Abstract: The present invention provides a sliding member, of which the surface cavities do not disappear even after progress of wear of the sliding surface, which permits maintenance of a satisfactory seizure resistance, and has better seizure resistance, wear resistance and strength properties than in a sliding member having a porous chrome plating layer formed thereon in the conventional art. The sliding member of the invention has a laminated hard Cr plating layer comprising a plurality of hard Cr plating layers laminated on the sliding surface. Micro-cracks are formed on each hard Cr plating layer surface, and the micro-cracks of each hard Cr plating layer form micro-pores independent in the film-forming direction. On the cross-section of the laminated hard Cr plating layer, the porosity should be within a range of from 0.5 to 4.5%.

Abstract: The present invention provides a synchronizer ring excellent in strength and abrasion resisting property, used in a speed change gear. This synchronizer ring according to the invention is consisted of, by weight, C:0.2˜1.0%, Ni:1.0˜6.0%, Mo:0.6˜3.0%, Cu:1.0˜4.0% and the reminder Fe and inevitable impurities, and is made of Fe sintered alloy of which base composition comprises of mainly martonsite and bainite. And the base composition is preferably consisted of, by volume, martensite: 57˜80%, bainite: 17˜40%, austenite: 8% or less.

Abstract: A synchronizer ring performing synchronous sliding operation with and separating operation from a rotating object member, is composed of an Fe sintered alloy. The Fe sintered alloy comprises carbon of from 1.2 wt. % to 2.0 wt. %, copper of from over 15.0 wt. % to 25.0 wt. %, and the balance being iron and incidental impurities. A free Cu phase is precipitated in a matrix of the synchronizer ring. The synchronizer ring has a high scuffing resistance, an excellent friction characteristic, and sufficient abrasion resisting property and strength, and moreover, provides an easy manufacture thereof by means of a size working and is stable in quality.

Abstract: A synchronizer ring having a stabilized friction characteristic relative to a taper cone and having sufficient mechanical strength and anti-abrasion characteristic. The synchronizer ring is made from a ferrous sintered alloy containing 0.2 to 1.0% by weight of carbon, 8.0 to 15.0% by weight of copper, 0.1 to 7.0% by weight of at least one component selected from a group consisting of chromium, manganese, molybdenum, and phosphorus, and balance iron and inevitable impurities. A free copper is precipitated in a matrix of the sintered alloy. Porosity of the sintered alloy is from 3 to 8 vol %.