Proceedings of SerbiaTrib '13

c)a)Figure 2: SEM images and microstructuralcharacterization of thermal spray coatings: a) NiCr80/20, b) WC CoCr 18/4 and c) NiCr 80/20+ Cr 2 O 3 .b)Table 3: Results of thermal spray coatings’characterization.Coating Thickness[µm]Porosityvol.%HardnessHV 0,3NiCr 98±16 6.5 359±18WCCoCr 105±15 3.45 1027±21NiCr+Cr 2 O 3 (38+187) ±255.5+10.1 (341+1118)±24As can be observed, the three types of thermalspray coatings present different thickness andporosity. The porosity, acquired by image analysis,is higher for the coatings deposited by APStechnique compared to the HVOF deposits. Thisdifference could be related to both powders sizeand impact velocity, that is lower in APS techniquewith respect to HVOF. Indeed, the difference inkinetic energy of the molten powders, that is higherin HVOF technique, leads to a different density ondeposited coating. The hardness acquired isassociated to the material deposited and the valuesacquired are similar to data available in scientificliterature for thermal spray coatings [1-13].The SEM micrographs obtained on cross sectionof Ni/SiC composite coatings previously etched(acetic acid: nitric acid 1:1) are shown in Fig.3. InTab. 4 are listed the electrodeposited coatings’properties.Table 4: Results of Ni/SiC electrodepositscharacterization.Coating Thickness[µm]SiC wt.%HardnessHV 0.3Ni 78±7 - 172±7Ni/µSiC 73±8 0.8 247±8Ni/nSiC 75 ± 5 0.15 270 ±9Figure 3: SEM images and microstructuralcharacterization of electrodeposited coatings:a) pure Ni, b) Ni/µSiC and c) Ni/nSiC.The microstructure of the electrodeposits iscolumnar. In the case of the pure Ni the metalcolumns are oriented along the direction ofelectrical fields. The addition of SiC micro-particlesleads to a slight modification of the Ni columnsorientation and size. On the other hand, thecodeposition of SiC nano-particles leads to theformation of a fine grained deposit in which the Nicolumns are not oriented. The addition of microparticlesleads to a microstructure columnar with aslight modification of orientation, caused probablyc)13 th International Conference on Tribology – Serbiatrib’13 49