Scuffing experiments were conducted using diameter disks both with and without a metal-containing, carbon-based hard coating. The operating conditions in the experiments were severe with sliding speeds up to and maximum Hertzian contact pressures up to . The disks were of alloy steel, which was case carburized and hardened followed by axial grinding. Four different surface conditions were investigated as follows: ground/uncoated, ground/coated, superfinished/uncoated, and superfinished/coated. Experiments were also carried out in which ground/coated disks were run against ground/uncoated disks. The results of the experiments show that the addition of the hard coating to the ground disks significantly improved both their scuffing resistance and frictional behavior, but the coating was less effective in producing an improvement in the durability and friction of the superfinished disks.