Evaluating sol-gel ceramic thin films for metal implant applications. II. Adhesion and fatigue properties of zirconia films on Ti-6Al-4V

Abstract

The degree to which ceramic coatings or thin films applied to bone-interfacing metallic implants can improve the overall performance of these implants with respect to implant fixation, wear, or corrosion relies especially on the response of these films to loading. In this study, the adhesion and fatigue properties of sol-gel zirconia films that could be reproducibly deposited onto polished Ti-6AI-4V substrates was investigated. For zirconia films on the order of 100 nm thick, a shear lag-based strain approach indicated a shear adhesion strength of approximately 275 MPa. Small variations in film thickness and substrate surface preparation had little effect on this adhesion, which was believed to be due to alkoxide molecule interactions with free hydroxyl groups on the substrate surface as well as some limited interfacial diffusion following the 500 degrees C anneal. Subsequent fatigue testing of these films in air using novel tapered rotating beam fatigue samples demonstrated their excellent fatigue characteristics, with films surviving up to 10(7) cycles, the endurance limit of the Ti-6AI-4V (approximately 635 MPa). Overall, the exceptional mechanical properties of this ZrO2/Ti-6AI-4V system along with the inherent advantages of sol-gel processing support continued studies to utilize this technology for implant surface modification.

Indentation and Fracture of Hybrid Sol-Gel Silica Films

“…As a complement to nanoindentation testing, micro-mechanical tensile testing is valuable in elucidating the critical conditions for cracking and debonding of thin brittle films on ductile substrates (Ignat, 1996;Ignat et al, 1999). These types of experiments have been shown to offer insights into evaluating interfacial adhesion of thin films and multilayered structures (Agrawal & Raj, 1989;Filiaggi et al, 1996;Scafidi & Ignat, 1998;Wang et al, 1998;Harry et al, 2000;Latella et al, 2007a;Roest et al, 2011).…”

Mechanical integrity of thin inorganic coatings on polymer substrates under quasi-static, thermal and fatigue loadings

“…800,000 cycles. The existence of a threshold strain (detected for zirconia films [72] but absent for bulk metals and Al films [61]) was not investigated. It would be lower than 40% of the COS and would correspond to an endurance limit well beyond 10 5 cycles for the ITOA coating.…”

Evaluating interface strength of calcium phosphate sol–gel-derived thin films to Ti6Al4V substrate

“…Substrate straining tests have been used to investigate the mechanical behavior and bonding of thin brittle films with ductile substrate materials [3][4][5][6][7][8][9][10][11][12][13][14][15][16]. In these tests, tensile force is applied to the more ductile substrate causing transverse crack development in the more brittle coating overlayer.…”

“…In the present study, we applied a substrate straining test and shear lag analysis method for evaluating the interface shear strength of Ti6Al4 V samples with thin sol-gel-formed Ca-P films made using either inorganic or organic precursor solutions. We have used this test method previously for determining the interfacial shear strength of sol-gel-derived ZrO 2 films on Ti6Al4 V [12] and stainless steel [14,15] substrates. As reported elsewhere [1,2], we are investigating these HA films as coatings to increase the rate of bone ingrowth into porous-surfaced Ti6Al4 V implants.…”