A seal or bearing comprising a combination of a movable member and a stationary member, either one of the movable and stationary members being made of a low thermal expansion coefficient material, and the other being made of a carbon containing material, wherein a sliding surface of the movable or stationary member which is made of the low thermal expansion coefficient material is irradiated with an ion beam consisting essentially of nitrogen ions at the same time as titanium is vacuum-deposited on the sliding surface, thereby forming a thin titanium nitride film on the sliding surface, which provide a seal or bearing which has a reduced coefficient of friction, and which is improved in wear resistance.