بررسي تاثير همزمان اصلاح سازي سطح و پوشش فورستريت نانو ساختار بر رفتار خوردگي زير لايه فلزي فولاد زنگ نزن

چكيده انگليسي :

91 Effects of Surface Treatments and Nanostructured Forsterite Coatings on the Corrosion Behavior of Stainless Steel Substrates Seyed Naveed Hosseini Nohoji naveed hosseini@ma iut ac ir January 18 2015 Department of Materials Engineering Isfahan University of Technology 84156 83111 Isfahan IranDegree M Sc Language FarsiDr Hamidreza Salimi Jazi Assoc Prof Supervisor E mail hrjazi@cc iut ac irDr Mohammadhossein Fathi Prof Supervisor E mail Fathi@cc iut ac irAbstractType 316L stainless steel is widely used as biomedical implants owing to its high mechanical strength biocompatibility and low cost However they are susceptible to the localized corrosion in the human bodycausing the release of metal ions into the tissues surrounding the implants and subsequent allergens andcarcinogens To improve the corrosion behavior of AISI 316L stainless steel substrates a novelnanostructured forsterite coating was deposited on the stainless steel substrates by electrophoreticdeposition EPD method Pure nanostructured forsterite was synthesized using a mechanical activationroute assisted with heat treatment In order to increase forsterite powders surface charge the synthesizedpowders were then immersed in a slurry containing 0 5 wt Polyvinyl alcohol PVA The suspensionwas prepared by mixing the PVA coated forsterite powders in methanol media and electrophoreticallydeposited onto stainless steel substrate for 1 3 and 5 min under voltages of 10 15 20 and 25 V Depositedcoatings for 5 minutes under 25V was homogeneous and adhesive To preserve the nanometric dimensionof wet coatings they were subjected to a two step sintering process The coatings were crack free andhomogenous exhibiting good adhesion to the substrate Moreover no decomposition of the forsteritecoating was observed after two step sintering Pull off and standard Vickers diamond pyramid indentertests were utilized to evaluate the mechanical properties of the coatings The bioactivity of the preparedspecimens was evaluated in simulated body fluid SBF at 37 C for up to 28 days To assess the generaland localized corrosion behavior of the AISI 316L stainless steel in ringer solution under cyclicpolarization the substrates with different roughness polished grinded up to 400 grit and sandblasted andchemical surface treated in nitric acid 40 vol and sulfuric acid 20 vol and 15 vol wereemployed Considering the radial crack length measurements the fracture toughness of the coating wasobtained 1 18 MPa m0 5 The sandblasted substrate showed the highest cohesive strength 12 6 MPa whilethe lowest one was observed for the polished substrate 6 9 MPa The Fourier transform infraredspectroscopy FTIR energy dispersive spectroscopy EDS and scanning electron microscopy SEM observations of soaked samples confirmed the bone like apatite formation on the nanostructured forsteritecoating after immersing in SBF for 28 days pointing to bioactivity behavior of the coating The corrosiontests indicated that the forsterite coatings act as barrier on the surface and decreased the corrosion currentdensity and increased corrosion potential The coated substrates which were grinded and passivated in 40vol nitric acid and 20 vol sulfuric acid illustrated break down potentials Eb of 652 and 518 mV respectively These values were considerably higher in comparison to those for the uncoated and coated without surface modification samples indicating improvement in localized corrosion resistance Keywords AISI 316L Bioactivity Electrophoretic deposition Forsterite bioceramic Surface treatment

حسيني نهوجي، نويد

بررسي تاثير همزمان اصلاح سازي سطح و پوشش فورستريت نانو ساختار بر رفتار خوردگي زير لايه فلزي فولاد زنگ نزن

فولاد زنگ نزن آستنيتي316ال , بيو سراميك فورستريت , لايه نشاني الكتروفورتيك , زيست فعالي