Influence of compression modes of waxy powders on stress-strain state of compacts used in precision casting

The high demands placed on the surface quality and geometric complexity of metal products, structures and parts produced from a wide range of non-ferrous and ferrous alloys determine the demand for investment casting as a method that provides a range of critical products for the needs of aircraft, ship building and mechanical engineering industries. A number of “bottlenecks” in the implementation of investment casting processes include a significant number of technological operations, each of them is accompanied by phenomena of a thermophysical nature that require correction, and it ultimately determines the high cost of casting. The difficulties arise from phenomena such as shrinkage of the pattern material, its thermal expansion during melting from a ceramic mold, which determines penetration of pattern mass into ceramic pores and can affect the appea­rance of surface defects, the chemical composition and structure of the alloy of future casting. The process of forming a porous surface on wax patterns without shrinkage defects by pressing powders of waxy materials is aimed at eliminating the noted shortcomings, which ensures the required geometry of the compacts and absence of deformation effects on ceramics of the model material at the stage of its melting. Widespread use of the method is hampered by the lack of information about the features of stress control in the compact body determining the magnitude of elastic response of the compacted material, which is an order of magnitude less than thermal shrinkage. The paper presents the results of an experimental study of influence of the compression rate of powder materials on the stress-strain state of pressed wax patterns formed in a closed matrix, as well as on the strength of these compacts.