Refining melts of heat-resistant alloys during casting of GTE details in shell forms obtained by foamed polystyrene models

Abstract

Minimization of the melt contamination of heat-resistant alloys from excess gas content, non-metallic inclusions during crystallization upon receipt of the GTE details conducted by the authors empirical choice an of thermal conditions and technical parameters of foam ceramic filters (porosity, thickness, pore diameter) during in-molding. The use of more chemically and thermally stable refractory cast ceramics (filters, molds, crucibles), developed with the participation of the authors, also prevents contamination of the melt with impurity elements. Thus, the total volume content,%, of non-metallic inclusions decreased by 1.3 – 1.6 times, the mass fraction of gases, (oxygen, hydrogen, nitrogen)%, in castings, decreased by 1.5 – 2.0 times for both types of alloys. Tested by the authors in the manufacture of molds replacement of the lost wax casting method on the burned expanded polystyrene models, allows to prevent the possible deformation of low-melting wax-containing model for sufficiently large parts and to reduce part defects in dimensional accuracy and improve surface cleanliness. In general, the authors proposed the integrated use of in-house filtration refining of melts when casting in shell molds, made by combined technology using polystyrene foam and wax-containing models, this made it possible to obtain complex profile parts with a high range of performance characteristics by optimizing structural components when refining the melt from non-metallic inclusions and gases. Thus, the tensile strength at the test temperature of 900 °C and elongation increased from 650 to 690 MPa and from 9 to 14 %, respectively, for CM104 – VI + (Ta + Re) alloy, and from 750 to 780 MPa and from 15 to 19%, respectively, for the alloy CM88Y + (Ta + Re).

Keywords

• superalloys
• refining
• foam-ceramic filter
• expanded polystyrene models
• shell forms