Effect of heat-treatment temperature on microstructures and mechanical properties of Co–Cr–Mo alloys fabricated by selective laser melting

Kajima, Yuka; Takaichi, Atsushi; Kittikundecha, Nuttaphon; Nakamoto, Tetsuji; Kimura, Tsuyoshi; Nomura, Naoyuki; Kawasaki, Akira; Hanawa, Takao; Takahashi, Hidekazu; Wakabayashi, Noriyuki

doi:10.1016/j.msea.2018.04.048

Cited by 146 publications

(63 citation statements)

References 52 publications

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“…It was indicated that heat treatment at 800°C for 20 minutes promotes the formation of ε-Co and intermetallic precipitations and/or carbides (Figure 11, [38]). According to Kajima et al [34], heat treatment at 800°C for 6 h can lead to a volume fraction of around 20-25% ε-Co in SLM samples. e formation of the second phases in a sufficient fine distribution (high undercooling) could be the origin of the observed increase in the mechanical values.…”

Section: Heat-treated Conditionmentioning

confidence: 99%

“…is suggests that the metastable c-Co is present in the as-built condition, which is comparable with a recently published study on heat treatments of additively manufactured Co-Cr-Mo. According to Kajima et al [34], ε-Co is only present after an additional heat treatment and the volume fraction between c-Co and ε-Co varies upon the heattreatment temperature, with c-Co remaining as the predominant phase (≥75% volume fraction). e transformation of c-Co to ε-Co is dependent on the grain size, and for finegrained structures (as is the case in SLM), this transformation is suppressed, resulting in the predominant c-Co [35].…”

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confidence: 99%

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Additive Manufacturing of Cobalt‐Based Dental Alloys: Analysis of Microstructure and Physicomechanical Properties

Hitzler

Alifui‐Segbaya

Williams

et al. 2018

Advances in Materials Science and Engineering

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The limitations of investment casting of cobalt-based alloys are claimed to be less problematic with significant improvements in metal additive manufacturing by selective laser melting (SLM). Despite these advantages, the metallic devices are likely to display mechanical anisotropy in relation to build orientations, which could consequently affect their performance “in vivo.” In addition, there is inconclusive evidence concerning the requisite composition and postprocessing steps (e.g., heat treatment to relieve stress) that must be completed prior to using the devices. In the current paper, we evaluate the microstructure of ternary cobalt-chromium-molybdenum (Co-Cr-Mo) and cobalt-chromium-tungsten (Co-Cr-W) alloys built with direct metal printing and LaserCUSING SLM systems, respectively, at 0°, 30°, 60°, and 90° inclinations (Φ) in as-built (AB) and heat-treated (HT) conditions. The study also examines the tensile properties (Young’s modulus, E; yield strength, RP0.2; elongation at failure, At; and ultimate tensile strength, Rm), relative density (RD), and microhardness (HV5) and macrohardness (HV20) as relevant physicomechanical properties of the alloys. Data obtained indicate improved tensile properties and HV values after a short and cost-effective heat-treatment cycle of Co-Cr-Mo alloys; however, the process did not homogenize the microstructure of the alloy. Annealing heat treatment of Co-Cr-W led to significant isotropic characteristics with increased E and At (except for Φ = 90°) in contrast to decreased RP0.2, Rm, and HV values, compared to the AB form. Similarly, the interlaced weld-bead structures in AB Co-Cr-W were removed during heat treatment, which led to a complete recrystallization of the microstructure. Both alloys exhibited defect-free microstructures with RD exceeding 99.5%.

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Section: Heat-treated Conditionmentioning

confidence: 99%

mentioning

confidence: 99%

Additive Manufacturing of Cobalt‐Based Dental Alloys: Analysis of Microstructure and Physicomechanical Properties

Hitzler

Alifui‐Segbaya

Williams

et al. 2018

Advances in Materials Science and Engineering

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“…11, adapted from [38]). According to Kajima et al [34] Figure 12, adapted from [38]. During cooling the observed volume undergoes several post-heating by additive forming of further layers on top of the observed volume, hence, it is possible that a considerable fraction of −Co can be generated via alterations on the process conduct [10].…”

Section: Heat Treated Conditionmentioning

confidence: 99%

Additive Manufacturing of Cobalt-Based Dental Alloys: Analysis of Microstructure and Physico-Mechanical Properties

Hitzler¹,

Alifui‐Segbaya²,

Williams³

et al. 2018

Preprint

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The limitations of investment casting of cobalt-based alloys are claimed to be less problematic with significant improvements in metal additive manufacturing by selective laser melting (SLM). Despite these advantages, the metallic devices are likely to display mechanical anisotropy in relation to build orientations, which could consequently affect their performance ‘in vivo’. In addition, there are inconclusive evidence concerning the requisite composition and post-processing steps (e.g. heat-treatment to relieve stress) that must be completed prior to the devices being used. In the current paper, we evaluate the microstructure of ternary cobalt-chromium-molybdenum (Co-Cr-Mo) and cobalt-chromium-tungsten (Co-Cr-W) alloys built with Direct Metal Printing and LaserCUSING SLM systems respectively at 0°, 30°, 60° and 90° inclinations (Φ) in as-built (AB) and heat-treated (HT) conditions. The study also examines the tensile properties (Young's modulus, E; yield strength, RP0.2; elongation at failure, At and ultimate tensile strength, Rm), relative density (RD), and micro-hardness (HV5) and macro-hardness (HV20) as relevant physico-mechanical properties of the alloys. Data obtained indicate improved tensile properties and HV values after short and cost-effective heat-treatment cycle of Co-Cr-Mo alloy; however, the process did not homogenize the microstructure of the alloy. Annealing heat-treatment of Co-Cr-W led to significant isotropic characteristics with increased E and At (except for Φ = 90º) in contrast to decreased RP0.2, Rm and HV values, compared to the AB form. Similarly, the interlaced weld-bead structures in AB Co-Cr-W were removed during heat-treatment, which led to a complete recrystallization in the microstructure. Both alloys exhibited defect-free microstructures with RD exceeding 99.5%.

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“…SLM is a layer-by-layer process with the same thickness in each layer, so ρ actually represents the molding speed without considering the layering time of each layer. The forming speed is proportional to the laser scanning speed and the lap joint [ 45 ]. E = P / v ·h ·n …”

Section: Resultsmentioning

confidence: 99%

Effect of Selective Laser Melting Process Parameters on Microstructure and Properties of Co-Cr Alloy

et al. 2018

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Due to the rapid melting and solidification mechanisms involved in selective laser melting (SLM), CoCrMo alloys fabricated by SLM differ from the cast form of the same alloy. In this study, the relationship between process parameters and the morphology and macromechanical properties of cobalt-chromium alloy micro-melting pools is discussed. By measuring the width and depth of the molten pool, a theoretical model of the molten pool is established, and the relationship between the laser power, the scanning speed, the scanning line spacing, and the morphology of the molten pool is determined. At the same time, this study discusses the relationship between laser energy and molding rate. Based on the above research, the optimal process for the laser melting of cobalt-chromium alloy in the selected area is obtained. These results will contribute to the development of biomedical CoCr alloys manufactured by SLM.

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Effect of heat-treatment temperature on microstructures and mechanical properties of Co–Cr–Mo alloys fabricated by selective laser melting

Cited by 146 publications

References 52 publications

Additive Manufacturing of Cobalt‐Based Dental Alloys: Analysis of Microstructure and Physicomechanical Properties

Additive Manufacturing of Cobalt‐Based Dental Alloys: Analysis of Microstructure and Physicomechanical Properties

Additive Manufacturing of Cobalt-Based Dental Alloys: Analysis of Microstructure and Physico-Mechanical Properties

Effect of Selective Laser Melting Process Parameters on Microstructure and Properties of Co-Cr Alloy

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