Annealing effect on the hydrophobic property of Cr2N coatings

Cr–N coatings were deposited in Ar/N2 plasma at various nitrogen flow rate ratios by using the reactive magnetron sputtering process. The solid solution Cr(N), chromium nitride Cr2N and CrN were found to form at nitrogen gas flow rate ratios of 8%, 32% and 48%, respectively. The hydrophobic property of these three phases was studied by water contact angle (WCA) measurement. The Cr2N phase with higher WCA was further selected to study the high temperature oxidation and the hydrophobic properties. The Cr2N coatings were annealed in air for 2 h between 300 and 900 °C at 100 °C interval, respectively. The experimental results show that WCA of the as-deposited Cr2N is about 106° and there is no obvious change when annealed below and at 500 °C. As the annealing temperature increased to 700 °C, WCA increased to 115° with rougher surface and retained Cr2N. After annealing at 900 °C, the rough crystalline Cr2O3 covers the surface and roughness sharply increases to 57 nm. WCA also rapidly drops down to 28°.