Influence of the Deposition Process on the Cr2alc Phase Formation During Heat Treatment of Cr-Al-C Thin Films

Influence of the deposition process and substrate on microstructure, phase composition, and residual stress state on as-deposited Cr-Al-C coatings

“…The (Cr,Al) 2 C solid solution originates from the hexagonal Cr 2 C phase (space group P6 3 /mmc, prototype Mo 2 C [21]), where both Al and Cr are randomly distributed at the Cr-sites (Wyckoff position 2c -1/3,2/3,1/4) [19,41]. The (Cr,Al) 2 C x phase is described as disordered Cr 2 AlC with the same space group and prototype as (Cr,Al) 2 C. However, the disordered state is not described in more detail in [22] and no information is given on whether the Al and Cr atoms share the same positions in this unit cell as described for (Cr,Al Additionally, only the dis.-Cr 2 AlC phase was determined for the amorphous to Cr 2 AlC phase formation during the P07 experiments, thus it is likely that the phase found by Abduhlkadhim et al [22] during the phase formation is not the proposed (Cr,Al) 2 C x with a small unit cell but the newly found dis.-Cr 2 AlC phase [26]. For more information on that topic, the reader is referred to the second paper [26].…”

“…Those are the result of the higher Cr content, measured for amorphous areas in the asdeposited state (see Table 4). A further discussion of these results is given in the second paper of the series [26] to keep this part focused on the as-deposited state.…”

“…Therefore, with the careful analysis of the temperature steps concerning the different stress origins, qualitative analysis is possible and can give insight into the as-deposited residual stress state. It turned out, that the newly found dis.-Cr 2 AlC phase -briefly described in Section 3.2 and discussed in detail in the second paper of the series [26] -is present in the temperature range suitable for the stress analysis, therefore a brief overview of the dis.-Cr 2 AlC formation is given in the following Section 3.3.2.…”

“…After cooling to 100 °C, the results showed the expected substrate dependency. Even though the CTE for dis.-Cr 2 AlC is unknown, it can be assumed that the CTE for this phase has to be similar to Cr 2 AlC with a Cr 2 AlC RT ¼ 12:5 Á 10 À6 K À1 [63] because both phases are only distinguished by slightly different lattice parameters and shifted Cr-and/or Al-sites [26]. As a result of the hindered contraction of the coatings on the WC-Co substrate, the development of tensile residual stress can be observed parallel to the surface.…”

“…In addition, emphasis is on the discussion of the mechanisms behind the different influences on the coating properties. The investigations in this paper are continued in a second paper [26], which investigates the influence of the as-deposited state on the Cr 2 AlC phase formation during heat treatment of a selection of the coating-substrate combination discussed in this paper.…”