高温合金叶片单晶凝固技术的新发展

DEVELOPMENT OF SINGLE CRYSTAL SOLIDIFICATION TECHNOLOGY FOR PRODUCTION OF SUPERALLOY TURBINE BLADES

分析了高温合金叶片复杂部位的凝固过程,提出了单晶组织的三维生长机制和精确制导的新理念.通过展示一系列的新发明,如导热体引晶技术、平行式加热和冷却定向凝固设备、对叶片不同部位分别进行定点冷却和定点加热的复合控制引晶技术、薄壳降升法制造单晶叶片技术等,显示了高温合金叶片单晶凝固技术发展的新思路和新举措.这些新理念的提出和新发明的实施,将有助于高温合金单晶叶片这种高精产品的制造方式实现从粗放式到精细式的根本转变.

Based on the analysis of solidification processing in complex turbine blades, a new idea of 3-dimensional and precise control of single crystal（SC） growth was proposed. A series of new techniques were presented, exhibiting the new development in the production of SC blades of superalloys. The heat conductor（HC）technique was developed to minimize the hot barrier effect which hindered the lateral SC growth. This method promotes the successful transition of SC growth from the blade body into the platform extremity prior to the nucleation of stray grains. To achieve symmetric thermal conditions for solidifying the SC blades, the PHC（parallel heating and cooling） system has been employed. With this technique, both sides of a shell mold can be both symmetrically heated in the heating zone as well as cooled in the cooling zone. The negative shadow effect in the current Bridgman process and the related defects are hence removed. With the HD（dipping and heaving） technique using thin shell, the main problems of the Bridgman process, such as the ineffective radiative heat exchange and the large thermal resistance in thick ceramic molds, can be effectively resolved. This technique enables the establishment of a high temperature gradient at solidification front. By combining targeted cooling and heating technique, a 3-dimensional control of SC growth in large components can be achieved.