Papers by Keyword: Vacuum Melting

Abstract: In order to study the effect of tantalum to the microstructure and phase composition of Co-8.8Al-9.8W-XTa (X=0,2,at%) superalloy. The Co-8.8Al-9.8W-XTa (X=0,2) supperalloy used pure element powder, according to the ratio of different atomic percentage composition to make ingredients. It is mixed by planetary ball mill, pressed into blocks after the melting shape. Vacuum induction melting process was prepared by melting, after grinding, polishing, and after a volume of 5% perchloric acid and 95% of the electrolytic etching solution prepared in ethanol corrosion observed after analysis of the microstructure and phase composition by OM and XRD analysis. It can be found that the 9.8W and 2Ta alloy were mainly composed of rich γ-Co matrix of austenite precipitation of γ phase and coherent with matrix of the L1₂ structure of γ′-Co₃(Al,W) phase. In addition, Ta element has effect on grain refinement and the number of γ′-Co₃(Al,W) phase refines grain.

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: The effect of melt-casting temperature on the microstructure and properties of transition interlayer for CuNiMnFe/30CrMnSi material was investigated in vacuum condition. The results show that the thickness of the transition layer and its bond strength increase, and then decrease with increasing temperature. At 1130 , the intermediate transition layer has the largest width, which is 132μm, and the tensile strength can reach up to 1322Mpa. In the intermediate transition layer, mutual diffusion occurs among these alloying elements. These elements, such as Cu, Ni and Mn, diffuse into 30CrMnSi and results in the formation of Fe base solid solution, and no harmful brittle phases are produced in the proximity of bonding interface, thus it has a good metallurgical bonding for the two materials.

Abstract: Electron beam cold hearth melting process is an efficient method to produce the premium quality titanium alloys, especially to eliminate inclusions. A simulation work was carried out to study the process, concerning the flow field and particle trajectory at three different melt rates. The simulation results show that, when there is an overheat zone near the outlet zone, the molten metal flows to the sidewall of the cold hearth, and from the outlet zone to the inlet zone at the top surface which avoids the inclusion particle flows out the cold hearth. At the bottom of the liquid pool, the fluid flows to the outlet directly along the center plan, which forms a short circuit, decreases the residence time of the inclusion particles; there is a critical density range of inclusion particles, which have more probability to flow out of the cold hearth. The inclusion particles, whose density lower than it, will flow to the sidewall. The inclusion particles, whose density higher than it, will sink into the bottom mushy zone. Both cases let the inclusion have higher probability to eliminate the inclusions.

Abstract: Rare earth was added in foundry magnesium alloy in vacuum melting. Analysis and measurement showed that the quantity of inclusions was decreased and the mechanical properties were improved. The size of crystal grain was decreased by 59%, the yield strength was increased by 38% and elongation percentage was increased more than 7 times. On the basis of this experiment, the approaches of improving the mechanical properties of magnesium alloy were brought up.