## 3 Results and Discussion
### Wear Behavior  
In this study, ball-on disc test was conducted in order to investigate the wear behavior of the laser remelted FeCrCoNiTiAl0,6 HVOF coating. Furthermore, the HVOF coating was also tested for comparison to investigate the effect of laser remelting on wear behavior. Figure 5 shows the friction coefficients of the coatings during test. The values of the friction coefficient are significantly different. The laser remelted HVOF coating has a much lower friction coefficient than HVOF coating. The decrease of the friction coefficient is related to the microstructure of the coatings. The coating is denser and the coefficient is lower. In wear test, the coatings were cut by an Al2O3 ball. The elimination of the pores and cracks in laser remelted coating can provide a smooth contact interface, thus reducing the friction coefficient. Figure 6 shows the confocal laser scanning microscopy (CSLM) micrographs in a same magnification of the HVOF coating and the laser remelted HVOF coating. The wear track on the HVOF coating is obviously wider and deeper than the laser remelted HVOF coating. The maximum depth of the wear track is 47.7 um for HVOF coating and 24.0 um for laser remelted HVOF coating. The wear rates of the coatings as a function of sliding duration are also shown in Figure 6. The wear rate of the HVOF coating is \(W=4.546\times 10^{-5}\) mm\({}^{3}\)N\({}^{-1}\)m\({}^{-1}\), while the wear rate of the laser remelted HVOF coating is \(W=1.375\times 10^{-5}\) mm\({}^{3}\)N\({}^{-1}\)m\({}^{-1}\). The wear rate decreased significantly due to the laser \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline
**Element** & **O (at.\%)** & **Al (at.\%)** & **Ti (at.\%)** & **Cr (at.\%)** & **Fe (at.\%)** & **Co (at.\%)** & **Ni (at.\%)** \\ \hline
1 & 2.74 & 4.66 & 13.29 & 16.13 & 39.55 & 12.34 & 11.29 \\
2 & 2.67 & 14.1 & 12.43 & 11.35 & 30.36 & 14.42 & 14.66 \\
3 & 20.95 & 35.87 & 9.07 & 5.39 & 15.17 & 6.77 & 6.79 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: EDS point result of the laser remelted HVOF coating. Figure 4: EDS mapping result of the laser remelted HVOF coating. Figure 5: Friction coefficient of the coating. remelting process. As we know, the wear behavior is related to the hardness, the wear rate decreased as the hardness increases. When the HVOF coating was remelted by laser beam, micro-pores and cracks decreased dramatically. The compact microstructure and the precipitate of the Al2O3 phase in the coating led to the increase of hardness. In this paper, the measured hardness of the HVOF coating was \(789\pm 54\) HV\({}_{0.1}\), while the hardness of the laser remelted HVOF coating was \(914\pm 17\) HV\({}_{0.1}\). The surface morphologies of the wear tracks of the as-sprayed and laser remelted HVOF coatings are shown in Figure 7. The grooves are observed obviously on the wear track in both of the coatings. In addition, the debris caused by wear is also recognized. These indicate that the abrasion wear is the main wear mechanism for the laser remelted HVOF coating. The large difference in the hardness between the coatings and counter body caused the abrasion wear. The hardness of Al2O3 counter body amounts to 2055 HV\({}_{0.1}\)[31], which is much higher than the coatings. The harder Al2O3 ball could easily cut the coatings. During the test, the coatings endured high contact pressure and then caused local plastic deformation. Moreover, on the wear track surface of the HVOF coating, splat delamination is observed, which is not observed on laser remelted HVOF coating. Figure 6: Wear rate and confocal scanning laser microscope (CSLM) micrographs of the coatings. Figure 7: Surface morphologies of friction samples of the HVOF coating and the laser remelted HVOF coating. Figure 8 shows the cross-sections of the wear tracks of the HVOF coating and the laser remelted HVOF coating. In the polished cross-section of the HVOF coating, severe splat delamination can be observed, indicating that fatigue wear is another failure mechanism in HVOF coating [26].