Fatigue life determination of plasma nitrided medical grade CoCrMo alloy

Bayrak, Özgü; Yetim, A.F.; Alsaran, Akgün; Çelik, A.

doi:10.1111/j.1460-2695.2010.01442.x

Cited by 10 publications

(1 citation statement)

References 20 publications

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“…Bazzoni et al, (2013) showed that the formation of a 4 to 5 µm thick compound layer (γN at 350 °C and γN+Cr2N at 450 °C) improves the wear resistance and lowers the friction coefficient compared to those of the untreated specimens [19]. Bayak et al, (2010) have reported a decrease in the fatigue limit of the CoCrMo alloy due to nitriding [20]. Literature on the temperature (and hence energy availabe for diffusion), phase formation and changes in the mechanical properties, especially wear resistance after nitriding can be found, however, to the best of our knowledge, an extensive study on the fatigue and fracture toughness behaviour of plasma nitrided CoCrMo alloys that has never been reported.…”

Section: Introductionmentioning

confidence: 99%

Effect of nitriding voltage on the impact load fatigue and fracture toughness behaviour of CoCrMo alloy nitrided utilising a HIPIMS discharge

Shukla

Purandare

Khan

et al. 2020

Surface and Coatings Technology

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CoCrMo alloy specimens were plasma nitrided using a High Power Impulse Magnetron Sputtering (HIPIMS) discharge. In this work the effect of nitriding voltage (-700 V to -1100 V) on the microstructure, surface hardness, impact load fatigue resistance and fracture toughness (KIc) of the alloy has been investigated.Results revealed that the specimens treated at lower nitriding voltages (-700 V and -900 V) develop a nitrided layer consisting a mixture of Co4N+Co2-3N phases. As the nitriding voltage increased (-1000 V and -1100 V), this transformed into a thick layer consisting mainly of Co2-3N with a minor contribution from CrN/Cr2N phases. Accordingly, surface hardness tests after nitriding showed a significant improvement in hardness value (H= 23 GPa) as compared to the untreated specimen, (H= 7.9 GPa). The impact resistance of the alloy also increased with the nitriding voltage. Impact crater profiling of the specimens subjected to impact load tests showed that the depth of the crater decreased significantly, 2 especially at higher nitriding voltages. At the end of the impact load test (one million impacts), the crater depth for an untreated alloy (12.78 μm) was found to be twice to the crater depth measured for the specimen nitrided at -1100 V (7.1 μm). Impact testing results indicate that the fatigue endurance limit of the CoCrMo alloy increased steadily and considerably with the increase of the nitriding voltage. HIPIMS plasma nitriding resulted in a layer material with improved plain strain fracture toughness (KIc), with higher values (KIc) = 1011 MPamm 1/2 (-700 V specimen) were calculated as compared to KIc = 908 MPamm 1/2 for the untreated specimens. Critical material parameter ratios such as H/E (elastic index or elastic strain to failure) and H 3 /E 2 (plastic index) of the nitrided layers were calculated using surface hardness (H) and elastic modulus (E) values obtained with the help of nanoindentation tests. Systematic improvement in the values of H/E and H 3 /E 2 ratios calculated for all nitrided specimens validated the increase in fracture toughness and impact load fatigue resistance of the nitrided specimens as compared to the corresponding properties of the untreated CoCrMo base alloy.

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Section: Introductionmentioning

confidence: 99%

Effect of nitriding voltage on the impact load fatigue and fracture toughness behaviour of CoCrMo alloy nitrided utilising a HIPIMS discharge

Shukla

Purandare

Khan

et al. 2020

Surface and Coatings Technology

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High temperature corrosion and electrochemical behavior of HVOF sprayed Inconel 718 coating using an innovative device: HTCMD

Galedari

Jazi

Azarmi

et al. 2017

Materials & Corrosion

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Inconel 718 is one of the most commonly used nickel‐based superalloy materials in petroleum industry due to its high temperature mechanical properties and corrosion resistance. Generally, corrosion resistance assessment of materials at high temperature condition is a challenging task and most of the previous studies in this area were based on estimation of weight‐loss in the sample, which cannot provide accurate results, and it could be very time‐consuming. In this study, a high temperature corrosion measurement device (HTCMD) was used to evaluate electrochemical behavior of HVOF deposited Inconel 718 coating in 3.5 wt% NaCl solution at elevated temperatures. EIS and potentiodynamic polarization results revealed very low corrosion rate of the Inconel 718 coating. Materials characterization by SEM, XRD, and EDS indicated formation of chromium oxide rich unstable passive layer resulted in localized protection of superalloy material that was not sufficient to provide corrosion protection for the entire surface, during the service at high temperature condition.

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Understanding crack growth within the γ′ Fe4N layer in a nitrided low carbon steel during monotonic and cyclic tensile testing

Varanasi,

Koyama,

Yokoi

et al. 2024

J Mater Sci

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Nitriding is a cost-effective method to realize simultaneous improvements in tensile and fatigue properties and resistance to abrasion and corrosion. Previous studies reported that nitriding pure Fe enhances tensile strength by ~ 70% and fatigue limit by ~ 200%. It is due to the increase in surface hardness caused by the formation of γ′(Fe4N) and ε(Fe2-3N) nitrogen-containing intermetallic compound phases. However, the intermetallic compound layer is prone to brittle-like cracking. To better design nitrided steels, it is crucial to identify the crack growth mechanisms via analysis of the microstructural crack growth paths within the ~ 4–6 µm thick nitride layer. In the current work, we statistically evaluate the crack propagation behavior in the γ′ Fe4N layer during monotonic and cyclic tensile deformation in nitrided low-carbon steel (0.1 wt% C). Since nitriding typically results in the formation of columnar grains, the effect of morphology needs to be clarified. To this end, the steel was shot-peened and subsequently nitrided to promote equiaxed nitride grains morphology (~ 16% increase). Crack growth paths were comparatively evaluated for multiple cracks, and no significant effect of nitride morphology was observed. {100}γ′ is the predominant transgranular crack path in the monotonic tensile tested specimen, followed by {111}γ′. It is despite the elastic modulus of {111}γ′ < {100}γ′. This contrary behavior is explained by {100}γ′ plane having the lowest surface energy (density functional theory calculations). In the cyclic tensile loaded specimen, experiments revealed that transgranular cracking along {100}γ′ (cracking via symmetric dislocation emission) or {111}γ′ (slip plane cracking) is equally likely. Graphical abstract

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Fatigue life determination of plasma nitrided medical grade CoCrMo alloy

Cited by 10 publications

References 20 publications

Effect of nitriding voltage on the impact load fatigue and fracture toughness behaviour of CoCrMo alloy nitrided utilising a HIPIMS discharge

Effect of nitriding voltage on the impact load fatigue and fracture toughness behaviour of CoCrMo alloy nitrided utilising a HIPIMS discharge

High temperature corrosion and electrochemical behavior of HVOF sprayed Inconel 718 coating using an innovative device: HTCMD

Understanding crack growth within the γ′ Fe4N layer in a nitrided low carbon steel during monotonic and cyclic tensile testing

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