Carbides and their Role in Advanced Mechanical Properties of L605 Alloy: Implications for Medical Devices

Abstract:

L605 (ASTM F90), a cobalt-chromium-tungsten alloy with excellent mechanical properties and high radiopacity, has been widely accepted as a suitable alloy for stent applications. The presence of carbides in this alloy, primary carbides and secondary carbides, leads to difficulties in controlling mechanical performances and therefore in optimizing stent size and performances. This work is thus to investigate the carbides and their role in advanced mechanical properties of L605 alloy for stent fabrication. Herein, the nature, nucleation, distribution and dissolution of the carbides were investigated in a series of recrystallized L605 tubes from hard-drawn (HD) state. The mechanical properties corresponding to each carbide state were examined by tensile tests and microhardness measurements. The results indicate important relationships among carbide precipitation, grain size and mechanical behaviors, as a function of annealing temperature and duration. The intergranular secondary carbides, induced at the onset of the recrystallization of L605 matrix, were preferentially precipitated at grain boundaries. The nucleation of such particulate phase leads to a pinning effect on grain coarsening, resulting in a strengthening effect of the material. However, the further growth of the secondary carbides brings about considerable reduction of ductility, which is inacceptable for stent application. Therefore, an optimization protocol on carbides controlling was developed to maintain the strengthening effect without losing ductility and small grain size.

• Periodical: Materials Science Forum (Volumes 783-786)
• Pages: 1354-1359
• DOI: https://doi.org/10.4028/www.scientific.net/MSF.783-786.1354
• Online since: May 2014
• Authors: Fan Sun*, Diego Mantovani, Frédéric Prima
• Keywords: Carbide, Cardiovascular Stent, Co-Cr-W-Ni Alloy, Mechanical Property, Thermal Treatment

References

[1] Instruction of HAYNES 25 Alloy, HAYNES International, H-3057D.

[2] G. F. Vander Voort, G. M. Lucas and E. P. Manilova, Metallography and Microstructures of Heat-Resistant Alloys, ASM Handbook. 9 820-859.

DOI: 10.31399/asm.hb.v09.a0003737

[3] P. Poncin, J. Proft, Stent tubing : understanding the desired attributes, Proceedings of the Materials & Processes for Medical Devices Conference, (2003).

[4] P. Poncin, C. Millet, J. Chevy, J. Proft, Comparing and optimizing Co-Cr tubing for stent applications, Proceedings of the Materials & Processes for Medical Devices Conference, (2004).

[5] D. DeAntonio, D. Duhl, T. Howson, M. Rothman, Heat Treating, vol. 4, ASM Handbook, ASM International.

[6] D. Klarstrom, P. Crook and J. Wu, Metallography and Microstrures of Cobalt and Cobalt Alloys, Metallography and Microstructures, Vol 9, ASM Handbook, ASM International.

DOI: 10.31399/asm.hb.v09.a0003771

[7] V. Kuzucu, M. Ceylan, H. Celik, I. Aksoy, Phase investigation of a cobalt base alloy containing Cr, Ni, W and C, Journal of Materials Processing Technology. (1998) 137-141.

DOI: 10.1016/s0924-0136(97)00261-6

[8] W.H. Jiang, H.R. Guan, Z.Q. Hu, Effects of heat treatment on microstructures and mechanical properties of a directionally solidified cobalt-based superalloy, Materials Science & Engineering, A271 (1999) 101-108.

DOI: 10.1016/s0921-5093(99)00183-5

[9] F. Sun, S. Nowak, T. Gloriant, P. Laheurte, A. Eberhardt, F. Prima, Influence of a short thermal treatment on the superelastic properties of a titanium-based alloy. Scripta Materialia 63 (2010) 1053-1056.

DOI: 10.1016/j.scriptamat.2010.07.042

[10] J. Teague, E. Cerreta, M. Stout, Tensile properties and microstructures of Haynes 25 Alloy after aging at elevated temperatures for extended times, Metallurgical and Materials transactions A 35 (2004) 2767-2781.

DOI: 10.1007/s11661-004-0223-4

[11] P. Zieba, G. Cliff, G.W. Lorimer, Discontinuous precipitation in cobalt-tungsten alloys, Acta Materialia. 45 (1997) 2093-(2099).

DOI: 10.1016/s1359-6454(96)00319-9

[12] W.H. Jiang, X.D. Yao, H.R. Guan, Z.Q. Hu, Relatioanship between degeneration of M7C3 and precipitation of M23C6 in a cobalt base superalloy, Materials Science and Technology. 15 (1999) 596-598.

DOI: 10.1179/026708399101506157

[13] W.H. Jiang, X.D. Yao, H.R. Guan, Z.Q. Hu, Secondary carbide precipitation in a directionally solidified cobalt-base superalloy, Metallurgical and Materials transactions A. 30 (1999) 513-552.

DOI: 10.1007/s11661-999-0043-7