Increasing the life of restored machine parts by residual stress management

Restoration of machine parts ensures the repeated use of up to 70 % of worn parts. Restoration of machine parts is economically efficient; the cost of restoration usually does not exceed 30 % of the cost of new parts. However, the application of most restoration methods and technologies leads to a decrease in their life in comparison with new ones. For high-loaded shafts the fatigue resistance is the main factor determining their life. The state of the surface layer is the main factor affecting the fatigue strength of the parts. The dominant role in increasing the fatigue resistance of the machine restored parts belongs to the physical and mechanical properties of the surface layer, hardening and residual stresses. The article considers the restoration technology using electro-contact welding of a metal strip. Data on the surface residual stresses resulting from the welding of the coating are obtained. The results of measurements showed a high loading of the surface layer. The ways of residual stresses reduction in the restored parts using surface plastic deformation and electro-contact hardening are considered. The use of electro-contact hardening is recommended to improve the fatigue life of restored parts using electro-contact welding of metal tape. The application of this process allows increasing the endurance limit of the restored parts in 1.5...2.5 times.