Tribological and mechanical investigation of multi-directional forged nickel.

Tailoring material properties to specific application requirements is one of the major challenges in materials engineering. Grain size is a key factor affecting physical and mechanical properties of polycrystals materials, the presented work enables insight into how the pure nickel properties are affected by application of multi-directional forging (MDF) as a well-known severe plastic deformation method. It is demonstrated that the hardness and wear rate are improved by imposing MDF process. The rate of enhancement is reduced at the higher pass numbers. It is also shown that the application of MDF process changed the mechanism of wear. Non-MDF sample's surface shows spalling and delamination, while the dominated wear mechanism of final pass sample is peeling with a slight of adhesion. The change of wear mechanism can be associated with the reduction of friction coefficient of the deformed sample. By considering the linear correlation between the hardness and wear rate, a simple and fast procedure is proposed to estimate the wear rate of sample after the different MDF pass numbers using the corresponding hardness magnitude. Additionally, the attained microstructure of the final pass sample shows a combination of ultrafine grains and micro shear bands.