Iron-based sintered alloy, iron-based sintered-alloy member and production process for them

A production process for an iron-based sintered alloy, the production process comprising:

• making a powder compact by press forming a raw material powder, in which an Fe-system powder which contains Cr and Mo and in which the major balance is composed of Fe, and a C-system powder in which C is the major component, are mixed with an Fe—Mn—Si strengthening powder consisting of Fe, Mn and Si wherein a compositional ratio (Mn:Si) of the Mn to the Si is 1:3-1:1;
• wherein, when the entirety of the iron-based sintered alloy is taken as 100% by mass,
• Cr is 0.2-5.0% by mass;
• Mo is 0.1-1% by mass;
• Mn is 0.1-1.2% by mass;
• Si is 0.1-1.2% by mass;
• C is 0.1-0.7% by mass;
• and
• the major balance is composed of Fe;
• and
• sintering the powder compact in an oxidation preventive atmosphere.

A production process for an iron-based sintered alloy member, the production process comprising:

• press forming a raw material powder, in which an Fe-system powder composed of at least one of pure iron and iron alloy, and a C-system powder composed of C mainly, are mixed with an Si-system powder composed of simple substance, alloy or compound of Si, thereby obtaining a powder compact having a green density ratio (ρ/ρ0′×100%), the ratio of a green density (ρ) to a sintered-body theoretical density (ρ0′), of 96% or more;
• wherein, when the entirety of the iron-based sintered alloy is taken as 100% by mass, silicon (Si) is 0.01-2% by mass;
• carbon (C) is 0.1-0.8% by mass;
• and Fe is the major balance;
• and
• sintering the powder compact in an oxidation preventive atmosphere, wherein the iron-based sintered alloy has a sintered density ratio of 96% or more.