50 - Different Mechanical Properties of Sand Blasting on Co-Cr Alloys

Abstract

The purpose of this in study was to determine the influence of the sand blasting on the microstructure and the mechanical properties of cobalt chromium alloys. Thirty Co-Cr metal substrates were fabricated according to ISO 9693-1, by Direct Melting Laser Sintering fabricating technique. One group of ten were sandblasted with 50μm Zinc oxide nanopowder, another group of ten were sandblasted with 250μm and one more group group of ten substrates were left as received without sandblasting at all. On the two fist groups a feldspathic porcelain was placed. Then the specimens were tested for metal-ceramic bond strength with 3-point bend test. The fractured specimens were observed with an optical and scanning electron microscopy in order to define the mode of failure. Also, X-ray diffraction spectroscopy was conducted to determine changes in crystalline phases after fabrication and the 3-point bend test. The first group of the 250μm gave more plasticity to the substrates and observed as more eslastic than th other two groups. The groups with the ceramic coating revealed cohesive bond strength. The metallographic analysis of the after porcelain firing, the after 3-point bend test specimens and the as-received revealed changes in microstructure. Regarding the crystallographic microstructure, the patterns had minor changes among the groups. The profilometry also indicated that the bigger the gridblasting particles made the surface of the substrates smother. The adhesion between the metal substrate and the ceramic layer is not affected by the sandblasting. All of the techniques showed similar results and the modulus of elasticity revealed that the bigger the particle of the sandblasting is the higher the mechanical properties are.