Grit Blasting Effects on Mechanical Properties of Ceramic Coated CoCr-alloy

Objectives: The objective of the present work is to compare the effect that grit blasting with two different particles size produces on the microstructure and mechanical properties of the CoCr substrate and also in the metal-ceramic interphase.
Methods: 16 rectangular specimens of CoCr alloy fabricated by DMLS (from Eyyunan) have been cut (20×3×1 mm) and each half of them have been blasted with alumina particles of 50 and 250 µm respectively, which yields to two different surface roughness. Consecutively a ceramic layer has been added following the conventional commercial procedure. Three-point bending tests with a micromachine adapted to an scanning electronic microscope (SEM) have been performed.
Results: In all cases, as it can be appreciated in Fig. 1, the cracks progress through the ceramic layer and not in the metal-ceramic interfaces, leaving rests of ceramic adhered to the metal. The mode of fracture seems to be fragile, as it can be expected for a dissimilar joint in which one adherend is a ceramic material. Concerning to CoCr substrate, measurements show that samples with higher roughness present a higher flexural strength and a more brittle behavior than the less rough ones.
Conclusions: Grit blasting process, apart from increasing surface roughness, induces changes in the sub-superficial microstructure and compressive residual stress in the surface of CoCr alloy. Grit blasting with bigger particles produces a higher work hardening effect on CoCr substrate and the mode of fracture between ceramic layer and CoCr alloy seems to be fragile