Structural disordering in WC thin films induced by SiC additions

Abstract

An investigation has been conducted into the structural disordering in WC thin films induced by SiC additions. The effect of this disordering on film hardness is also reported. In this investigation, WC-SiC films with a SiC content varying from 11.6 to 38.2 pct were deposited using dual rf magnetron sputtering. The relative Si and W content in the films was determined using electron microprobe analysis. Analysis by X-ray diffraction (XRD) confirmed that, within this compositional range, the film structure transformed from crystalline to amorphous. The XRD patterns showed that the crystalline films consisted primarily of WC 1Ϫx , along with a small amount of W 2 C; no clear evidence for a separate crystalline SiC phase was found. High-resolution transmission electron microscopy (HRTEM) studies showed that with a lower Si content, the films consisted of crystallites 3 to 5 nm in diameter embedded in an amorphous phase. As the Si content increased, the amorphous phase content increased, both as interlayers between crystallites and as particles within the crystallites. Further Si increases led to a structure consisting of a high density of interconnected amorphous particles within well-defined semicrystalline domains separated by a thin amorphous interlayer. At the highest Si content, a clear two-phase morphology evolved, consisting of two nearly amorphous but distinct phases, which suggests a fine-scale partial-phase separation between the WC and the SiC. At the atomic level, it was found that Si decreased the coherence length within the crystalline phase, resulting in a structure of mixed crystalline/highly disordered phases scaled in the range of 2 to 4 nm. Despite the significant alterations in the film structures due to SiC additions, the hardness and modulus of the films were essentially constant within the compositional range of the transition, although films with SiC contents of less than ϳ11 pct had significantly lower hardness levels. It is proposed that the effects of Si on hardness can be explained in terms of competition between the percolation threshold and the amorphization-inducing effect of Si.

Effects of Zr, Nb, or Si addition on the microstructural, mechanical, and corrosion resistance of TiCN hard coatings

“…The addition of Nb or Zr determined a slight variation of d around the value observed in the reference coating. As expected, the addition of Si to TiCN has determined the decrease of the grain size mean value, due to the formation of amorphous phases (Si, SiN x , SiCN) at the grain boundaries, which hinders the crystallite development, as also reported in the literature [48,49]. We do not expect the formation of a-SiC because its energy of formation is much larger than the one of SiN x .…”

Phase transformation of high temperature on Fe–Al–Mn–Cr–C alloy

“…Hence, Fe-Al-Mn-C alloys are suitable for industrial use and in biomedical applications. The typical chemical compositions of Fe-Al-Mn-C alloys are in the ranges of Fe-(4.9-11.0) mass% Al-(23.7-35.0) mass% Mn-(0.5-1.5) mass% C [8][9][10][11][12]. Furthermore, it is generally concluded that Fe-Al-Mn-C alloys exhibit good oxidation resistance at high temperatures because a composition of Al between 8.5 wt.% and 10.5 wt.% results in the formation of a continuous protective Al 2 O 3 layer on the surface of the alloys [13][14][15].…”

On the Microstructure and Properties of a High Al-Alloyed 100Cr6 Steel

“…However, long time tempering of these alloys yields a needle‐shaped κ‐phase at 300 °C . The κ‐phase is observed to dissolve at temperatures around 900 °C …”

“…[25] The k-phase is observed to dissolve at temperatures around 900 8C. [24,26,27] Because of the larger atomic radius of Al compared to Fe, the former leads to solid solution strengthening: yield strength increase of 20 MPa per 1 at% Al has been observed. [20,26] Moreover, due to the larger atomic radius of Al and its lower molar weight compared to Fe, 1.3% weight reduction is expected per 1 wt% of Al.…”