Martensitic Transformation in a Cast Co-Cr-Mo-C Alloy

López, H. F.; Saldívar-García, Armando J.

doi:10.1007/s11661-007-9370-8

Cited by 113 publications

(63 citation statements)

References 32 publications

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“…HIP'd specimens exhibited consistently lower impact toughness than forged specimens over a wide range of temperatures; temperatures at which a plasticity-induced transformation of ductile austenite to brittle martensite can occur. The austenite (c) to martensite (a¢) transition is a well-known diffusionless phase transformation, [11][12][13][14] in which the atoms within the c face centered cubic (FCC) matrix are realigned as new crystal lattices. This realignment not only results in a different orientation but also produces a different crystal structure, termed martensite, and can have either a body centered tetragonal (BCT) phase or a body centered cubic (BCC) phase depending on the carbon content of the steel.…”

Section: Introductionmentioning

confidence: 99%

A Microstructural Study on the Observed Differences in Charpy Impact Behavior Between Hot Isostatically Pressed and Forged 304L and 316L Austenitic Stainless Steel

Cooper

Bell

et al. 2015

Metall Mater Trans A

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With near-net shape technology becoming a more desirable route toward component manufacture due to its ability to reduce machining time and associated costs, it is important to demonstrate that components fabricated via Hot Isostatic Pressing (HIP) are able to perform to similar standards as those set by equivalent forged materials. This paper describes the results of a series of Charpy tests from HIP'd and forged 304L and 316L austenitic stainless steel, and assesses the differences in toughness values observed. The pre-test and post-test microstructures were examined to develop an understanding of the underlying reasons for the differences observed. The as-received microstructure of HIP'd material was found to contain micro-pores, which was not observed in the forged material. In tested specimens, martensite was detectable within close proximity to the fracture surface of Charpy specimens tested at 77 K (À196°C), and not detected in locations remote from the fracture surface, nor was martensite observed in specimens tested at ambient temperatures. The results suggest that the observed changes in the Charpy toughness are most likely to arise due to differences in as-received microstructures of HIP'd vs forged stainless steel.

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Section: Introductionmentioning

confidence: 99%

A Microstructural Study on the Observed Differences in Charpy Impact Behavior Between Hot Isostatically Pressed and Forged 304L and 316L Austenitic Stainless Steel

Cooper

Bell

et al. 2015

Metall Mater Trans A

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“…It is now well known that the tensile properties and hardness of Co-Cr-Mo alloys with high carbon content (0.15 to 0.35 mass pct) can be improved significantly by aging treatment at temperatures between 923 K and 1173 K (650°C and 900°C), since a lamellar structure with a high M 23 C 6 carbide content can be obtained. [5][6][7][8][9] However, it has been reported that these carbides increase the rate of polyethylene wear debris in metal-on-polyethylene (MOP) joint replacements, which leads to osteolysis and in some cases to loosening of the components. [10] In order to solve this problem, metalon-metal (MOM) compositions employing Co-Cr-Mo alloys are often used for hip and knee joint replacements instead of MOP.…”

Section: Introductionmentioning

confidence: 99%

“…The ductility of the alloy increases with increasing c phase volume fraction [9,[15][16][17] due to an independent slip system, according to von Mises criteria. Nitrogen addition to the alloy is effective for stabilization of the c phase, even at room temperature.…”

Section: Introductionmentioning

confidence: 99%

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Isothermal Phase Transformation in Biomedical Co-29Cr-6Mo Alloy without Addition of Carbon or Nitrogen

Kurosu

Matsumoto

Chiba

2010

Metall Mater Trans A

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SHINGO KUROSU, HIROAKI MATSUMOTO, and AKIHIKO CHIBAThe isothermal phase transformation behavior in a biomedical Co-29Cr-6Mo alloy without carbon or nitrogen was investigated during aging at temperatures between 973 K and 1273 K (700°C and 1000°C) for up to 90 ks. Transformation from the c to the e phase did not occur at 1273 K (1000°C) as the c phase was more stable than the e phase, and the r phase precipitated at the c grain boundaries. At 1173 K (900°C), a c fi e 1 phase transformation occurred by massive precipitation. Prolonged annealing at 1173 K (900°C) led to a lamellar structure of e 2 and r phases at e 1 /e 1 boundaries by a discontinuous/cellular reaction, expressed by the reaction equation e 1 fi e 2 + r. After decreasing the aging temperature to 973 K (700°C), transformation from the c to the e phase occurred mainly by isothermal martensitic transformation, but a lathlike massive e 1 phase and e 2 /r lamellar colonies were also observed at the original c-grain boundaries. It is likely that not adding carbon results in the promotion of the massive transformation and the precipitation of the r phase during isothermal aging in the Co-29Cr-6Mo alloy system, whose composition corresponds to the ASTM F75 standard for metallic materials for surgical implantation. The resultant isothermal transformation behavior of the present alloy is described on the basis of thermodynamic calculations using Thermo-Calc.

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“…[21] This phase transformation is difficult to accomplish. The martensitic transformation of Co occurs due to cooling from a critical temperature.…”

Section: Phasesmentioning

confidence: 99%

Mechanism of Chromium Oxide Formation in Cobalt–Chromium–Molybdenum (F75) Alloys Prepared Using Spark Plasma Sintering

et al. 2011

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Metallic implants are known to have higher wear rates compared to ceramic. This causes more wear debris to be produced and results in the release of toxic metal ions to the surrounding areas. The strengthening mechanism in cobalt based cast orthopedic alloys depends upon carbides present in the microstructure, but these cause problems when dislodged between articulating surfaces, accelerating wear by abrasion and fretting. Thus, in order to improve the performance of these implants a novel method of processing the alloys, namely by spark plasma sintering (SPS) of fine powders, has been used as it generates hard oxides and not carbides in the microstructure. The oxide in the SPS processed alloy is identified as chromium oxide formed by a redox reaction between cobalt oxide found on the surface of cobalt particles and chromium. The oxygen associated with the cobalt powder is displaced and combines with the chromium during SPS. This oxide in the microstructure of the alloy can be more beneficial than carbides due to its higher hardness, resulting in lower wear rates and less wear particles. With the oxide in the microstructure, the hardness of the alloy becomes closer to that of ceramics. Also its lower density enables the alloy to be lighter. The chemical stability of the oxide ensures that it remains intact and due its insolubility in water, no carcinogenic or toxic reactions will occur.

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Martensitic Transformation in a Cast Co-Cr-Mo-C Alloy

Cited by 113 publications

References 32 publications

A Microstructural Study on the Observed Differences in Charpy Impact Behavior Between Hot Isostatically Pressed and Forged 304L and 316L Austenitic Stainless Steel

A Microstructural Study on the Observed Differences in Charpy Impact Behavior Between Hot Isostatically Pressed and Forged 304L and 316L Austenitic Stainless Steel

Isothermal Phase Transformation in Biomedical Co-29Cr-6Mo Alloy without Addition of Carbon or Nitrogen

Mechanism of Chromium Oxide Formation in Cobalt–Chromium–Molybdenum (F75) Alloys Prepared Using Spark Plasma Sintering

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