Advanced Materials Research Vols. 189-193

Abstract: The microstructure analysis and hardness test were carried out on the surface of alloy nodular cast iron roll treated with CO2 laser of power 5 KW by optical microscopy, Rockwell hardometer and micro-hardometer. The results indicate the cladded layers with laser heat treatment are divided into melt region, phase change region and substrate region. The dimension and microhardness for every region are related to laser power, scanning speed and process parameters. The fatigue life of alloy nodular cast iron roll treated with laser increased remarkably.

Abstract: A new method of sheet metal forming, water jet incremental sheet metal forming (WJISMF) is presented. We give the schematic illustration of WJISMF system, which includes high pressure system, NC machine, control system, water recycle system, and some attachments, and then the virtual prototype of the system is designed. To predict the whole deformation process, some simulations are carried out. Firstly, fluid structure interaction simulation for WJISMF is performed. The water jet is modeled and simulated with a computational fluid dynamics (CFD) approach, while for the material flow in the workpiece a finite element analysis (FEA) is used. Secondly, the relationship between the workpiece material deformation and nozzle diameter, and the relationship between deformation and water pressure are presented. Thirdly, the fluid structure interaction simulation model is simplified to the structure simulation model, by adopting shell 181 element and using a pressure acting on the workpiece directly instead of the CFD model. Finally, a simulation for forming a cone box is done using the simplified model. The simulation provides a powerful rationale for the practical application of WJISMF.

Abstract: An impeller is the core of aviation engine components, the processing quality has a decisive impact on the performance of the engine. An impeller is also one of the most important basic components of centrifugal compressor. When a three-axis CNC machining centre is used for producing an impeller, great difficulties, i.e. collisions between the cutting tool and the impeller, can occur. As the surface is normally twisted in design to achieve the required performance, it can cause overcut and collision problems during machining. To solve these problems, an integrated five-axis machining approach for a centrifugal impeller by combining related machining technologies is developed. As a result, Cutter Location data based on the geometry model of blade and hub of the impeller are generated. Finally, the Cutter Location data is verified through software simulation. The results prove that the machining methodology adopted is useful and efficient.

Abstract: The present work explores an environmental friendly method for forming conversion coatings on AZ91D magnesium alloy by applying a static magnetic field. An amorphous / nanocrystalline conversion coating was developed on magnesium alloys in a phosphate-permanganate aqueous solution under a 0.5 Tesla magnetic field. The examinations of the microstructure and phase compositions reveal that the conversion coating is composed of an amorphous structure and nanocrystalline structure with mean size less than 10 nm. In a corrosive chloride solution, the amorphous/nanocrystalline conversion coating with an artificial defect were investigated by scanning vibrating electrode technique (SVET)/ scanning ion-selective electrode technique (SIET) system. The micro-electrochemical results reveal that the amorphous / nanocrystalline conversion coating as a good barrier layer can provide effective corrosion protection for AZ91D magnesium alloy.

Abstract: A low-temperature silicon pack cementation has been developed by applying direct current field (DCF) between the treated sample and the powder agents. The cross-sectional microstructures, coating thickness and high temperature oxidation resistance after siliconizing under different processes were investigated. The results show that DCF can significantly reduce the treating temperature and heating duration comparing with the conventional silicon pack cementation, the heating temperature could be lowered to 750°С from higher than 1050°С normally used. When the treating temperature was 800°С with appropriate intensity of DCF, the siliconizing coatings with thickness around 40μm was produced, while at this temperature, almost no coating could be formed by conventional silicon pack cementation，and the coating rapidly formed at lower temperature had good oxidation resistance below 700°С .

Abstract: The modification of Si-flakes from coarse acicular to fine fibrous is a common issue in Al-Si alloys casting products. The one of aims of this work is to practice the probability of applying the pulsed electric discharge (PED) to modify the morphology of Si-flakes. In the experiment, the Al-12Si alloy cast in plaster mold was treated with high voltage pulse electric discharge during the solidification. The combined effects of strong pulse electric current and chemical additives of refiner/modifier on solidification structure of eutectic silicon and tensile properties were studied. The experimental results indicated that the eutectic silicon flakes can be fragmentized by high-density pulse electric current. The best tensile properties were obtained when pulse electric discharge was used and combined with a trifle addition of refiner/modifier into the molten metal.

Abstract: This paper focuses on the influences of the technologies such as curing time, curing temperature and coating on the elastic modulus of basalt filament diaphragm fabric. This paper compares the elastic modulus of basalt filament diaphragm fabric with that of glass fiber diaphragm fabric under the same fabric density, texture and coating thickness, thus discusses the feasibility of using basalt filament as cone material. In the experiment, we use CSW-03 loom to weave basalt filament diaphragm fabric and glass fiber diaphragm fabric, then we use Werner Mathis AG LTF97885 coating machine to coat them and then use 3380Instron advanced testing machine to test the elastic modulus and the breaking strength. Conclusion: The coating curing effect, the elastic modulus and the breaking strength will reach their best when the temperature is 120°C, the time is 30 minutes. When the coating thickness is 0.05mm, the elastic modulus of basalt filament diaphragm fabric will be best. So considering the elastic modulus, basalt filament diaphragm fabric is more suitable than glass fiber diaphragm fabric. The result of this paper can be used as theoretical basis for the development of basalt filament diaphragm fabric. So we can develop more materials related to basalt filament diaphragm fabric to enhance market competitiveness.

Abstract: According to the existing insufficiency of researches of enterprise informatization level evaluation, building an evaluation model of enterprise informatization level based on grey whitenization weight cluster analysis. First, based on the existing research, build an evaluation index system of enterprise informatization level. Then, by using grey incidence analysis idea, put forward a method to determine index weight. And then, construt an evaluation model of enterprise informatization level based on grey whitenization weight cluster analysis. Finally, test the validity of the model through the application example.

Abstract: The laser cladding of Fe power technology was used to repair worn plunger piston surface. The microstructure of cladding layer, binder course and the matrix were observed by OM and SEM. Besides, the micro-hardness of different zones was measured through micro-hardness testing. The results show that the matrix metal microstructure of plunger piston is made of ferrite and austenite. By laser cladding Fe-based power on base metal, the cladding layer grain is fine and uniform, grain growth has obvious direction and finally become dendrites oriented, the microstructure of cladding layer is both second-phase hard particles and Fe-based solutes. The combination between matrix and cladding layer is smooth, belong to metallurgy bonding. The hardness of cladding layer is higher than that of other parts in three parts, the max value of micro-hardness is about 1250HV, it can agree with wear resistance need of plunge piston surface.

Abstract: It’s a simple technology to manufacture big trimming die by hardfacing on the die insert of cast iron. Here, the chemical composition, microstructure, micro-hardness, wear resistance and wear mechanism of the hardfacing layer with a newly developed electrode have been studied. The experimental results indicate that the hardfacing technology has much more advantages and cheaper than that of traditional process. The chemical composition, microstructure, micro-hardness of the hardfacing metal are all satisfied for manufacturing the big trimming die by welding on die insert of cast iron. The wear resistant test of hardfacing layers were carried out by using M2000 type tester with two different electrodes. The wear resistance of new electrode hardfacing layer is higher than that of normal hardfacing electrode D322. The wear mechanism of hardfacing layer belongs to abrasive wear model. The service life of hardfacing die insert is as long as tool steel insert which was fully heat-treated. More than 25000 workpieces can be carried out by using the hardfacing die insert. The life of repaired cold die with new kind of hardfacing electrode bar can be raised up to 30~50% than that with the electrode D322 under the same condition.