Xiao Feng Shang

Characteristics of Laser Aided Direct Metal Powder Deposition Process for Nickel-Based Superalloy

Laser additive direct deposition of metals is a new rapid manufacturing technology, which combines with computer aided design, laser cladding and rapid prototyping. The advanced technology can build fully-dense metal components directly from CAD files without a mould or tool. With this technology, a promising rapid manufacturing system called “Laser Metal Deposition Shaping (LMDS)” is being constructed and developed. Through the LMDS technology, fully-dense and near-net shaped metallic parts can be directly obtained through melting coaxially fed powder with a laser. In addition, the microstructure and mechanical properties of the as-formed samples were tested and analyzed synthetically. The results showed significant processing flexibility with the LMDS system over conventional processing capabilities was recognized, with potentially lower production cost, higher quality components, and shorter lead time.

Process Research on the Laser Rapid Manufacturing Technology

Laser additive direct deposition of metals is a new rapid manufacturing technology, which combines with computer aided design, laser cladding and rapid prototyping. The advanced technology can build fully-dense metal components directly from the information transferred from a computer file by depositing metal powders layer by layer with neither mould nor tool. Based on the theory of this technology, an experimental setup for laser rapid manufacturing process was developed. Through this state-of-the-art automated apparatus, some cladding experiments were performed to grasp the process features of laser rapid manufacturing technology. Finally, the columnar/equiaxed grain growth transition model is used to explain the morphology characteristic. Accordingly, the appropriate microstructure can be obtained by adjusting the processing parameters.

Research on Defects of Titanium Alloy Laser Rapid Forming

In the process of metal powder laser rapid forming, various defects may be caused in forming parts on account of technical parameters, equipment performance, material characteristics and other factors. While dimensional accuracy error and surface sticky powder caused by powder factor are the two major defects of forming parts. The experimental analysis finds that less or over accumulation resulting from powder feed delay is the main reason for affecting the dimensional accuracy of cladding and the main reason which affects the appearance of surface sticky powder is specific energy.

Research on Cladding Process of Metal Powder during Laser Additive Manufacturing

The process of laser additive manufacturing consists of depositing successive layers of molten metal powder to create a near-net shape. A high-power laser is used to melt incoming metal powder, which forms a molten pool on the surface. As the latter moves beneath the laser, this newly created molten pool solidifies. By properly controlling the trajectory of deposition tracks, one can create a diverse range of shapes with varying complexities. In nature, the laser additive manufacturing technology is a continuous multilayer laser cladding process under the control of computer. The microstructure morphology of cladding layer is essential for the performance of as-deposited metal parts, so the cladding process was studied through related experiment. Based on the solidification theory, the microstructure morphology and the evolution rule were comprehensively analyzed. The results indicate that the temperature gradient and the solidification rate are the primary factor determining the microstructure morphology of cladding layer.

Laser Metal Deposition Shaping System for Direct Fabrication of Parts

The fabrication of metal parts is the backbone of the modern manufacturing industry. Laser forming is the combination of five common technologies: lasers, rapid prototyping (RP), computer-aided design (CAD), computer-aided manufacturing (CAM), and powder metallurgy. The resulting process creates part by focusing an industrial laser beam on the surface of processing workpiece to create a molten pool of metal. A small stream of powdered alloy is then injected into the molten pool to build up the part gradually. By moving the laser beam back and forth and tracing out a pattern determined by a CAD, the solid metal part is fabricated line by line, one layer at a time. By this method, a material having a very fine microstructure due to rapid solidification process can be produced. In the present work, a type of direct laser deposition process, called Laser Metal Deposition Shaping (LMDS), has been employed and developed to fabricate metal parts. The LMDS apparatus consists of four primary components: energy supply system, motion control system, powder delivery system, and computer control system. These components have their specified functions, but work in association with each other.

The Effects of Nozzle and Workpiece Placements on Cooling Rate in the Vacuum High-Pressure Gas Quenching Furnace Based on CFD

Studying how and how much the factors affect on the cooling rate of workpieces is very significant to improve the ability of vacuum high pressure gas quenching furnace. From changing the structure and technology of nozzle-type vacuum high pressure gas quenching furnace, by a large number of computer simulation, this paper discusses some factors affecting the cooling rate. By changing the number and distance of nozzles on each wind pipe, we can better control the cooling rate and uniformity of workpieces. From the perspective of improved process, the number, shape, size and placement of the workpieces have certain effects on cooling rate, in which the placement of the workpiece is very significant and significant. The simulation results for the further development of new high-pressure gas quenching vacuum device provide a theoretical basis.

The Simulation of Polycrystalline Silicon Thin Film Deposition in PECVD System

Taking Silicon tetrachloride (SiCl4) and hydrogen (H2) as the reaction gas, by the method of plasma-enhanced chemical vapor deposition (PECVD), this paper simulates the deposition process of polycrystalline silicon thin film on the glass substrates in the software FLUENT. Three dimensional physical model and mathematics model of the simulated area are established. The reaction mechanism including main reaction equation and several side equations is given during the simulation process. The simulation results predict the velocity field, temperature distribution, and concentration profiles in the PECVD reactor. The simulation results show that the deposition rate of silicon distribution is even along the circumference direction, and gradually reduced along the radius direction. The deposition rate is about 0.005kg/(m2•s) at the center. The simulated result is basically consistent with the practical one. It means that numerical simulation method to predict deposition process is feasible and the results are reliable in PECVD system.

Realtime Measurement of Temperature Field during Direct Laser Deposition Shaping

Direct laser deposition shaping is a state-of-the-art rapid prototyping technology. It can directly fabricate metal parts layer-by-layer without any die, mold, fixture and intermediate, just driven by the laminated CAD model. Accordingly, how to improve the quality of as-formed parts becomes an urgent issue in this research field. It is well known that as for the hot working, the heat history can generate enormous influence on the microstructure and mechanical properties of the parts. Due to the large quantity of heat introduced by laser fabrication process, it is necessary to build a temperature measuring platform to realtime monitor and control the temperature field in the laser fabrication process. As a result, such platform was created to communicate with computer by the temperature data collecting module and interface standard converting module, and achieved the temperature acquisition in the serial communication process through the Microsoft programming software. The experimental result proves the validity of the platform, which can provide effective boundary condition and experimental verification for the numerical simulation. In addition, the desirable temperature distribution can be obtained through the realtime process monitoring and effective parameter adjusting.

Evaluation of the Stability and Precision of Powder Delivery during Laser Additive Manufacturing

The fabrication of metal parts is the backbone of the modern manufacturing industry. Laser forming is combination of five common technologies: lasers, rapid prototyping (RP), computer-aided design (CAD), computer-aided manufacturing (CAM), and powder metallurgy. The resulting process creates part by focusing an industrial laser beam on the surface of processing work piece to create a molten pool of metal. A small stream of powdered alloy is then injected into the molten pool to build up the part gradually. By moving the laser beam back and forth and tracing out a pattern determined by a CAD, the solid metal part is fabricated line by line, one layer at a time. By this method, a material having a very fine microstructure due to rapid solidification process can be produced. In the present work, a type of direct laser deposition process, called Laser Metal Deposition Shaping (LMDS), has been employed and developed to fabricate metal parts. In the LMDS process, the powder delivery system is an important component to perform the powder transport from powder storage box to powder nozzle, which supplies the raw material for the as-deposited metal parts. Consequently, the stability and precision of powder delivery during LMDS is essential to achieve the metal parts with high quality, so it is critical to evaluate the main factors closely related to the stability and precision of powder delivery. The shielding gas flow and the powder feeding rate were ascertained through experimental measure and formula calculation. The results prove that the suitable shielding gas flow and powder feeding rate can promote the stability and precision of powder delivery, which is the basis for the fabrication of as-deposited metal parts with flying colors.

Sliding Sleeve Fracturing Strength Analysis of the Ball Based on Ansys Workbench

In the oilfield development, the packer is one of important downhole tool in oilfield drilling technology, and sealing effect of the sliding sleeve fracturing ball system directly affect the packers sealing performance. Using UG software to establish 3D sliding sleeve fracturing ball and base model. Based on Ansys workbench simulation platform, finite element analysis was carried out on the sliding sleeve fracturing ball, distribution pattern in different materials, and sealing effect. Fracturing experiments were done to verify the accuracy of the simulation analysis and ensure the sliding sleeve fracturing system reliability in practical work.