A valve component for a faucet includes a substrate, a first layer of material provided above the substrate in an amount sufficient to improve abrasion resistance of the substrate, and a second layer of material provided above the first layer of material. The second layer of material includes amorphous diamond having sp.sup.3 bonding of at least about 40%, a hardness of at least about 45 GPa, and an elastic modulus of at least about 400 GPa.