Influence of Boron Additions and Heat Treatments on the Fatigue Resistance of CoCrMo Alloys (original) (raw)
Related papers
Wear, 2011
Metal-on-metal (MOM) hip prosthesis bearings have enjoyed renewed popularity, but concerns remain with wear debris and metal ion release causing a negative response in the surrounding tissues. Further understanding into the wear and corrosion mechanisms occurring in MOM hips is therefore essential. The purpose of this study was to evaluate the tribocorrosion behaviour, or interplay between corrosion and wear, of a low-carbon CoCrMo alloy as a function of loading.. The tribocorrosion tests were performed using two tribometer configurations. In the first configuration, "System A", a linearly reciprocating alumina ball slid against the metal flat immersed in a phosphate buffer solution (PBS). In the second configuration, "System B", the flat end of a cylindrical metal pin was pressed against an alumina ball that oscillated rotationally, using bovine calf serum (BCS) as the lubricant and electrolyte. System B was custom-built to emulate in vivo conditions. The tribocorrosion tests were performed under potentiostatic conditions at-0.345 V, with a sliding duration of 1800 seconds and a frequency of 1Hz. In System A, the applied loads were 0.05, 0.5, and 1 N, in System B, the applied loads were 16, 32, and 64 N (515, 650, and 815 MPa). Electrochemical impedance spectroscopy (EIS), the double layer capacitance and polarization resistance were estimated. The total mass loss (Kwc) in the CoCrMo was determined. The mass loss due to wear (Kw) and that due to corrosion (Kc) were determined. The dominant wear regime for the CoCrMo alloy subjected to sliding changes from wear-corrosion to mechanical wear as the contact stress increases An attempt was made to compare both system, in their tribochemical responses and formulate some insights in total degradation processes. Our results also suggest that the proteins in the serum lubricant assist in the generation of a protective layer against corrosion during sliding. The study highlights the need of adequate methodology/guidelines to compare the results from different test systems and translating in solving the practical problems WEAR_0461, Runa et al-Tribocorrosion Behaviour of CoCrMo Alloy for Hip Prostheses as a function of Loads: A Comparison between Two Testing system
Cobalt-based alloys are extensively used in orthopedic applications for joint replacements due to their wear and corrosion resistance. Corrosion, however, is often associated with fatigue failure in these orthopedic devices. In this study, the effect of boron addition on the corrosion behavior of CoCrMo alloys was studied using linear polarization resistance, potentiodynamic polarization curves, electrochemical impedance spectroscopy, and cyclic voltammetry. The samples were analyzed under as-cast and heat treatment conditions after 21 days of immersion in phosphate-buffered saline (PBS) solution at 37 • C. The boron addition increased the particle content, while the heat treatment promoted enlargement and even distribution of the precipitates throughout the structure. The corrosion resistance was improved by both boron and heat treatments. The best performance was observed for a heat-treated alloy having a very small amount of boron, which had an increased resistance to corrosive attack. Such behavior was attributed to the homogenized microstructure achieved by boron and heat treatment that helped to form a stable passive layer of chromium oxide which endured the 21 days of immersion.
Metals, 2021
The present study evaluates the effect of boron additions on the tribological performance of CoCrMo alloys. The alloys were prepared with boron ranging from 0.06 to 1 wt%. The materials were characterized using metallographic techniques, scanning electronic microscopy, and roughness and hardness tests. Tribological evaluation was made by means of ball-on-disc tests for sliding distances of 4, 8 and 12 km. The samples were in the as-cast condition and after a heat treatment at 1200 °C for 1 h, finished by water quenching. The results showed that wear resistance was influenced by the microstructure and the number of secondary phases. The volume loss decreased as the boron content increased. Due to hard phases, abrasion wear was observed. Delamination fatigue was also detected after long sliding distances. Both wear mechanisms diminished in higher boron content alloys.
Effect of recasting on the useful properties CoCrMoW alloy
2014
The recasting of previously casted alloy is a routine procedure used in dental laboratories in order to reduce the cost of permanent partial dentures. The prosthetic “scrap” encompasses the residuals generated in frame dentures casting process e.g. originating from the runners, from casting cones and improperly completed melts e.g. withmisruns, shrinkage porosities and cracks and is frequently used as a part of charge for recasting [20]. The state of load occurring in oral cavity in course of mastication process is diversified and causes various level of stress concentration in hard tooth tissues and in dental fillings which may result in damages of denture fasteners or in ceramic phase separation from prosthetic apparatuses with permanent porcelain veneers [5, 21]. The addition of 50% recast material to a brand new alloy is allowed by greater part of dental alloys manufacturers. Some manufacturers established the condition that the addition of so called scrap can be recasted only o...
We significantly improved the fatigue properties of an electron beam melting (EBM)-fabricated biomedical Co-Cr-Mo alloy by a simple post-production heat treatment without any deformation process. The fatigue properties were improved by transforming the as-EBM-fabricated dual-phase structure (containing both the ε-hcp and γ -fcc phases) into the dominant ε-hcp phase structure, and they were further improved significantly by reverse transforming it into the dominant grain-refined γ -fcc phase structure at certain ageing conditions. It provides an accessible avenue for improving the mechanical properties of additive-manufactured metallic components.
Materials Science, 2019
CoCrMo alloys, which are well-known Co-based biomedical alloys, have many different types of surface integrity problems reported in literature. Residual stresses, white layer formation and work hardening layers are some those, matters which occur as a microstructural alteration during machining. Therefore, such problems should be solved and surface quality of end products should be improved. In this paper, the surface quality of CoCrMo alloy used in tibial component of the knee prosthesis produced by means of turning was investigated. An improvement was suggested and discussed for the improvement in their machinability with the developed turning-grinding method. Finite element analyses were also carried out to calculate temperature and thermal stresses distribution between the tool and the tibial component. The results showed that many parameters such as cutting speed, feed rate, depth of cut, tool geometry, and tool wear affect the surface quality of workpieces of CoCrMo alloy. In ...
Fatigue characteristics of a biomedical β-type titanium alloy with titanium boride
Materials Science and Engineering: A, 2015
A-type Ti-29Nb-13Ta-4.6Zr (TNTZ) alloy containing various amounts of TiB reinforcements has been developed to achieve higher fatigue strength for biomedical applications. Fatigue tests were performed at room temperature, and the effects of TiB on fatigue crack initiation and propagation were investigated. The results indicate that the fatigue limit of the TNTZ alloy was substantially improved by the TiB reinforcements. However, the fatigue strength first increased and subsequently decreased as the B concentration increased. TNTZ alloy with 0.10% B has the largest fatigue limit, which is 67% greater than that of the TNTZ alloy. The effects of TiB on the improvement of the fatigue properties are due to the following two factors. First, sliding of the dislocations can be blocked by TiB particles, which results in resistance to 2 fatigue crack initiation. In addition, the crack deflection and crack bridging by the TiB particles could delay the crack propagation. Conversely, debonding of some larger TiB particles may occur, especially when the B concentration is higher than 0.20%. Therefore, the crack initiates from the debonding of the TiB particles and easily propagates along the voids from the interfacial decohesion, which could exert a deleterious influence on the fatigue strength.
Materials Science and Engineering: A, 2014
Thermo-mechanical fatigue (TMF) test of a wrought Co-Cr-Mo alloy was investigated, and Co-based alloy showed superior TMF properties than the control sample of a hot work tool steel. During TMF test, high oxidation resistance and increased hardness were observed in the Co-based alloy in contrast to the low oxidation resistance and decreased hardness in the tool steel. The γ-phase-to-ε-phase transformation of the Co-based alloy was considered as the main hardening factor during the TMF test.
Fatigue Characteristics of Low Cost β Titanium Alloys for Healthcare and Medical Applications
MATERIALS TRANSACTIONS, 2005
Two new low cost titanium alloys, Ti-4.3Fe-7.1Cr (TFC alloy) and Ti-4.3Fe-7.1Cr-3.0Al (TFCA alloy) for healthcare and medical applications have been recently developed. As for such applications, the alloys are necessary to have high fatigue performance. The aim of this study is, therefore, to investigate fatigue characteristics of the alloys subjected to solution treatment above transus. Fatigue tests were carried out at a stress ratio, R, of 0.1 and a frequency of 10 Hz. Fatigue limit of the solution treated TFC alloy is higher than that of the solution treated TFCA alloy, but both are higher than that of the existing biometallic materials. Fatigue strength of the TFC alloy is almost independent of solution treatment temperature, while, fatigue strength of the TFCA alloy strongly depends on solution treatment temperature, especially, in the low cycle fatigue life (LCF) region. The fatigue ratio and biofunctionality of these new alloys are much higher than those of the existing biometallic materials. In general, a crack initiates from the surface in the LCF region and from subsurface (internal) in the high cycle fatigue life (HCF) region for the TFC alloy, while, in the case of the TFCA alloy, a crack tends to initiate from the subsurface in both LCF and HCF regions. The internal crack initiation sites are found to be the area with low phase stability in the LCF region and at the area with high stability of phase in the HCF region. The relatively low fatigue strength of TFCA alloy is associated with the addition of Al that leads to precipitate phase in which both crack initiation and facet formation are easier to occur.
Microstructure and properties of CoCr alloys used in prosthetics procedure
Archives of Materials Science and Engineering
Purpose: The aim of this work was to define the influence of manufacturing technology on the chemical composition, surface topography, physicochemical and electrochemical properties of CoCr alloys obtained by casting technology and Direct Metal Laser Sintering. Design/methodology/approach: This work presents microstructural and chemical compositions obtained by scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDS). Additionally, corrosion pitting analysis and roughness measurement were conducted on the samples. Findings: On the basis of the investigations, it can be stated that the prosthetic restorations are different depending on the type manufacturing technology. Based on the obtained results it was found that the structures of both materials are chemically inhomogeneous. The investigated alloy exhibited similar polarization curve character. Practical implications: The rapid prototyping methods are a new technology used for getting details e.g. by CAD/CAM ...