Fatigue limit of polycrystalline zirconium oxide ceramics: Effect of grinding and low-temperature aging

Effect of Grinding and Multi-Stimuli Aging on the Fatigue Strength of a Y-TZP Ceramic

“…It is already known that grinding leads to an increase in roughness (12,13), however an extensive number of studies have been showing that the phase transformation toughening mechanism may counterbalance to some extent this effect closing this defects and even resulting in increased flexural strength (3,12,13,19). Our data support the aforementioned statement, since no negative influence of increased roughness (grinding) on fatigue strength.…”

“…For this procedure it was used a biaxial flexural assembly (piston-on-three-balls according to ISO-6872:2008) in an electro-dynamic fatigue simulator (Instron Electro Puls E3000, Instron Corporation, Norwood, Massachusetts, USA; maximum estimated error 0.5% from the maximum load cell capacity, as we used a 5 KN load cell, it would be expected a maximum error of 25 N) under 10 6 cycles with 20 Hz frequency and a ranging load of 20 N (minimum applied load during cycle) to the maximum of 50% of the mean (C= 432.95; CA= 490.05; G= 538.45; GA= 415) biaxial flexural strength observed in a previous study that considered each evaluated condition on same material under a biaxial flexural static test assembly (12).…”

“…On this sense, to the authors knowledge, there are only two studies on literature that considered the fatigue behavior of aged Y-TZP ceramics: Cotes and collaborators (7) did not notice any damaging effect on mechanical properties even after 15x10 6 cycles at 200N; and Pereira and collaborators (12) found congruent finding, i.e. no deleterious effect even when applying an accelerated fatigue strength test.…”

“…defining the final outcome: if the balance tends to the introduction of defects it may be observed a negative impact (8,9,24), while if the balance favors phase transformation it could be observed the toughening mechanism (12,13,19). Our study corroborates that assumption, since we used the methodology preconized by this systematic review (14) to avoid defect introduction (handpieces coupled to slow speed motors and the use of plenty coolant) and we did not notice a deleterious effect, even using coarse diamond burs during grinding.…”

“…Those adjustments will lead to t → m phase transformation and also to the introduction of defects (11)(12)(13). On this sense, literature shows that the outcome (toughness mechanism or LTD) will depend on the balance between these two factors: phase transformation and introduction of defects (14).…”