Study On The Preparation And Properties Of Investment Casting Shell For DZ422B Directionally Solidified Blade

Although the directional solidification blade of DZ422B nickel-based superalloy used for aero-engine in China has been mass produced,there are still many quality problems in the routine production process of investment casting,which has caused some negative effects on the production cost control and production efficiency improvement.As one of the key factors in the casting process,the shell preparation directly affects the final quality of the blade.Due to many reasons(including technology blockage from foreign countries),there are still many weaknesses in our technology of shell preparation,which can not meet the requirement of investment casting for DZ422B or higher grade blade adequately,and need to be improved urgently.According to the actual manufacture of investing casting shell for DZ422B directional solidification blade,this paper focus on optimizing the process routing,building the standard operation/inspection/management procedure for each process,promoting the rapid defect diagnosis and response system,implementing total quality management and other methods to improve current shell preparation technology and also support to develop the higher technology level of shell preparation.For the purchase and acceptance of raw materials,the methods of strengthening the standard process management and promoting the standard quality inspection and control are used to assure the stable and controllable properties of shell,such as selecting the Al₂O₃ particles with wider size distribution and higher spheroidization rate,silica sol with globular particles etc.For the preparation technology of shell,this paper summarized manufacture routing design modes,made the standard operation procedure of each process(such as wax pattern fabrication,coating preparation,dipping and stuccoing,hastening drying,hot,dewaxing,preliminary calcination etc.)to promote the standardization and routinization of daily operation,and to further improve the production efficiency and qualification rate.For quality inspection and defect diagnosis of shell,total quality management method was utilized,standard inspection procedure was applied to each key production step,defect diagnosis database of feature identification,reason derivation,and corresponding actions for daily manufacture was summarized in this paper,so that it is possible to design a quality software system to elevate the efficiency and accuracy for defect solution by using computer and mobile network technology.For the research of interface reaction and scab formation mechanism between DZ422B nickel-base superalloy and Al₂O₃ shell,according to the drop morphology observation,contact angle measurement,microstructure and element distribution analysis in interface area,the interface reaction mechanism was revealed with thermodynamics basic theory and principle,and the solutions(such as superalloy composition optimization,mineralizer improvement,higher chemical stability binder(such as non-silicone content)and surface coating material invention etc.)was suggested in the paper.