Inlet-type expansion valveThe valve seat includes a circular valve seat body, with the sealing surface of the valve seat positioned on a plane near the valve body. Thermal spraying utilizes the contact between the outer surface of the sealing boss of the valve seat and the sealing surface of the valve body to provide a new type of metal seal between the valve seat and body. Under the same working conditions, due to the reduced contact area, the sealing pressure ratio increases, preventing leakage.