Subcritical crack growth behavior of dispersion oxide ceramics

Abstract

Zirconia (Y-TZP) is used as material for components of implants and prostheses because of its high short-term strength. The mechanical long-term reliability, however, is limited for Y-TZP because of hydrothermal aging effects and a pronounced tendency for subcritical crack growth. The hypothesis of this study was that a substantial amount of alumina in a zirconia matrix can help to significantly suppress subcritical crack growth and thereby improve the mechanical long-term reliability. The Weibull parameters as well as the parameters of the subcritical crack growth were determined for Alumina, Y-TZP, and two dispersion ceramics, that is Alumina Toughened Zirconia (ATZ, 20% alumina/80% Y-TZP), and Zirconia Toughened Alumina (ZTA, 75% alumina/25% Y-TZP). The long-term failure probability as a function of service time was predicted for the four ceramics. The parameter n of the subcritical crack growth was approx. 80% higher for ATZ compared to Y-TZP. In consequence, the estimated lifetime revealed a significant better mechanical long-term reliability for ATZ. It can be concluded that tailored dispersion oxide ceramics can address the aging problem of monolithic zirconia. This makes ATZ very interesting for components of joint replacement as well as for dental prostheses and implants.

Ceramics and ceramic coatings in orthopaedics

“…Their purpose is to increase the ceramic's overall resistance to fracture via crack deflection [152,156], which is plausible in principle, but their actual contribution to increased toughness, considering their small volume percentage in the composition, has not been fully verified [210]. For ATZ, where t-ZrO 2 is the matrix and Al 2 O 3 is the minor phase, strength improvements are due to transformation toughening and intergranular crack deflection induced by the presence of the Al 2 O 3 particulates at t-ZrO 2 grain boundaries [211,212]. Dispersion of the Al 2 O 3 and ZrO 2 grains is therefore an important design element of this material.…”

“…Results obviously vary by material, but can also differ due to test conditions and applied stress ratios. Furthermore, the data shown in the Table are inclusive of various environmental conditionsparticularly the presence of moisture [211,212,[343][344][345][346][347][348][349][350][351][352][353][354][355]. Stress corrosion cracking is a common problem for all polycrystalline ceramics due in part to the presence of grain boundary impurities.…”

“…10(b) is a representative microstructure of these types of Al 2 O 3 -ZrO 2 nano-composites. For reference purposes, fatigue testing has been conducted for most of the biomaterials of Table 1a, and the reader is referred to selected publications for Al 2 O 3 [357][358][359][360][361][362], Mg-PSZ [363][364][365], Ce-TZP [366,367], Y-TZP [346,[368][369][370], Ce-and Y-ZTA [212,348,355,371,372], ATZ [211], Si 3 N 4 [344,354,373,374], CoCr [375], Ti6Al4V [376,377], PEEK [378][379][380], and cortical bone [381][382][383].…”

Synthesis, biocompatibility and mechanical properties of ZrO₂-Al₂O₃ ceramics composites

“…Kim et al 7) reported that when Y-TZP was reinforced with addition of 20 vol% Al2O3, exhibited the highest strength and toughness and showed no hydrothermal degradation while aging in an autoclave. Kirsten et al 8) have revealed that a substantial amount of Al2O3 in a zirconia matrix, produces a significant reduction of subcritical crack growth.…”

Fracture load and failure analysis of zirconia single crowns veneered withpressed and layered ceramics after chewing simulation

“…The superior mechanical properties are due to the finer grain size and the tetragonal-monoclinic transformation toughening mechanism of the zirconia which leads to compressive stresses in the material and results in reduced crack propagation 7) . However, some studies reported that the combination of aging and phase transformation has been detrimental for fatigue properties of Y-TZP without veneering 8,9) . Therefore, Y-TZP frameworks should be veneered using either layering technique or overpressed technique.…”