Basic Study On The Technology Of Plasma-Spray Forming Parts

PSFP (Plasma Spray Forming Parts) is a new technology of forming parts, which uses plasma jet as heat source and makes the selected powders deposited on the surface of prepared prototype under specific technical conditions. By means of backing, removal prototype and hardening treatment, the functional parts or cavities can be obtained. After synthesized recent results of plasma processing, rapid prototype manufacturing, material engineering and other research fields, PSFP is put forward. PSFP is put forward in accordance with some difficult problems existing in manufacturing industry for a long time also. It uses the complementation of plasma spraying and RP reasonably. It is suitable for making parts of ceramic, composites, metal and alloy with high melting point and high hardness, especially for making some ceramic thin shells with special shapes. The object of this thesis is how to get high quality parts. The basic regularity and some key technique problems to the PSFP technology are systematically studied, and the basic theory of PSFP is fundamentally built up, also more stable technological standard is obtained. By means of schlieren method, experiments and analog- data technique, the phenomena and data in the process of PSFP are comprehensively observed, recorded, and analyzed. The dynamics and thermophysics characteristics of plasma jetand the powder in it are revealed. Also the impact ofcharacteristics mentioned above on the precision, propertyand microscopic structure are studied. The models set up areconformed to the results of experiments. All the experimentsand models are useful for improving the quality of partsformed.The PSFP technique like separating prototype is suggestedand adopted, and in result the parts in ceramics and ceramicscomposite with high dupIicate precision are successfullyobtained while cannot easily be obtained by normal ways. Thetechnique of separating prototype and the surface treatment ofprototype adapted to prototype material, spray material andparts' structure is emphasized.For the first time, the water-soluble-prototype PSFP isproposed and adopted. The thin shells in metal, nonmetal andcomposite are successfully obtained. The result shows thatwater-soluble-prototype PSFP is one of the destroyingprototype PSFP, which has an excellent prospect, as it iseconomical and safety.To overcome the air pollution of the spray powder andprototype and to reduce the content of oxide in the partsobtained, the PSFP experiment with protection nozzle iscarried out, and in it G3l4 alloy powder is taken as anexample. In order to reduce the porosity of the parts fOrmedand to get high-density parts, some measures are taken toimprove the speed of plasma jet and the melting powder.Taking KF-l2 (WC-Co) powder as an example, the PSFPexperiment with speed up nozzle is conducted. The results ofall these tests show that if the measures mentioned above istaken, the quality of the plasma jet can be improved, thenproceed to improve the quality of the parts. All the measuresare simple, workable and effective.To make further improvement on the quality and themechanical property of the parts, the techniques such aschemical plating, vacuum impregnation and laser melting toharden the parts obtained by PSFP are adopted. Also themeasures like chemical plating and blackening process aretaken to improve the corrosion resistance of the pieces fOrmedby PSFP with Fe-based alloy powder. By analyzing of theoryand studying on the experiments, the optimized technologicalstandard is obtained, and the applied foundation of PSFP hasbeen laid.The techniques of rapid manufacturing mould and makingsome special shaped thin shells (the shells can b...