**Xinfang Huang 1, Zhiwen Xie 1,\*, Kangsen Li 2, Qiang Chen 3, Yongjun Chen 1,4 and Feng Gong 2,\***


Received: 27 December 2019; Accepted: 21 February 2020; Published: 25 February 2020

**Abstract:** CrWN glass molding coatings were deposited by plasma enhanced magnetron sputtering (PEMS). The microstructure and thermal stability of these coatings were investigated by X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscope, transmission electron microscope, atomic force microscope and nanoindentation tests. The as-deposited coating exhibited an aggravated lattice expansion resulting in a constant hardness enhancement. The vacuum annealing induced surface coarsening and the spinodal decomposition of the coating accompanied by the formation of nm-sized c-CrN, c-W2N, and h-WN domains. The annealed coating with low W content had mainly a face-centered cubic (f.c.c) matrix, strain fields caused by lattice mismatch caused hardness enhancement. Following an increase in W content, the annealed coating showed a mixed face-centered cubic (f.c.c) and hexagonal close-packed (h.c.p) matrix. The large volume fraction of h-WN phases seriously weakened the coating strengthening effect and caused an obvious drop in hardness.

**Keywords:** CrWN coatings; microstructure evolution; spinodal decomposition; thermal stability; hardness; plasma enhanced magnetron sputtering
