Fatigue Property and Cytocompatibility of a Biomedical Co–Cr–Mo Alloy Subjected to a High Pressure Torsion and a Subsequent Short Time Annealing

Abstract

In the present study, we evaluated the effects of high pressure torsion (HPT) and subsequent short time annealing processing on fatigue properties and cytocompatibility of the biomedical Co–Cr–Mo alloy (CCM). Before processing, CCM was solution treated (CCM_ST) to achieve a microstructure composed of coarse single γ-phase equiaxed grains with no internal strain. Through HPT processing, an inhomogeneous microstructure containing both micro- and nano-scaled grains is obtained in CCM specimens, which were named as CCM_HPT, accompanied by high internal strain and extensive ε martensite. Following a subsequent short time annealing, a uniform single γ-phase ultrafine-grained microstructure with small local strain fields dispersed forms in CCM specimens, which were named as CCM_HPTA. This microstructure change improves fatigue strength in CCM_HPT, and further in CCM_HPTA, because of the enhanced crack initiation and/or propagation resistance. For cytocompatibility evaluation, the cells cultured on CCM_ST show an immobilization tendency, while those cultured on CCM_HPT exhibit a locomotion tendency. The cells cultured on CCM_HPTA have an intermediate pattern. Compared with CCM_ST, much larger numbers of cells are proliferated in both CCM_HPT and CCM_HPTA. All these results demonstrate that the CCM_HPTA offers an improved fatigue property and a good cytocompatibility. Therefore, it is promising for use in biomedical applications.

Fig. 3 EBSD results of CCM_ST,¹³⁾ CCM_HPT, and CCM_HPTA.