Effect of N 2 flow on the structure and mechanical properties of (CrTaTiVZr)N x coatings processed by reactive magnetron
- PDF / 898,973 Bytes
- 11 Pages / 584.957 x 782.986 pts Page_size
- 90 Downloads / 178 Views
Du-Cheng Tsai and Erh-Chiang Chen Department of Materials Science and Engineering, National Chung Hsing University, Taichung 40227, Republic of China (Received 6 November 2014; accepted 10 March 2015)
(CrTaTiVZr)Nx coatings were deposited via reactive radio frequency magnetron sputtering. The effects of N2 flow at 0–8 SCCM on the chemical composition, microstructure, and mechanical properties of the films were investigated. The coatings deposited at a N2 flow of #2 SCCM showed a featureless structure with an amorphous phase. When the N2 flow was at 4 SCCM, two distinct layers were observed, namely, the bottom layer (close to the substrate) with an amorphous structure and the top layer with a fibrous structure and face-centered cubic phase. When the N2 flow was further increased, the structure was converted from fibers to columns with larger grains. Accordingly, the maximum hardness value of 36.4 GPa was achieved at a N2 flow of 4 SCCM, thereby indicating that (CrTaTiVZr)Nx coatings may be suitable as hard protective coatings.
I. INTRODUCTION
The development of high-entropy alloy (HEA) has received significant worldwide attention because of the good mechanical properties1 and corrosion resistance2 in the formation of alloys. Yeh et al. introduced the concept of HEA,1 which uses multiprincipal element (at least 5) alloys to replace only one principal element in traditional alloys, such as steel, bronze, and aluminum alloys. In doing so, neither one nor two dominant principal elements affect the properties of HEAs. Surprisingly, HEAs tend to form simple face-centered cubic (FCC) and/or body-centered cubic solid solution phases compared with intermetallic compounds.3 This finding was intuitively attributed to high mixing entropy because thermodynamically speaking, high entropy decreases the Gibbs energy of solid solutions at elevated temperatures to obtain phase selection against intermetallic compounds.4 The severe lattice distortion caused by the incorporation of multiprincipal elements renders the formation of nanosized and amorphous structures.5,6 HEAs demonstrate enhanced strength combined with good resistance to oxidation and corrosion.1–3 As a result, more researchers have agreed with the HEA concept, thereby promoting further investigation on this field of study. The alloy and nitride coatings of HEAs have been manufactured as protective coatings via magnetron sputtering system because of their superior physical properties. To increase their hardness, high-entropy nitride coatings Contributing Editor: Yang-T. Cheng a) Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/jmr.2015.79 924
J. Mater. Res., Vol. 30, No. 7, Apr 14, 2015
http://journals.cambridge.org
Downloaded: 25 Nov 2015
with strong nitride-forming elements like AlCrTaTiZr7 and TiVCrZrHf8 were developed. The nitride coatings not only had increased the hardness of up to 48 GPa but also had only a single NaCl-type phase. Moreover, octonary nitride like AlMoNbSiTaTiVZr nitride9 was used to amplify high entropy effects. An all
Data Loading...
