Yurii P. Borodii, Cand. Sc. (Eng.), Assoc. Prof.

National Technical University of Ukraine "Igor Sikorsky Kyiv Polytechnic Institute"

Research and Technology Equipment With Creation
Hardfacing on Parts of Bodies of Rotation Type

More efficient use of modern technology in various industries can achieve continuation of its operational lifetime by surface hardening of working surfaces, as well as its fast and high-quality repair and restoration parts. Considerable interest for the practice of electro-spark alloying (ESA), which belongs to the group of electro methods of surface hardening of machine parts. The main advantages of the method is the ability to transfer to the surface of the treated materials of high hardness (carbide) in the high strength of adhesion layer reinforced with a base coating without significant deformation of the parts. A significant effect can be achieved using the combined technology of strengthening of machine parts with a combination of ESA and surface plastic deformation (SPD). With the combined strengthening is possible to create multi-layered wear-resistant coatings on working surfaces of machine parts. At the same time manages to largely overcome the disadvantages of each method to strengthen and control the properties of the coating.

We investigated methods of application-layer coatings:

1. Electro-spark alloying (ESA).

2. Surface plastic deformation (SPD) – break-roller or ball.

In addition, investigated the combined surface hardening methods:

1. Electrophysical methods and superficial plastic deformation:

- SPD+ESA carbide electrode+SPD.

- Multiple coating ESA+SPD+ESA+SPD (4 passes) [1].

2. The combination of different types of electric-spark alloying:

- ESA graphite electrode following ESA carbide electrode, graphite electrode ESA and ESA copper electrode;

- Coating several layers ESA through different modes.

To assess the effectiveness of the laboratory used to strengthen research on friction machine on a "shaft-liner" [2]. Studies have shown an increase in wear resistance of annealed steel U7 (HV 220...240) with a combined surface after driving 25 km - 4 times, with mileage of 50 kilometers – 2,5 times, and hardened steel 45 (HV 337 and HV 420) with a combined coverage after driving 22 km by 5 times [2].

On the basis of the studies concluded that strengthening the combined surface coating scheme SPD→ESA→SPD→ESA→SPD [1] to create a multi-layer structure to increase the hardness of working surfaces 2-2,5 times and surface wear resistance in 1,5-5 times. When applying the combined wear-resistant coating scheme SPD→ESA→SPD→ESA→SPD [1] arising from hardened areas of hardened multilayer structure and several times re-hardened volumes, which increased the composition of tungsten carbide and lenses.

As a result, developed the technology increasing durability of machines such as shafts, crests locomotive bogies, axles cement packing machinery, which includes the pre-deformuvan plastic surface of the ball with a device that is installed in the tool carriers screw-cutting lathe, mechanized ESA solid smoke using a special alloy head, also located in the tool carriers. The running mode should be optimal. This primarily refers to efforts of breaking-in (pressure balloons for detail), supply and number of passes. Definition modes of breaking-in complicated by the fact that the relationship between him and the degree of roughness enhancement and nonlinear. Some optimization efforts by 10 mm balls held in [2]. It was established that the best steel for plastic load is 200...350 kg. Increased pressure on the surface leads to a violation of the integrity of the metal on the surface and the occurrence of peeling surface. The hardness of parts after breaking-in not exceed 50 HRC.

By emerging technologies hardened surface layer, which on the surface hardness up to 1200 HV. It is accompanied by grinding in polishing effect.

For the mechanical handling of parts such as bodies of revolution developed combined technology of wear-resistant coatings. In general terms, this technology involves the following steps [1]:

♦ preparation details, including machining to final size or the size of the allowance during grinding;

♦ preparation ESA installation work, including selection of the optimum currents to electrodes and materials;

♦ preparation for installation of SPD, including the selection of the best efforts;

♦ coating layer is made: SPD→ESA→SPD→ ESA→SPD;

♦ control measurements to determine the details of the thickness of the coating;

♦ final grinding to obtain details of the size required for drawing.

The technology by using specially designed equipment (Fig. 1). Fig. 1 shows a three-dimensional model diagram of complex devices combined to form durable coatings on parts such as the shaft.

Fig. 1. Three-dimensional model diagram of the installation combined to form a wear-resistant coating on the details of the type of shaft: 1 – a device for ESA; 2 – breaking-in device; 3 – caliper screw-cutting lathe; 4 – workpiece; 5 – electrically contact center

Conclusions:

The results of practical interest for various branches of engineering.

The technological developments providing formation of coatings with the required performance properties for different parts of machines.

Putting electric-spark coatings and composite coatings increases the operational stability of the machine parts 3-6 times.

References:

1. Патент на корисну модель №40858 Україна, МПК В23Н 1/00. Спосіб електроіскрового зміцнення поверхні металів та сплавів/ Маковей В.О., Бородій Ю.П., Куріхін В.С. (Україна) НТУУ. – № u2008 13977 Заявл. 04.12.2008; Опубл. 27.04.2009, Бюл. №8.

2. Бородий Ю.П. Экспериментальное исследование особенностей формирования поверхностного износостойкого слоя рабочих элементов разделительных штампов/ Бородий Ю.П., Маковей В.А.// Збірник наукових праць (галузеве машинобудування, будівництво). – Вип. 2 (37). – 2013. – ПолтНТУ. – С. 61-65.