Graded composition and structure in nanocrystalline Ni–Co alloys for decreasing internal stress and improving tribological properties

In this paper, nanocrystalline Ni?Co alloys with continuously graded composition and structure were produced by the electrodeposition method. The internal stress of the graded Ni?Co nanocrystalline alloys generated during the electrocrystallization and the tribological properties were investigated and compared with Ni?Co alloys with a uniform structure. The results show that with continuous changes in composition and structure, the internal stress generated during the electrodeposition process was decreased to approximately the minimum level. Additionally, the graded Ni?Co nanocrystalline alloys exhibited a remarkably improved wear resistance and a much lower friction coefficient compared with the Ni?Co alloys with a uniform structure under the dry sliding wear conditions. And the graded Ni?Co nanocrystalline alloys retain perfect friction and wear properties as the annealing temperature increases up to 400?C.