High-temperature gas control valve

A high-temperature gas control valve for controlling a flow of a high-temperature gas, including:

• a cylinder section including a piston slidably disposed therein;
• a valve section including a valve seat made of metal and a valve element disposed facing the valve seat and movably in a direction to come into contact or separate from the valve seat in association with the sliding of the piston in the cylinder section;
• a diaphragm made of metal disposed between the valve seat and the valve element, the diaphragm being brought into contact with or separated from the valve seat by operation of an actuator, thereby opening and closing the valve;
• wherein a contact surface of at least one of the diaphragm and the valve seat is coated with an amorphous-carbon film so that when the valve is dried by moisture evaporation during use at a high temperature and the metal diaphragm comes into contact with the metal valve seat, the amorphous-carbon film having a small friction coefficient and high hardness prevents the generation of scratches in the diaphragm and the valve seat which are rubbing against each other in a dried state.