Figure 10. Stereomicroscopy
showing the secondary cracks on the coating surface, closer to the
fracture plane, after fatigue fracture.
Conclusion
The present study evaluates the fatigue performance of the coatings
given by particles of Cr3C2 and NiCr,
both in nanometric scale, micrometric scale and a combination of 50 %
of both, sprayed by the HVOF technique on ASTM A516 steel substrate. The
study allows the following conclusions:
- The surface roughness of the Nano coating was significantly lower than
both the other coatings. However, the three different layers tested
did not experience significant differences in their fatigue
performance.
- The layers deposition parameters promoted layers whose fatigue
performance does not overcome the fatigue performance of uncoated
substrate.
- HEM method allowed Cr3C2-25NiCr powder
to reach the nanometric size, tending to saturation of 15 nm after 5
hours of milling.
- The microstructural refinement of the splats is in accordance to the
size of the particles spraying. The Nano coating shows more refined
microstructure.
- The layer’s thickness, hardness and porosity did not present
significant differences in relation to the type of coating.