Slow Crack Growth Behavior of Zirconia‐Toughened Alumina and Alumina Using the Dynamic Fatigue Indentation Technique

Abstract

A dynamic fatigue indentation technique was used to determine the slow crack growth (SCG) parameters of a medical‐grade platelet‐reinforced zirconia‐toughened alumina and two different fine‐grain aluminas: one a common grade of nominal 99.5% purity, and the other a high‐purity (99.94%) medical‐grade alumina. Fatigue tests in bending were performed at various loading rates with precracked Vickers indentations in 100% relative humidity conditions. Inert strength tests were performed in dry nitrogen. The dynamic fatigue analysis accounts for the presence of the indentation. The SCG power law exponent was found to be 36, 65, and 93 for the 99.5% alumina, the 99.94% alumina, and the zirconia‐toughened alumina, respectively. The presence of glassy phase likely increases SCG in the 99.5% alumina compared with the higher purity alumina. The zirconia‐toughened alumina exhibits a relatively steep R curve that forms due to two toughening mechanisms: platelet reinforcement and transformation toughening. It is apparent that neither of mechanisms degrades significantly due to moisture‐assisted SCG.

Ceramics and ceramic coatings in orthopaedics

“…Stress corrosion cracking is a common problem for all polycrystalline ceramics due in part to the presence of grain boundary impurities. Ceramics with fewer impurities are less sensitive [212,345], and grain boundaries that have high nitrogen content show increased resistance to SCG [349,350]. Compositional and microstructural engineering of these advanced ceramics is on-going by many organizations in an effort to reduce their sensitivity to fatigue.…”

“…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.…”

Comportamento de fadiga e perfis de tensões residuais de cerâmicas odontológicas

“…Em um desses estudos, a metodologia de fadiga cíclica resultou em valores de n de 38 [38], enquanto que outros dois trabalhos que usaram a fadiga dinâmica encontraram valores de n de 17 [86] e 28 [84], respectivamente. A diferença entre esses dois últimos valores de n obtidos por meio do mesmo ensaio de fadiga indicam que a geometria do ensaio também parece influenciar o resultado obtido, uma vez que o primeiro estudo utilizou flexão biaxial [86] e o segundo realizou ensaio de flexão em quatro pontos [87].…”