Kazan National Research Technical University named after A. N. Tupolev — КAI, Kazan, Russia:

R. V. Gavariev, Senior Lecturer of a Chair “Design-Technological Supplying of Machine-Building Productions”, e-mail: Gavarievr@mail.ru
I. A. Savin, Assistant Professor, Head of a Chair “Design-Technological Supplying of Machine-Building Productions”

Nizhny Novgorod State Technical University, Nizhny Novgorod, Russia:
I. O. Leushin, Professor, Head of a Chair “Metallurgical Technologies and Equipment”

The problem of service durability of the injection molds for zinc alloys pressure casting was examined. Differences between pressure casting of aluminum and zinc alloys are assigned. Key factors affecting damages of the shape-generating surfaces are considered, including the ones caused by power and temperature influences. It is determined that the greatest negative impact is caused by tensile stresses resulting in arising of new cracks and growth of already existing ones. It is indicated the need of making the additional compression stresses to compensate the tensile stresses impact. These conditions are met by the proposed method of the molds’ durability increase, based on the solid multifunctional coverings put by cathode-ion bombardment. The principal advantage of the above mentioned coverings is substantiated by the fact that the positive properties of the single layer are not changed when it is used in a multi-layer structure. There are also determined the key characteristics of nitration presenting the most common way of increasing the service durability of the shape-generating surfaces. The experimental data in support of the proposed theoretical hypothesis are cited. According to these data, the use of multilayer coating put by cathode-ion bombardment allows to increase the quality of the obtained castings in a porosity parameter. Moreover, the service durability indicator of the inserts with a multilayer coating is increased by 25% as compared with the nitration ones and makes about 200 000 cycles of press fittings.

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