Tailoring the chemical composition and microstructure of CrxN deposited by HiPIMS through duty-cycle modifications

Abstract

The development of homogeneous, dense, and smooth hard coatings is a challenging task, and that is why the high power impulse magnetron sputtering (HiPIMS) method has been proposed to tailor and control the microstructure through the modification of the duty cycle. HiPIMS offers extensive possibilities to obtain good quality films with fine and dense morphology. In this work, the synthesis of Cr x N coatings by HiPIMS with the variation of duty cycle (τ = 2.7% and 12%), substrate bias voltages (V b = −150 and − 250 V), and gas ratio ( f N 2/ Ar = 0.2 and 0.4) was evaluated. The influence of these processing conditions on the chemical composition, microstructure, and adhesion of HiPIMS Cr x N was investigated. A significant increment of the deposition rate and the chromium content in the Cr x N coatings is observed at τ = 12%; meanwhile, at τ = 2.7%, films showed high nitrogen content. The crystalline phases like α-Cr + h-Cr 2 N, h-Cr 2 N, and h-Cr 2 N + c-CrN were identified in the as-deposited films. The Cr-rich coatings presented faceted columns with cauliflower-like surface morphology , while the growth of the h-Cr 2 N phase caused a grain size refinement and a denser microstructure. The surface morphology of the h-Cr 2 N coatings changed from pyramidal to stacked pyramids with the reduction of the duty cycle. The transformation of the h-Cr 2 N to c-CrN leads to highly dense columnar microstructures with a fine granular morphology and a smooth surface. The duty cycle strategies can be applied to develop a particular microstructure with specific chemical composition and crystallographic phases, resulting in an alternative method to produce graded or multilayer systems. The duty cycle reduction increases the interfacial adhesion strength of the coatings. • Duty cycle modifies composition, phases, microstructure, and morphology. • Higher duty cycle enhances target current and coating deposition rates. • Duty cycle strategy is a good option to deposit graded or multilayer systems.