To provide a composition for a heat cycle system having favorable lubricating properties and comprising a working fluid for heat cycle which has a low global warming potential and which can replace R410A and a heat cycle system employing the composition. A composition for a heat cycle system comprising a working fluid for heat cycle containing trifluoroethylene, and a refrigerant oil (for example, an ester refrigerant oil, an ether refrigerant oil, a polyglycol refrigerant oil or a hydrocarbon refrigerant oil), and a heat cycle system employing the composition for a heat cycle system.

To provide a composition for a heat cycle system having favorable lubricating properties and comprising a working fluid for heat cycle which has a low global warming potential and which can replace R410A and a heat cycle system employing the composition. A composition for a heat cycle system comprising a working fluid for heat cycle containing trifluoroethylene, and a refrigerant oil (for example, an ester refrigerant oil, an ether refrigerant oil, a polyglycol refrigerant oil or a hydrocarbon refrigerant oil), and a heat cycle system employing the composition for a heat cycle system.

A method including substituting an atmosphere in a space, in which a sliding surface formed of a metal or a ceramic material, and a slid surface are disposed, with a gas atmosphere containing a hydroxyl group-containing compound and at least one of hydrogen and nitrogen, and relatively sliding the sliding surface against the slid surface by a Hertzian contact stress of 1.0 GPa or more in the space under the gas atmosphere containing the hydroxyl group-containing compound at least one of hydrogen and nitrogen. As a result, it is possible to form, on the sliding surface, a low-friction coating that stably exhibits a significantly low friction coefficient, for example, of 10.sup.4 order (less than 0.001).

A method including substituting an atmosphere in a space, in which a sliding surface formed of a metal or a ceramic material, and a slid surface are disposed, with a gas atmosphere containing a hydroxyl group-containing compound and at least one of hydrogen and nitrogen, and relatively sliding the sliding surface against the slid surface by a Hertzian contact stress of 1.0 GPa or more in the space under the gas atmosphere containing the hydroxyl group-containing compound at least one of hydrogen and nitrogen. As a result, it is possible to form, on the sliding surface, a low-friction coating that stably exhibits a significantly low friction coefficient, for example, of 10.sup.4 order (less than 0.001).

Inside a sealed container (101) of a refrigerant compressor (100), lubricating oil (103) having a kinematic viscosity at 40 C. of 0.1 mm.sup.2/S to 5.1 mm.sup.2/S is stored, and an electric element (106) and a compression element (107) are accommodated. The compression element (107) is provided with, as a shaft part, a crankshaft (108) comprising a main shaft (109) and an eccentric shaft (110), and as bearing parts, a main bearing (114) that axially supports the main shaft (109) and an eccentric bearing (119) that axially supports the eccentric shaft (110). At least one surface of the main shaft (109) and the eccentric shaft (110) is subjected to a surface treatment, e.g., formation of an oxide film, having a hardness equal to or greater than that of a bearing part (the main bearing (114) or the eccentric bearing (119)). Satisfactory reliability in sliding parts can thereby be achieved even if lubricating oil having lower viscosity is used.

Inside a sealed container (101) of a refrigerant compressor (100), lubricating oil (103) having a kinematic viscosity at 40 C. of 0.1 mm.sup.2/S to 5.1 mm.sup.2/S is stored, and an electric element (106) and a compression element (107) are accommodated. The compression element (107) is provided with, as a shaft part, a crankshaft (108) comprising a main shaft (109) and an eccentric shaft (110), and as bearing parts, a main bearing (114) that axially supports the main shaft (109) and an eccentric bearing (119) that axially supports the eccentric shaft (110). At least one surface of the main shaft (109) and the eccentric shaft (110) is subjected to a surface treatment, e.g., formation of an oxide film, having a hardness equal to or greater than that of a bearing part (the main bearing (114) or the eccentric bearing (119)). Satisfactory reliability in sliding parts can thereby be achieved even if lubricating oil having lower viscosity is used.

raction fluid additive combination that is usable with any traction fluids base stock is provided. To optimize the traction, low temperature viscosity and shear stability performance, a combination of a polyisobutene and a polymethacrylate may be added to a base oil to obtain a traction fluid with good low temperature viscosity without degrading the shear strength properties of the fluid. To minimize foaming of the traction fluid, a combination of one, two, or more anti-foaming agents may be added to the fluid in addition to a standard additive package.

raction fluid additive combination that is usable with any traction fluids base stock is provided. To optimize the traction, low temperature viscosity and shear stability performance, a combination of a polyisobutene and a polymethacrylate may be added to a base oil to obtain a traction fluid with good low temperature viscosity without degrading the shear strength properties of the fluid. To minimize foaming of the traction fluid, a combination of one, two, or more anti-foaming agents may be added to the fluid in addition to a standard additive package.

To provide a composition for a heat cycle system having favorable lubricating properties and comprising a working fluid for heat cycle which has a low global warming potential and which can replace R410A and a heat cycle system employing the composition. A composition for a heat cycle system comprising a working fluid for heat cycle containing trifluoroethylene, and a refrigerant oil (for example, an ester refrigerant oil, an ether refrigerant oil, a polyglycol refrigerant oil or a hydrocarbon refrigerant oil), and a heat cycle system employing the composition for a heat cycle system.

To provide a composition for a heat cycle system having favorable lubricating properties and comprising a working fluid for heat cycle which has a low global warming potential and which can replace R410A and a heat cycle system employing the composition. A composition for a heat cycle system comprising a working fluid for heat cycle containing trifluoroethylene, and a refrigerant oil (for example, an ester refrigerant oil, an ether refrigerant oil, a polyglycol refrigerant oil or a hydrocarbon refrigerant oil), and a heat cycle system employing the composition for a heat cycle system.