Method for producing a valve seat made of an Fe-based sintered alloy that exhibits excellent wear resistance under high surface pressure application conditions

摘要

Production of iron-based sintered alloy valve seat involves using iron-based alloy powder for forming a matrix and cobalt-based alloy powder for forming a hard dispersion phase. Both alloy powders have an average particle size of 20-50 Micro. Solid phase sintering under vacuum is conducted to form a pressed compact made of the mixed powders. Production of iron-based sintered alloy valve seat involves using iron (Fe)-based alloy powder as a raw material powder for forming a matrix and a cobalt (Co)-based alloy powder as a raw material for forming hard dispersion phase. The Fe-based alloy powder comprises (weight %) carbon (C) (0.5-1.5), nickel (Ni) (0.1-3), molybdenum (Mo) (0.5-3), Co (3-8), chromium (Cr) (0.2-3), and Fe and impurities (balance). The Co-based alloy powder comprises (weight %) Mo (20-32), Cr (5-10), silicon (Si) (0.5-4), and Co and impurities (balance). Both the Fe-based and Co-based alloy powders have average particle size of 20-50 Micro. The process includes conducting solid phase sintering of a pressed compact formed from a mixed powder generated by mixing the Co-based alloy powder into the Fe-based alloy powder under vacuum conditions at 25-35 weight %. The Co, Cr, and Si of the Co-based alloy powder are diffused and migrate into the matrix. The Fe component of the Fe-based alloy powder to diffuse and migrate concurrently into the hard dispersion phase to improve adhesion of the hard dispersion phase to the matrix and to form an Fe-based sintered alloy substrate with a porosity of 10-20% measured by an X-ray microanalyzer. An Fe-Co alloy matrix comprises (weight %) C (0.5-1.5), Ni (0.1-3), Mo (0.5-3), Co (13-22), Cr (1-5), Si (0.1-1), and Fe and impurities (balanced) uniformly distributed a hard dispersion phase of a Mo-Fe-Co alloy having a composition comprising (weight %) Fe (20-30), Co (13-22), Cr (1-5), Si (0.3-3), and Mo and impurities (balanced). The matrix has a 2 phase mixed system of an Fe-Co alloy phase and a Mo-Co alloy phase. The Fe-based sintered alloy substrate is infiltrated with copper or a copper alloy. An independent claim is also included for a valve seat obtained from the above process.