A coated article includes a substrate, and a coating disposed on a surface of the substrate. The coating comprises a transition metal dichalcogenide (TMD). A method of forming a coating includes dispersing a transition metal dichalcogenide (TMD) and optionally tungsten carbide in a solvent to form a mixture, spraying the mixture on a surface of a substrate, evaporating the solvent, and forming a coating on the substrate comprising the TMD.

Molybdenum disulfide particles include a 2H crystal structure and a 3R crystal structure of molybdenum disulfide, in which a presence ratio of the 3R crystal structure in a crystal phase of molybdenum disulfide is 10% or more, and a crystallite size of the 3R crystal structure calculated by extended-type Rietveld analysis based on an analysis formula L=K/( cos ) using a profile obtained from powder X-ray diffraction (XRD) using Cu-K rays as an X-ray source is 1 nm or more and 150 nm or less (in the above formula, K is an instrumental constant that depends on an XRD optical system (an incident side and a detector side) and settings, L is a crystallite size [m], is a measured X-ray wavelength [m], is a half width [rad], and is a Bragg angle of a diffraction line [rad]).

Provided is a composition for a refrigeration machine capable of reducing a friction coefficient in friction between sliding members in a refrigeration machine, and a composition kit for a refrigeration machine for providing the composition for a refrigeration machine. A composition for a refrigeration machine of the present disclosure includes a refrigeration machine oil, nanodiamond particles dispersed in the refrigeration machine oil, and a dispersant. The refrigeration machine oil preferably contains a polyvinyl ether, a polyol ester, a polyalkylene glycol, an alkylbenzene, or a mineral oil. The composition kit for a refrigeration machine of the present disclosure includes a refrigeration machine oil (A) containing a base oil and nanodiamond particles dispersed in the base oil, and a refrigerant (B).