## 4 Conclusions  
This research project compared the wear and corrosion behavior of cermet coatings made from conventional WC-Co-Cr and recycled materials. As an alternative recycled cermet, filter dust from an HVOF system was used, consisting mainly of WC-Co and \begin{table}
\begin{tabular}{c c c} \hline
**Sample** & **U\({}_{\text{corr}}\) [mV]** & **i\({}_{\text{corr}}\) [\(\mu\)A/cm\({}^{2}\)]** \\ \hline GC-M1 & \(-401\)\(\pm\) 24 & \(11.0\)\(\pm\) 2.3 \\ GC-M2 & \(-394\)\(\pm\) 21 & \(37.1\)\(\pm\) 3.1 \\ Ref-M1 & \(-171\)\(\pm\) 13 & \(5.9\)\(\pm\) 0.8 \\ Ref-M2 & \(-273\)\(\pm\) 15 & \(6.6\)\(\pm\) 0.7 \\ \hline \end{tabular}
\end{table} 
Table 4: Corrosion current density and corrosion potential. Figure 14: Cross-section SEM image of the GC coating after corrosion in 3.5% NaCl at pH 3.5. WC-Co-Cr, as well as various other components, such as metallic oxides. The recycled powder, belonging to the Green Cermets (GCs) group, was analyzed in terms of particle size distribution and sieved to improve its applicability. The sieving process filtered out significantly coarser particles, resulting in a distribution that approached that of the reference material. However, the sieved GC powder still contained a significant proportion of particles smaller than 10 \(\upmu\)m. This resulted in greater heterogeneity in the microstructure of the coating concerning particle size. SEM/EDX analysis revealed the presence of elements such as Fe, Cr, Ni, Mo, and Al, mostly in oxidized form, in addition to the main component WC-Co-Cr/WC-Co. Investigations of the mechanical properties showed that the hardness of the GC coating was significantly lower than that of the WC-Co-Cr coating. The measured hardness of the GC coating was 678 \(\pm\) 55 HV, whereas that of the reference coating was 1042 \(\pm\) 29 HV. Additionally, critical cracking behavior was identified in the GC coating, with cracks extending well beyond the edges of the Brinell indentation areas. Once again, the heterogeneity of the chemical composition and particle size contributed to the reduced load-bearing capacity. The wear tests indicated that the steady-state coefficient of friction for the GC coatings, at 0.62, was significantly higher than that for the WC-Co-Cr coating, for which the value was only 0.3. However, no measurable wear volume was detected for either coating. The WC wear ball only slid over the exposed carbides in the reference coatings but over carbides and oxides in the GC coatings. The GC coatings exhibited lower corrosion resistance than the WC-Co-Cr coatings, regardless of the medium used. Reducing the pH value increased the corrosion current density of the GC coating from 11 \(\upmu\)mA/cm\({}^{2}\) to 37.1 \(\upmu\)A/cm\({}^{2}\). In contrast, the WC-Co-Cr coatings showed no significant change in the corrosion current density. Even though the SEM images of the GC corrosion samples depicted localized corrosion at the coating surface (pitting corrosion), the interface with the substrate remained unaffected. In general, it can be stated that the performance range of the GC coatings is significantly lower than that of conventional WC-Co-Cr coatings. Nevertheless, the wear and corrosion tests have demonstrated the potential of GCs for industrial applications. Conceptualization, D.W. and J.E. ; methodology, D.W., J.E. and G.M. ; software, D.W.; validation, D.W., J.E., I-D.U. and G.M. ; formal analysis, D.W., J.E., I-D.U. and G.M. ; investigation, D.W.; resources, D.W., J.E., I-D.U. and G.M. ; data curation, D.W.; writing--original draft preparation, D.W.; writing--review and editing, D.W., J.E., I-D.U. and G.M. ; visualization, D.W.; supervision, I-D.U. and G.M. ; project administration, D.W.; funding acquisition, I-D.U. and G.M. All authors have read and agreed to the published version of the manuscript. This research received no external funding. Not applicable. The data in this study is available on request from the authors. The data are not publicly available because they are part of ongoing studies.