Abstract: The present invention provides a valve seat of a Co-free, sintered iron-based alloy having excellent heat resistance, oxidation resistance and wear resistance, as well as excellent machinability, which is usable for internal combustion engines using a gas fuel. The valve seat is produced by using a prealloy containing 12% or more by mass of Cr in a matrix for, and hard particles having high strength and hardness at high temperatures are used, such that the entire valve seat has a composition comprising by mass 5.0-20.0% of Cr, 0.4-2.0% of Si, 2.0-6.0% of Ni, 5.0-25.0% of Mo, 0.1-5.0% of W, 0.5-5.0% of V, 1.0% or less of Nb, and 0.5-1.5% of C, the balance being Fe and inevitable impurities.

Abstract: The present invention provides a valve seat of a Co-free, sintered iron-based alloy having excellent heat resistance, oxidation resistance and wear resistance, as well as excellent machinability, which is usable for internal combustion engines using a gas fuel. The valve seat is produced by using a prealloy containing 12% or more by mass of Cr in a matrix for, and hard particles having high strength and hardness at high temperatures are used, such that the entire valve seat has a composition comprising by mass 5.0-20.0% of Cr, 0.4-2.0% of Si, 2.0-6.0% of Ni, 5.0-25.0% of Mo, 0.1-5.0% of W, 0.5-5.0% of V, 1.0% or less of Nb, and 0.5-1.5% of C, the balance being Fe and inevitable impurities.

Abstract: An iron-based sintered alloy valve seat having excellent wear resistance and machinability, which can be used for high-power diesel engines, an intermetallic compound having Vickers hardness Hv of 800-1200 is used, and C and P in the composition of the iron-based sintered valve seat are by mass 1.2-1.6% and 0.80-1.35%, respectively.

Abstract: To provide an iron-based sintered alloy valve seat having excellent wear resistance and machinability, which can be used for high-power diesel engines, an intermetallic compound having Vickers hardness Hv of 800-1200 is used, and C and P in the composition of the iron-based sintered valve seat are by mass 1.2-1.6% and 0.80-1.35%, respectively.

Abstract: In a valve seat made of an iron-based, composite sintered alloy having hard particles and a solid lubricant dispersed therein to have high wear resistance and good machinability, which is usable in high-power fuel direct injection engines with improved fuel efficiency and low emission, relatively coarse solid lubricant particles in such an amount as not to drastically reduce the strength of a sintered body are dispersed to provide self-lubrication, and as fine solid lubricant particles as not hindering the bonding of matrix particles are dispersed to improve machinability.

Abstract: A valve seat of an iron-based sintered alloy having high wear resistance in a wide temperature range, which can be used in direct injection engines with improved fuel efficiency, low emission and high power, is obtained by limiting the amount of a solid lubricant dispersed in the matrix of the valve seat of an iron-based sintered alloy, and dispersing at least two types of hard particles having different hardnesses in the matrix, thereby providing high strength and self-lubrication, as well as improved wear resistance under no lubrication in a wide temperature range.

Abstract: In a valve seat made of an iron-based, composite sintered alloy having hard particles and a solid lubricant dispersed therein to have high wear resistance and good machinability, which is usable in high-power fuel direct injection engines with improved fuel efficiency and low emission, relatively coarse solid lubricant particles in such an amount as not to drastically reduce the strength of a sintered body are dispersed to provide self-lubrication, and as fine solid lubricant particles as not hindering the bonding of matrix particles are dispersed to improve machinability.

Abstract: An iron-based sintered alloy having improved thermal and mechanical strength is provided. The iron-based sintered alloy with dispersed hard particles comprises: a matrix comprising, by weight, 0.4 to 2% silicon (Si), 2 to 12% nickel (Ni), 3 to 12% molybdenum (Mo), 0.5 to 5% chromium (Cr), 0.6 to 4% vanadium (V), 0.1 to 3% niobium (Nb), 0.5 to 2% carbon (C), and the reminder of iron (Fe); and hard particles comprising 60 to 70% molybdenum (Mo), 0.3 to 1% boron (B), 0.1% or less carbon (C), and the reminder of iron (Fe). The hard particles are dispersed in the matrix in an amount in the range of 3 to 20% based on the entire alloy. They are sintered to produce the iron-based sintered alloy. Addition of boron into the ferromolybdenum hard particles enhances the wettability of the ferromolybdenum hard particles to prevent the hard particles from falling off the matrix.

Abstract: An iron-based sintered alloy having improved thermal and mechanical strength is provided. The iron-based sintered alloy with dispersed hard particles comprises: a matrix comprising, by weight, 0.4 to 2% silicon (Si), 2 to 12% nickel (Ni), 3 to 12% molybdenum (Mo), 0.5 to 5% chromium (Cr), 0.6 to 4% vanadium (V), 0.1 to 3% niobium (Nb), 0.5 to 2% carbon (C), and the reminder of iron (Fe); and hard particles comprising 60 to 70% molybdenum (Mo), 0.3 to 1% boron (B), 0.1% or less carbon (C), and the reminder of iron (Fe). The hard particles are dispersed in the matrix in an amount in the range of 3 to 20% based on the entire alloy. They are sintered to produce the iron-based sintered alloy. Addition of boron into the ferromolybdenum hard particles enhances the wettability of the ferromolybdenum hard particles to prevent the hard particles from falling off the matrix.

Abstract: An iron-based sintered alloy, which consists of from 0.5 to 5% of Ni, from 0.5 to 4% of Cr, from 0.5 to 2% of C, the balance being Fe and unavoidable impurities, and which has a micro-structure comprising an iron-based matrix containing Ni and a part of Cr as solutes and carbides containing the other part of Cr and dispersed in the matrix. The iron-based sintered alloy is appropriate for use as a valve seat of an internal combustion engine. Wear resistance is maintained at a moderate level while the additive amount of alloying elements is decreased to attain low cost.

Abstract: An iron-based sintered alloy, which consists of from 0.5 to 5% of Ni, from 0.5 to 4% of Cr, from 0.5 to 2% of C, the balance being Fe and unavoidable impurities, and which has a micro-structure comprising an iron-based matrix containing Ni and a part of Cr as solutes and carbides containing the other part of Cr and dispersed in the matrix. The iron-based sintered alloy is appropriate for use as a valve seat of an internal combustion engine. Wear resistance is maintained at a moderate level while the additive amount of alloying elements is decreased to attain low cost.