Selection and optimization of chemical and fractional composition of the collapsible core for hollow blades

Increasing the requirements for cast cooled GTE blades and the complication of their internal design necessitates the search for new compositions of the core masses with higher strength and resistance to thermal shocks, chemical inertness to high-temperature alloys, low coefficient of thermal expansion and high accuracy of geometric dimensions. On the basis of patent studies, a new chemical composition of the core sand mixture is theoretically justified and proposed. In order to optimize the fractional composition of the core sand mixture, an analysis was made of the methods for packing polydisperse particles in composite materials. From which it follows that most of the methods considered have a theoretical orientation, and the proposed design formulas that are used in the manufacture of technical ceramics, concretes and asphalts can not be uniquely used in the manufacture of cores. They do not take into account the distinctive features of the formation of the fractional composition of the cores. A feature of the structure of the core is the presence of carcass-forming fractions. They form the structure of the rod, directly touching each other in a geometrically correct order. These fractions depend on dimensional stability, propensity to shrink and warp the core, the maximum possible volume fraction of the dispersed phase. As a result of the developed technique, a dimensional sequence of the fractional composition of the powders was chosen and the chemical and fractional composition of the core sand mixture was optimized by the calculation method. Investigations of the physical and mechanical properties of samples made from a new core sand mixture showed that they have higher properties, less tendency to warping, shrinkage, and a lower coefficient of thermal expansion than the standard composition. From the experimental core sand mixture, cores for hollow blades were produced, which produced positive results. Defect in warping, breaking the core is reduced more than 2 times. The use of the mixture makes it possible to increase the ultimate strength of the cores during bending to σ = 24-26 MPa. Reduce the linear shrinkage to 0.1-0.2% and the depth of interaction with the alloy ZHS6U to 0.04-0.06 mm. A new core composition with an optimized chemical and fractional composition was tested and recommended for serial production.