PREPARATION OF BIOACTIVE Ca-P COATING ON Ti ALLOY AND MEASUREMENT OF ITS ADHESION BY SCRATCH TEST
Abstract
Many research works in field of biomaterials are focused on forming of the bioactive coatings on metallic and non-metallic substrates which are implanted into human body. The purpose of the effort of this combination is the utilizing the mechanical properties of substrate and the bioactivity of the coatings. Implants with bioactive coating interact faster with living body and make a strong bond with the tissue. For the coating it is very important to have a very good adhesion to the substrate. Better bonding of implants to tissue can by achieved by mechanical and chemical treatment of the implant surface before the deposition.
This work is focused on preparation of calcium-phosphate (Ca-P) coating on ground and sandblasted titanium alloy Ti6Al4V in calcification solutions and on the measurement of adhesion of these coatings to substrates.
Substrates were pretreated by concentrated HCl and then by solution of 10 mol.dm-3 NaOH. The sodium titanate hydrogel is formed on the surface of substrate. The uniform Ca-P coating of densely clustered octacalcium phosphate (OCP) crystals is formed after 2 hours of exposition in calcification solution (SCS). The adhesion of this Ca-P coating on grinded and sandblasted titanium alloy was measured by scratch method using a scratch tester. The coatings were visually observed by scanning electron microscope (SEM/EDS) and optical microscope (OM).
Coatings formed in two hours in SCS had a good adhesion at low load and they peeled at medium load. The substrates damaged at high load. Ca-P coatings formed in three days in SCS solution had a poorer adhesion to substrate, which had been negatively influenced by size of OCP crystals and cracking of thick film of Ca-P compounds.
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