A self-lubricating rolling bearing is provided. The chemical compositions in the inner rings and the outer rings of bearing are 3.4-3.7% C, 2.7-2.9% Si, 0.3-0.5% Mn, 0.3-0.5% Cr, ?0.05% S, ?0.05% P, 0.03-0.045% Residual Mg, and the remainder Fe. The total percent of the chemical compositions is 100%. The material for the inner and outer rings of the rolling bearing introduced in the invention is austempered ductile iron (ADI). In the microstructure of ADI, the diameter of the graphite nodules is less than 0.02 mm, the number of graphite spheres per square millimeter is more than 400, and the microstructure of the metal matrix in the ADI can be showed clearly only when it is observed on the microscope with a magnification more than 500. Eventually, the self-lubricating rolling bearings are made from the ADI.

The invention relates to a sliding element, in particular a piston ring, to a method for producing same, and to the use of the sliding element in a tribological system. The sliding element has a coating which has at least one adhesive layer and a MAX phase layer from the inside towards the outside. The MAX phase layer has the composition M.sub.n+1AX.sub.n (n=1, 2, 3), wherein M represents an element from the group Sc, Ti, V, Cr, Zr, Nb, Mo, Hf, and Ta, A represents an element from the group Al, Si, P, S, Ga, Ge, As, Cd, In, Sn, Tl, and Pb, and X represents the elements C or N.

Provided is a cast iron material from which excellent friction characteristics can be obtained. Provided is the cast iron material containing C and Fe as a composition, and further containing Cr as the composition in 1.0 to 3.5% in terms of mass %. The cast iron material is used in a sliding component sliding under an environment of lubricating oil to which an additive containing Mo as a constituent element, such as MoDTC, is added. Cr contained in the cast iron material promotes a decomposition reaction of the additive containing Mo added to the lubricating oil to form a film of molybdenum disulfide, the film having low friction. Thus, the fiction can be reduced.

Provided is a cast iron material from which excellent friction characteristics can be obtained. Provided is the cast iron material containing C and Fe as a composition, and further containing Cr as the composition in 1.0 to 3.5% in terms of mass %. The cast iron material is used in a sliding component sliding under an environment of lubricating oil to which an additive containing Mo as a constituent element, such as MoDTC, is added. Cr contained in the cast iron material promotes a decomposition reaction of the additive containing Mo added to the lubricating oil to form a film of molybdenum disulfide, the film having low friction. Thus, the fiction can be reduced.

A spheroidal graphite cast iron alloy comprises, in % by weight, in addition to addition elements, the following elements: Ni between 3.5% and 7%, Cu between 0.5% and 3%, Mo between 0.15% and 1%, the remainder being iron and inevitable impurities. The spheroidal graphite cast iron alloy may be used in manufacturing a part such as cogwheels and gear rims. The method of manufacturing the part may comprise casting a rough casting blank, notably into a mold, and letting the rough casting blank cool in the mold, thus obtaining the part.

A spheroidal graphite cast iron alloy comprises, in % by weight, in addition to addition elements, the following elements: Ni between 3.5% and 7%, Cu between 0.5% and 3%, Mo between 0.15% and 1%, the remainder being iron and inevitable impurities. The spheroidal graphite cast iron alloy may be used in manufacturing a part such as cogwheels and gear rims. The method of manufacturing the part may comprise casting a rough casting blank, notably into a mold, and letting the rough casting blank cool in the mold, thus obtaining the part.

A spheroidal graphite cast iron meeting N.sub.(5-)250, N.sub.(5-20)/N.sub.(5-)0.6, and N.sub.(30-)/N.sub.(5-)0.2, wherein N.sub.(5-) represents the number (/mm.sup.2) of graphite particles having equivalent-circle diameters of 5 m or more, N.sub.(5-20) represents the number (/mm.sup.2) of graphite particles having equivalent-circle diameters of 5 m or more and less than 20 m, and N.sub.(30-) represents the number (/mm.sup.2) of graphite particles having equivalent-circle diameters of 30 m or more, among graphite particles observed in an arbitrary cross section of at least 1 mm.sup.2.

A spheroidal graphite cast iron meeting N.sub.(5-)250, N.sub.(5-20)/N.sub.(5-)0.6, and N.sub.(30-)/N.sub.(5-)0.2, wherein N.sub.(5-) represents the number (/mm.sup.2) of graphite particles having equivalent-circle diameters of 5 m or more, N.sub.(5-20) represents the number (/mm.sup.2) of graphite particles having equivalent-circle diameters of 5 m or more and less than 20 m, and N.sub.(30-) represents the number (/mm.sup.2) of graphite particles having equivalent-circle diameters of 30 m or more, among graphite particles observed in an arbitrary cross section of at least 1 mm.sup.2.

There is provided with spheroidal graphite cast iron having excellent gas defect resistance where gas defects such as pinholes attributable to the free N are small in number and having mechanical characteristics and machinability equal to or greater than the conventional ones. The spheroidal graphite cast iron consists of, in mass ratio, C: 3.3 to 4%; Si: 2 to 3%; P: not more than 0.05%; S: not more than 0.02%; Mn: not more than 0.8%; Cu: not more than 0.8% (0 is not included); Mg: 0.02 to 0.06%; Ti: 0.01 to 0.04%; V: 0.001 to 0.01%; Nb: 0.001 to 0.01%; and N: 0.004 to 0.008%, with the remnant substantially consisting of Fe and an inevitable impurity.

There is provided with spheroidal graphite cast iron having excellent gas defect resistance where gas defects such as pinholes attributable to the free N are small in number and having mechanical characteristics and machinability equal to or greater than the conventional ones. The spheroidal graphite cast iron consists of, in mass ratio, C: 3.3 to 4%; Si: 2 to 3%; P: not more than 0.05%; S: not more than 0.02%; Mn: not more than 0.8%; Cu: not more than 0.8% (0 is not included); Mg: 0.02 to 0.06%; Ti: 0.01 to 0.04%; V: 0.001 to 0.01%; Nb: 0.001 to 0.01%; and N: 0.004 to 0.008%, with the remnant substantially consisting of Fe and an inevitable impurity.