Powder-metallurgy valve seat insert and preparation method thereof

The invention discloses a powder-metallurgy valve seat insert. The invention is characterized in that the powder-metallurgy valve seat insert is prepared from the following raw materials in parts by weight: 64-65 parts of valve steel powder, 4.3-4.5 parts of Ni, 1.3-1.5 parts of Cu, 23-25 parts of tool steel powder, 0.3-0.5 part of graphite powder, 5.3-5.5 parts of Mo, 62.3-64.5 parts of iron powder, 1.4-1.8 parts of Ti, 2.1-2.4 parts of B, 0.5-0.85 part of Li and 2-3 parts of assistant. The high-temperature wear-resistant corrosion-resistant valve steel powder, high-temperature thermosetting iron alloy powder and graphite powder are added to enhance the wear resistance and lubricating property of the valve seat insert, so that the manufactured valve seat insert has the advantages of compact structure, favorable microstructure, fewer pores, high structural stiffness, high hardness, high fatigue resistance and high tensile strength.