In precision sealing applications, the performance of a seal does not depend only on the surface roughness (Ra, Rz, Rt) of the mating parts — surface hardness and treatment are equally critical. An optimal combination of surface finish, hardness, and coating ensures consistent contact pressure, minimizes wear, and extends service life. Improper surface conditions, on the other hand, often lead to leakage, abrasion, or premature seal failure. Importance of Surface Hardness Surface hardness...