On the question of porosity of aluminum castings obtained by injection molding

Abstract

The constantly accelerating pace of life and the rapid growth of industry inevitably lead to an increase and toughening of requirements for manufactured products. Therefore, the scope of application of special methods for obtaining blanks is expanding, among which one of the leading places is occupied by the injection molding method (IMM). The advantages of the IMM include, first of all, high productivity and dimensional accuracy of castings, the minimum need for mechanical processing, the possibility of obtaining castings with a complex external configuration, as well as the automation of the process. The main disadvantages are the high cost of molds, as well as the insufficient quality of the resulting castings, primarily the gas subsurface porosity and gas roughness. In most cases, the IMM is used to obtain castings from zinc, copper and aluminum alloys. The most widespread are aluminum alloys, which make it possible to manufacture castings with different properties depending on the alloy grade. For most grades of aluminum alloys, disadvantages associated with sufficiently high melting temperatures and chemical activity when interacting with the mold are inherent. All these factors make the IMM a complex technological process, for which the challenge of insufficient quality of the resulting castings is urgent. Traditionally, this issue is solved by choosing the technological modes of the casting process. However, in some cases, it is very difficult to achieve high quality castings only by selecting technological modes. The authors have proposed an universal method for improving the quality of castings by applying the developed protective coatings on forming surfaces of molds by cathode-ion bombardment (CIB). The paper presents the results of experimental studies proving the effectiveness of the use of wear-resistant coatings obtained by the CIB method of various compositions in comparison with the traditionally used nitriding in terms of gas and surface porosity, as well as the roughness of castings. The economic substantiation of the efficiency of the use of CIB coatings in comparison with nitriding is presented.