Piston ring with MoN/Cr/CrN/Cr nano composite ultra-thick coating and preparation method of piston ring

The invention discloses a piston ring with an MoN/Cr/CrN/Cr nano composite ultra-thick coating. The piston ring comprises a piston ring base body, and an MoN/Cr/CrN/Cr nano composite ultra-thick coating which is adhered to the surface of the piston ring base body, wherein the MoN/Cr/CrN/Cr nano composite ultra-thick coating comprises a metallurgy layer, a metal layer, a stress gradient layer and a working layer; and the preparation method comprises the following steps: carrying out argon plasma etching on the pre-treated piston ring base body; bombarding the surface of the piston ring base body by using Cr ions, so as to obtain the metallurgy layer; sequentially depositing the Cr metal layer and the stress gradient layer; and finally assisting a multi-arc ion plating method in depositing an MoN/Cr/CrN/Cr/MoN coating or an MoN/Cr/CrN/Cr periodic coating by adopting an ion source, wherein the surface of the MoN/Cr/CrN/Cr periodic coating is an MoN layer. The piston ring has the advantages that the piston ring has high heat stability of the CrN coating and the self-lubricating property of the MoN coating; and the preparation procedure is simple and easy to control.