# A New Plasma Surface Alloying to Improve the Wear Resistance of the Metallic Card Clothing
## 3 Results and Discussion
### Nanoindentation Tests  
The wear resistance of materials always depends on the material hardness. Consequently, a high hardness could effectively improve the wear resistance of materials [18]. In recent years, some researchers considered that the hardness and elastic modulus ratio also constitutes a parameter for the material wear resistance measurements. The H/E was the resistance of elastic strain to failure and the H\({}^{3}\)/E\({}^{2}\) represented the resistance to plastic deformation of the material [19]. A high H/E could improve the wear resistance and the fatigue resistance [20]. Force-depth curves of uncoated and coated samples are shows in Figure 6a. The results of nanoindentation testing demonstrated that the coating had a significant effect on the mechanical properties of metallic card clothing. The nanohardness and elastic modulus could be calculated through the force-depth curves and the Oliver-Pharr method [13; 15]. Additionally, the results are presented in Figure 6b. The nanohardness (H) value of the metallic card clothing was 3.41 GPa; the nanohardness (H) value of the chromizing coating was 6.36 GPa, which was approximately 1.87 times the metallic card clothing nanohardness value. The elastic modulus (E) of the metallic card clothing was 161 GPa and the elastic modulus (E) of the chromizing coating was 118 GPa, which was lower compared to the metallic card clothing. Due to the ion sputtering effect, the deposition layer could be divided into the external gassy surface layer and the internal compact texture layer [8]. The external gassy surface layer of the deposition layer surface led to the lower elastic modulus of the chromizing coating compared to the metallic card clothing. The H/E ratios of the metallic card clothing, and the chromizing coating were \(2.12\times 10^{-2}\) and \(5.38\times 10^{-2}\), respectively. The H\({}^{3}\)/E\({}^{2}\) ratios of the metallic card clothing and the chromizing coating were \(1.53\times 10^{-3}\) and \(1.85\times 10^{-2}\). Figure 6: Nano indentation curve, nanohardness and elastic modulus bar graph of the metallic card clothing before and after plasma surface alloying. (**a**) Force-depth curves of uncoated and coated samples, and (**b**) hardness and elastic modulus of uncoated and coated samples. \begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline \multirow{2}{*}{**Sample**} & **Test** & \multirow{2}{*}{**1**} & \multirow{2}{*}{**2**} & \multirow{2}{*}{**3**} & \multirow{2}{*}{**4**} & \multirow{2}{*}{**5**} & \multirow{2}{*}{**Average Value**} \\  & **Point** & & & & & & & \\ \hline \multirow{2}{*}{The Metallic Card} & a & 451.3 & 458.7 & 462.8 & 478.1 & 476.6 & 475.5 & \\  & b & 328.2 & 352.6 & 334.2 & 320.5 & 324.8 & 342.8 & 365.4 \\  & c & 301.1 & 319.4 & 324.2 & 318.3 & 326.4 & 317.9 & \\ \hline \multirow{2}{*}{After Plasma Surface} & a & 549.3 & 552.8 & 574.5 & 569.7 & 577.7 & 564.8 & \\  & b & 546.8 & 567.9 & 553.6 & 584.5 & 566.8 & 564.3 & 564.9 \\ \multirow{2}{*}{Alloying} & c & 576.9 & 556.3 & 546.5 & 578.5 & 570.4 & 565.7 & \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Results of microhardness test for the metallic card clothing before and after plasma surface alloying (HV\({}_{0.05}\)). Sliding Friction Behaviors of the Metallic Card Clothing Before and After Plasma Surface Alloying under Various Sliding Speeds at Room Temperature  
The friction coefficients versus the sliding distances of the metallic card clothing before and after plasma surface alloying under various sliding speeds are presented in Figure 7a-c. The friction coefficient fluctuation improved with the sliding speed increase. The heat generated during friction was the reason for the changes of organization, structure, roughness of surface with the sliding speed increasing, which accordingly led to changes of the friction coefficient [21]. Figure 7d presents the friction coefficient variation curve of the samples along with sliding speeds.