Abstract: Provided is a valve seat having excellent strength and wear resistance. In a valve seat using an iron-based sintered alloy, an oxide mains composed of triiron tetroxide is formed by oxidation treatment on the surface and interior of the iron-based sintered alloy, and the average area ratio of the oxide mainly composed of triiron tetroxide in a cross section of the iron-based, sintered alloy in the state prior to installation on a cylinder head is 5 to 20%. Preferably, the iron-based sintered alloy contains hard particles formed from at least one compound of carbides, silicides, nitrides, borides, and intermetallic compounds containing one or more elements selected from groups 4a to 6a of the periodic table, and the average area ratio of the hard particles in the cross section of the iron-based sintered alloy in the state prior to installation on a cylinder head is 5 to 45%.

Abstract: Provided is a valve seat having excellent strength and wear resistance. In a valve seat using an iron-based sintered alloy, an oxide mains composed of triiron tetroxide is formed by oxidation treatment on the surface and interior of the iron-based sintered alloy, and the average area ratio of the oxide mainly composed of triiron tetroxide in a cross section of the iron-based, sintered alloy in the state prior to installation on a cylinder head is 5 to 20%. Preferably, the iron-based sintered alloy contains hard particles formed from at least one compound of carbides, silicides, nitrides, borides, and intermetallic compounds containing one or more elements selected from groups 4a to 6a of the periodic table, and the average area ratio of the hard particles in the cross section of the iron-based sintered alloy in the state prior to installation on a cylinder head is 5 to 45%.