Spraying distance is a relevant parameter in

As expected, the amount of reinforcement into the final coatings increases as the amount of reinforcement into the initial powder blend increases. The other spraying parameters: layers, spraying distance and gun speed, do not present a relevant influence on the incorporation of ceramic reinforcement into the coatings (Fig. 5c and d).
Fig. 5e and f presents the relationship between the porosity with the HVOF parameters (% SiCp in feedstock, spraying distance, number of layers and gun speed) for the two matrices. The horizontal line represents the mean value of the obtained data. Based on the Taguchi DOE method, it Retinyl glucoside can be stated that the porosity value of the Al and Al11Si coatings: (i) decreases as the vol.% SiCp increases; (ii) slightly increases as the spraying distance increases; (iii) slightly increases as increasing the number of layers applied and (iv) slightly increases as the gun speed increases.
The critical parameter in the coating porosity was the vol.% SiCp. The porosity reduction observed as the amount of reinforcement increases may be related with the fact that the kinetic energy of the SiCp promotes the compactness of the coating. The mean value of porosity in the Al11Si coatings is lower than for the Al coating as shown in Fig. 5e and f, 1.9% to 2.4% respectively, because the higher fluidity of the Al11Si in comparison with Al favors the wettability of the splats into the substrate and between the subsequent splats. The Al11Si matrix is more sensitive to spraying conditions.