The National Transport University Bulletin

Abstract

The article considers the direction of energy saving which can be solved during the introduction of surface hardening technologies. Purpose: to create a method of forming wear-resistant coatings by electric arc spraying (EDN) and to establish the impact of its technological modes on the properties of coatings, to improve performance (wear resistance) and service life of motor shafts. Object of research – the process of coating parts such as «shaft» by EDN. The study consisted of the following stages: analysis of the operating conditions of parts such as «shaft» of engines, the establishment of their main defects and ways to eliminate them, choice of recovery method and its characteristics; study of the properties of the restored surfaces of shafts with coatings: porosity, adhesive and cohesive strength of the coating system-detail, durability, microhardness and wear resistance; optimization of the EDN mode of coatings and development of the technological process of shaft restoration and practical recommendations. Mathematical models have been developed that describe the relationship of technological parameters of the coating process with their properties and the optimal process parameters that provide the necessary properties of coatings have been determined. It was found that the adhesion strength of the coatings was 100...150 MPa, and the porosity 5...10 %. It was decided to investigate the mechanical properties of the system «restored surface-coating» (cohesive and adhesive strength, deformability, stress level in the coating and the zone of adhesive contact, the type of destruction of the system) on one sample per test using experimental methods. It is proposed to determine the optimal ratio of adhesive and cohesive strength – using the criterion of adhesive-cohesive strength, which will control the quality of the coating and its connection with the renewable surface, consisting in obtaining the desired structure in the area of their connection by controlling the deformation etc. On the basis of theoretical and experimental researches the technology of restoration of shafts which consists in EDN of a wire 40Х13 is developed. Developed TP shaft restoration, which consists of the following operations: washing, defecting, machining (MO) to remove the defective layer, jet-abrasive treatment (CAO) before EDN to increase the roughness of the recoverable surface and the strength of the coating, EDN coatings, clean and control of necks of a shaft with a sprayed covering. Laboratory and bench tests of shafts showed that the wear resistance of surfaces restored using EDN technology is 2.5-5 times higher than surfaces restored by gas-flame spraying (GPN) and 1.5-1.7 times – compared to new shafts. The service life of restored shafts has increased by 2...2.5 times compared to new parts and parts restored by GPN.

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