Adhesion of new bioactive glass coating

A valuable alternative to the existing biomedical implant coatings is a bio active glass (BAG) coating that is produced by reactive plasma spraying. A mechanical performance requirement that is of the utmost importance is the adhesion strength of the coating. Considering the application as dental imp lant, a new adhesion test (shear test), which was close to the service cond itions, was designed. A Ti6A14V rod (O3 mm) with a sprayed BAG coating of 5 0 mu m was glued with an epoxy glue to a hollow cylindrical counterpart and was used as such in the tensile machine. This test was evaluated by finite element analysis (FEA). Preliminary experiments showed that a conversion f rom shear to tensile adhesion strength is possible by using the Von Mises c riterion (sigma = 3(1/2)tau), indicating that thin coatings of brittle mate rials can behave as a ductile material. The new coating technique was prove d to produce a high quality coating with an adhesion strength of 40.1 +/- 4 .8 MPa in shear and 69.4 +/- 8.4 MPa in tension. The FEA revealed that no o ne homogeneously distributed shear stress is present but several nonhomogen eously distributed stress components (shear and tensile) are present in the coating. This analysis indicated that real service conditions are much mor e complicated than standard adhesion tests. (C) 1999 John Wiley & Sons, Inc .