Effect of Interface Friction on Surface Integrity and Microstructure during Extrusion of Pure Nickel

The friction behavior of the billet–die interface during the pure nickel N6 extrusion process has an important decisive effect on the surface wear, microstructure control of the workpiece. Herein, field extrusion and finite element simulation are used. The influence of different interface states on the wear behavior, microstructure, and texture of pure nickel surface is realized by changing the lubrication effect between the billet and the die. The results show that the interface state has a great influence on the interface temperature and stress, which leads to different wear behaviors, microstructures, and textures of the workpiece surface. The use of lubricant reduces the shearing force of the billet–die interface, resulting in lower heat generation at the interface, and reduced uneven deformation of the billet. As a result, the surface quality of the workpiece is relatively good, but uneven lubrication is the main cause of tearing damage on the surface of the billet. The grain morphology and grain boundary distribution on the surface of the lubricating extruded bar are uniform, the microtexture strength is weak, and the Schmidt factor is large. In contrast, the opposite is true in the absence of lubrication. The interface state between billet and die has a great influence on the wear behavior and microstructure of pure nickel during extrusion. Compared with the lubricated extrusion, the spalling wear and fatigue wear occur on the surface without lubrication. The surface temperature, stress, and microstructure of the workpiece show gradient changes under the condition of unlubricated extrusion. In contrast, the lubrication conditions are uniform.