Features of the surface relief of steel and copper samples after HPT processing

Abstract

In this article, the surface of metallic material samples after HPT is investigated and analyzed. The initial blanks were copper and steel 10 (Fe-0.1% C) disks with a diameter of 10 mm and a height of 1 mm. The lower anvil had a groove with a diameter of 10 mm and a depth of 0.5 mm. The upper anvil was “flat” in all cases. HPT deformation was carried out at room temperature with applied design pressure of P = 6 GPa. Cu disks were subjected to HPT with the number of revolutions n = 2.5. Steel 10 (Fe-0.1% C) disks were subjected to HPT with the number of revolutions n = 5. On the basis of our previously obtained data, it was assumed that at HPT of Cu with n = 2.5 revolutions, slippage would be present, but it would not be total, and at HPT of steel with n = 5 revolutions, slippage would be total. The studies have shown that on the lower surface of the copper disk after HPT with n = 2.5 revolutions, a pattern of densely spaced concentric circles-scratches is observed, formed as a result of the incompatible movement of the anvils and the disk surface (sliding of the anvils along the surface) and caused by the presence of irregularities – the relief of the anvils. On the upper surface of the copper disk after HPT a similar pattern of concentric circles-scratches is much less pronounced, which is due to the joint movement of the anvils and the surface of the sample as a result of their “grabbing” (which causes deformation by torsion). Unlike the Cu sample, both on the upper and lower surfaces of the steel 10 disk after HPT with n = 5 revolutions densely spaced concentric circles-scratches of approximately the same intensity are observed. The scratches presumably formed in the similar way as a result of the incompatible movement of the anvils along both the upper and lower surfaces of the disk (sliding of the anvils along the surface). It is possible that sliding occurs first on one surface, then on the other one, since in the total sliding mode, sliding between the upper and lower surfaces may occur randomly.