid State Phenomena Vol. 295

Abstract: AlN/aluminizing coating with good corrosion resistance on carbon steel was prepared by one-step powder pack method. The phase compositions were analyzed by X-Ray diffraction spectrum (XRD). The cross-sections were investigated by scanning electron microscope (SEM) equipped with an energy dispersive X-ray spectrometer (EDS). According the analysis above, the appropriate powder formula and technological parameter were determined: 40 wt.% Al + 50 wt.%Al₂O₃ + 5 wt.% NH₄Cl + 5 wt.%CeO₂, heating from 800 °C and maintaining at 900 °C for 6 hours. The corrosion resistance of specimen with AlN/aluminizing coating were measured by electrochemical test. The electrochemical measurement suggested that the corrosion resistance property of carbon steel was remarkably improved by fabricating AlN/aluminizing film. The process of pack cementation method in this fabrication is very simple, low-cost and facile, which opens a promising and effective path for industrial applications for AlN/aluminizing coating on various metallic materials.

Abstract: In this study the effect of thermal spray process on wear resistance of NiAl/Cr2C3 thermal spray coating has been investigated. For this purpose the NiAl power mixed with 10 %wt. Cr2C3 powder and milled for 1 hrs at argon atmosphere. The APS parameters such as voltage (V), current (A), spray distance (mm), powder feed rate (gr/min), were optimize using a response surface methodology. For investigation effect of spray parameters on quality of coatings, the porosity and wear resistance of coatings analyzed with SEM and pin on disk wear test. Results show that increase of voltage and current are more effective other parameters. Increasing of powder feed rate and spray distance raised porosity of coatings intensively.

Abstract: A NiCrBSi coating was produced on a pure iron plate by laser cladding technology. Electric-magnetic compound field was applied in order to improve the quality of coating. The effect of electric-magnetic compound field on the microstructure and the phase composition of coating was investigated by OM and XRD, respectively. The results indicated that the phase composition of the coatings were γ-(Fe,Ni), Cr₂₃C₆, Cr₇C₃, CrB and Ni₃B with and without electromagnetic field. Microstructural observation showed that the grains were refined obviously by electromagnetic stirring. The electromagnetic stirring could change the direction of the heat dissipation and changed the direction of the columnar crystal at the bottom of the coating. High qualitative coating without porosity were obtained under electromagnetic field.

Abstract: To further study the formation and corrosion mechanisms of AM60B vanadate films, a vanadate coating was synthesized on AM60B substrate via a chemical conversion at 50°C. The morphologies of the films and the corrosion samples were observed by using scanning electron microscopy(SEM), energy dispersive X-ray analysis(EDAX) was used to analyze the elemental distribution of the film surface and the Electrochemical Impedance Spectroscopy(EIS) and the polarization curves of the films were tested by an electrochemical workstation. The morphology of conversion film is layered structure with white balls. V element preferentially deposits near the base end and the V-rich phase is easily generated on the β-phase(Mg₁₇Al₁₂). In the course of corrosion, corrosion begins near the α-phase(Mg). During the processes of observation and analysis, the concept of micro-zone pH gradients was discovered and applied, and attempts were made to explain some observed phenomena by using this concept. The results show that the concept of pH gradients in micro zones can be used to explain the film formation and corrosion mechanisms well.

Abstract: This paper summarizes several corrosion tests and in service trials of chain with different surface conditions operated in corrosive underground mining environment of a Queensland coal mine. Galvanized chain has been employed by more and more Australian coal mines, despite the stigma against such chain formed more than a decade ago regarding susceptibility of galvanized chain to stress corrosion cracking (SCC). Trials of short lengths of galvanized links and salt spray testing were used to verify the effectiveness of the galvanized chains.

Abstract: This research is to analyze the effect of mechanical milling on the microstructure and mechanical properties of copper-iron. The sample is fabricated by compacting, milling and sintering processes. Sintering process is carried out using continuous type machine with conveyor belt mesh and the furnace type is muffle. After that, it is cooled with natural water jacket process. Vicker hardness testing and tensile strength test is performed to determine the mechanical properties of copper-iron alloys that occur. The mean value of sample 1 hardness (before milling) was 39.8 HV. The mean value of sample hardness 2 (after milling) was 74.9 HV. The value of the yield strength (σ) of sample 1 is 17.597MPa, and the value of ductility (ε) is 0.119. The value of the yield strength (σ) of sample 2 is 18.547 MPa, and the value of ductility (ε) is 0.073. The test results and analysis showed that by shrinking the size of metal powder, by milling for 2 hours, the hardness and yield strength of the product can increase. Although, the product becomes more brittle which is indicated by the decreased ductility value.

Abstract: An unalloyed ductile cast iron with a multiphase structure is designed by a novel austempering process. The designed austempering treatment consists of initial rapid quenching to 180°C after austenizing at 890°C for 20min, and finally austempering at 220°C for 240min. A multiphase structure comprising lenticular/needle-like prior martensite, fine needle bainitic ferrite and film retained austenite is obtained. The excellent mechanical properties, with a tensile strength of 1530MPa and an elongation of 3.1% can be achieved by controlling the matrix microstructure of 12% prior martensite, 15% retained austenite with 1.64% carbon content, and 73% bainitic ferrite. This is mainly attributed to prior marteniste which can promote refinement of multiphase colonies.

Abstract: The aim of this work is to study the strengthening mechanism and thermal stability of spray formed H13 steel. The microstructure and hardness of spray formed H13 steels are investigated by electron microscopy, transmission electron microscopy and hardness measurementscanning. The calculated results demonstrate that tensile strength, impact energy and hardness values of sprayed-formed H13 steel are higher than that of as-cast H13 steel when the tempering temperature is 600 °C after quenched at 1050 °C. Compared with as-cast H13 steels, tempered spray-formed H13 steels possess supernal high-temperature temper resistant stability. The chemical composition of the carbides in spray-formed steels is V and Cr rich spherical carbides are hardly influenced by the tempering treatment.

Abstract: In order to improve the cutting stability of high-efficiency micro turn-milling machine tools, avoid the chattering problem during the cutting process. In this paper, the chatter problem in the cutting process is studied based on the stable lobes. By analyzing the high-efficiency turn-milling machine tool mechanism and the turn-milling model, the micro turn-milling dynamic dynamic vibration model and the mathematical model of turn-milling chatter are obtained. Then, based on the hammer test method, the transfer function of the tool-workpiece system is obtained, and the turn-milling stable lobes of the high-efficiency micro turn-milling machine tool is constructed. Finally, the research on the stable zone of the turning main spindle parts, the turning back spindle parts and the high-frequency milling part are completed. The experimental research results guide and optimize the selection of cutting parameters for turn-milling process.