# A New Plasma Surface Alloying to Improve the Wear Resistance of the Metallic Card Clothing
## 4 Conclusions  
In this work, we report a new surface strengthening process (double glow technology) to improve the wear resistance of the metallic card clothing. The chromizing coating was successfully prepared on the metallic card clothing through the double glow technology. The surface morphologies microstructure and phase composition were characterized by the scanning electron microscopy (SEM), energy disperse spectroscopy (EDS) and X-ray diffraction (XRD) method. The hardness was examined by Vickers hardness test and nano-indentation test. The effects of different sliding speeds on the friction properties of metallic card clothing were studied. The following conclusions can be drawn from this study.  
(1) The surface of the chromizing coating is smoother without granular sediment. The bond between the chromizing coating and metallic card clothing was a metallurgical, which guarantees it high adhesion between coating and metallic card clothing. The whole thickness of coating was approximately 7 \(\upmu\)m.  
(2) The hardness of metallic card clothing increased obviously after plasma surface alloying. The average value of hardness was 564.9 HV\({}_{0.05}\), which was approximately 1.55 times the metallic card clothing hardness value. The H/E ratio and the H\({}^{3}\)/E\({}^{2}\) ratio of the chromizing coating were approximately 2.5 times and 12 times the metallic card clothing ratios, which account for the significantly lower specific wear rate of chromizing coating compared to the metallic card clothing.  
(3) The wear resistance of metallic card clothing was obviously improved after strengthening by double glow technology. The specific wear rates of metallic card clothing after plasma surface chromizing were 2.91, 3.30, and \(2.95\times 10^{-4}\).mm\({}^{3}\).N\({}^{-1}\).m\({}^{-1}\), which was significantly lower than the wear rate of metallic card clothing before plasma surface chromizing.  
Figure 9: Wear track morphology of chromizing coating under various sliding speeds (**a**) 2 m/min; (**b**) 4 m/min; and (**c**) 6 m/min.  
(4) Double glow plasma surface metallurgy technology is easy to operate, stable in process parameters and suitable for mass production of metal card clothing. The chromizing coating processed by the double glow technology provides a solution to strengthening the wear resistance of the metal card clothing.  
Conceptualization: D.W., F.L.; Methodology: S.L. and X.C.; Data curation, D.W., P.Z., Z.W.; Formal analysis, F.L.; Investigation, S.L.; Methodology, S.L., X.C.; Software, F.D; writing--original draft preparation, D.W.; writing--review and editing, D.W., F.L.  
This project was supported by Natural Science Foundation for Excellent Young Scientists of Jiangsu Province, China (Grant No. BK20180068), China Postdoctoral Science Foundation funded project (Grant No. 2018M630555), the Fundamental Research Funds for the Central Universities, China (Grant No. NS2018039), Opening Project of Key Laboratory of Materials Preparation and Protection for Harsh Environment (Nanjing University of Aeronautics and Astronautics), Ministry of Industry and Information Technology (Grant No. NJ2018009), Opening Project of Jiangsu Key Laboratory of Advanced Structural Materials and Application Technology (Grant No. ASMA201701).  
The authors declare no conflict of interest.