Mechanical alloying of biocompatible Co–28Cr–6Mo alloy

Abstract

We report on an alternative route for the synthesis of crystalline Co-28Cr-6Mo alloy, which could be used for surgical implants. Co, Cr and Mo elemental powders, mixed in an adequate weight relation according to ISO Standard 58342-4 (ISO, 1996), were used for the mechanical alloying (MA) of nano-structured Co-alloy. The process was carried out at room temperature in a shaker mixer mill using hardened steel balls and vials as milling media, with a 1:8 ball:powder weight ratio. Crystalline structure characterization of milled powders was carried out by X-ray diffraction in order to analyze the phase transformations as a function of milling time. The aim of this work was to evaluate the alloying mechanism involved in the mechanical alloying of Co-28Cr-6Mo alloy. The evolution of the phase transformations with milling time is reported for each mixture. Results showed that the resultant alloy is a Co-alpha solid solution, successfully obtained by mechanical alloying after a total of 10 h of milling time: first Cr and Mo are mechanically prealloyed for 7 h, and then Co is mixed in for 3 h. In addition, different methods of premixing were studied. The particle size of the powders is reduced with increasing milling time, reaching about 5 mum at 10 h; a longer time promotes the formation of aggregates. The morphology and crystal structure of milled powders as a function of milling time were analyzed by scanning electron microscopy and XR diffraction.

Amorphization of Co-base alloy by mechanical alloying

“…In the second mixture, the effect of Mo on the amorphization of Co was studied; in this case, 10% in weight of Mo was MA with elemental Co (according with previous work [12]). Fig.…”

“…Other authors [11] associated the amorphization with modification of the mill parameters, such as the ball-to-powder ratio, the charge volume or the milling time. Previous studies [12] demonstrated that MA is an effective method to obtain non-equilibrium phases in cobalt base alloys and helps to force the solubility and amorphization of different alloys [9,10,13].…”

Application of Harmonic Structure Design to Biomedical Co–Cr–Mo Alloy for Improved Mechanical Properties

“…The Severe Plastic Deformation (SPD), especially mechanical milling of powders, is an effective method to prepare fine-grained materials having extremely high strength. 4,5) However, homogeneous ultrafine grained materials suffer from the problem of extremely low ductility. 6,7) Therefore, it is required to prepare material having high strength and excellent ductility at the same time.…”

Bioactive Co-Cr alloy for biomedical applications prepared by surface modification using self-assembled monolayers and poly-γ-glutamic acid

“…Alloys of this type generally demonstrate high levels of biocompatibility and also possess excellent mechanical properties, including resistance to pitting, wear, high abrasion and crevice corrosion, as well as showing high fatigue strength, malleability and ductility 3,4) . Co-Cr alloys are frequently used in implant materials during joint replacement procedures involving hard tissues, such as tooth and bone, where they come into direct contact with blood, soft tissue and bone 5,6) .…”