Investigation of the Effect of Atmosphere and Carbon Content on Microstructure and Mechanical Properties of Co-Cr-Mo Superalloy Dental Blocks Produced by Centrifugal Casting Method

Öz

In this study, the effect of casting parameters on microstructure and mechanical properties of Co-Cr-Mo superalloy dental blocks produced by centrifugal investment casting method was investigated. In addition, the effects of atmosphere environment and carbon content were investigated during casting processes. After the casting process, metallographic examination, SEM, XRD, EDS, tensile test and hardness test were performed in order to determine the microstructures and mechanical properties. As a result of the microstructure tests, while it was observed that Cr23C6 carbides were formed in all of the low-carbon blocks produced in open and vacuum environment, Cr7C3 carbide type was formed in high-carbon blocks in open atmosphere environment, and Co3C carbide in lamellar structure was formed in addition to Cr7C3 carbide in high-carbon blocks in vacuum environment. High carbon alloy blocks have a higher carbide volume ratio than low carbon alloy blocks. High tensile strength and the highest total elongation value were obtained in the low carbon alloy blocks with centrifuge speed of 225 rpm in vacuum environment. Hardness value is higher in high carbon alloy than low carbon alloy. While smooth surface splitting fracture was observed in the parts cast with high carbon alloy, pitting fracture surface was observed in low carbon alloy.

Anahtar Kelimeler

• Co-Cr-Mo Alloy
• Centrifugal ınvestment casting
• vacuum environment
• superalloys
• metallic biomaterials

Santrifüj Hassas Döküm Yöntemiyle Üretilen Co-Cr-Mo Süperalaşım Dental Blokların Mikroyapı ve Mekanik Özellikleri Üzerine Atmosfer ve Karbon Miktarının Etkisi

Öz

Bu çalışmada, santrifüj hassas döküm yöntemiyle üretilen Co-Cr-Mo süperalaşım dental bloklarda döküm parametrelerinin mikroyapı ve mekanik özellikler üzerine etkisi araştırılmıştır. Ayrıca döküm işlemleri esnasında atmosfer ortamı ve karbon miktarının etkileri incelenmiştir. Döküm işlemi sonrasında mikroyapı ve mekanik özellikleri belirlenmesi amacıyla metalografik inceleme, SEM, XRD, EDS, çekme ve sertlik testleri yapılmıştır. Mikroyapı incelemeleri sonucunda, açık ve vakum atmosferde üretilen düşük karbonlu blokların tamamında Cr23C6 karbürleri gözlenirken, yüksek karbonlu bloklarda açık atmosfer ortamında Cr7C3 karbür tipi, yüksek karbonlu bloklarda vakum ortamında Cr7C3 karbüre ek olarak lamelli yapıda Co3C karbürü oluştuğu gözlemlenmiştir. Yüksek karbonlu alaşım ile üretilen bloklarda, düşük karbonlu alaşım ile üretilen bloklara göre yüzde karbür hacim oranı daha yüksek olduğu belirlenmiştir. Düşük karbonlu alaşımda vakum ortamında 225 devir/dakika santrifüj hızı ile üretilen blokta yüksek çekme mukavemeti ve en yüksek toplam uzama değeri elde edilmiştir. Sertlik değeri yüksek karbonlu alaşımda düşük karbonlu alaşıma göre daha yüksek olduğu belirlenmiştir. Yüksek karbonlu alaşım ile dökülen parçalarda düzgün yüzey ayrılma kırılması gözlemlenirken, düşük karbonlu alaşımda çukurcuklu kırılma yüzeyi gözlenmiştir.

Anahtar Kelimeler

• Santrifüj hassas döküm
• vakum ortamı
• süperalaşımlar
• metalik biyomalzemeler
• cr-cr-mo alaşım

Kaynakça

1. [1] Taşcıoğlu, S., & Akar, N., “A novel alternative to the additives in investment casting pattern wax compositions”, Materials & Design, 24(8), 693-698, (2003).
2. [2] Taşcıoğlu, S., & Akar, N., “Conversion of an investment casting sprue wax to a pattern wax by chemical agents”, Materials and Manufacturing Processes, 18(5), 753-768, (2003).
3. [3] Taşcıoğlu, S., Inem, B., & Akar, N., “Conversion of an investment casting sprue wax to a pattern wax by the modification of its properties. Materials & Design, 25(6), 499-505, (2004).
4. [4] Fleming T.J., Kavanagh A., Duggan G., O’Mahony B., Higgens M., “The effect of induction heating power on the microstructural and physical properties of investment cast ASTM-F75 CoCrMo alloy”, Journal of Materials Research and Technology, 8(5): 4417-4424, (2019).
5. [5] Yıldırım M., Keleş A., “Production of Co-Cr-Mo Biomedical Alloys via Investment Casting Technique”, Turkish Journal of Electromechanics and Energy, 3(1): 12-16, (2018).
6. [6] Cuao-Moreu C.A., Hernández-Sanchéz E., Alvarez-Vera M., Garcia-Sanchez E.O., Perez-Unzueta A., Hernandez-Rodriguez M.A.L. “Tribological behavior of borided surface on CoCrMo cast alloy”. Wear, 426: 204-211, (2019).
7. [7] Zhang E., Liu C., “A new antibacterial Co-Cr-Mo-Cu alloy: preparation, biocorrosion, mechanical and antibacterial property”, Materials Science and Engineering C, 69: 134-143, (2016).
8. [8] Yamanaka K., Mori M., Chiba A. “Effects of Nitrogen Addition on Microstructure and Mechenical Behavior of Biomedical Co-Cr-Mo Alloys”, Journal of the Mechenical Behavior of Biomedical Materials, 29: 417-426. (2014).

9. [9] Park J.B., Jung K.H., Kim K.M., Son Y., Lee J.I., Ryu J.H., “Microstructure of as-cast Co-Cr-Mo alloy prepared by investment casting”, Journal of the Korean Physical Society, 72(8): 947-951, (2018).
10. [10] Yamanaka K., Mori M., Kuramoto K, Chiba A., “Development of New Co-Cr-W- based Biomedical Alloys: Effects of Microalloying and Thermomechanical Processing on Microstructures and Mechanical Properties”, Materials & Design, 55: 987-998. (2014).
11. [11] Giacchi J.V., Morando C.N., Fornaro O., Palacio H.A., “Microstructural Characterizationof As-Cast Biocompatible Co-Cr-Mo Alloys”, Materials Characterization, 62: 53-61, (2013).
12. [12] Kaiser R., Williamson K., O’Brien C., Ramirez-Garcia S., Browne D.J., “The İnfluence of Cooling Conditions on Grain Size, Secondary Phase Precipitates and Mechanical Properties of Biomedical Alloy Specimens Produced by İnvestment Casting”, Journal of the Mechenical Behavior of Biomedical Materials, 24: 53-63, (2013).
13. [13] ASTM F75 CoCr Alloy, Arcam EBM System
14. [14] ASTM F-75, “Standard Specification for Cobalt-28Chromium-6 Molybdenum Alloy Castings and Casting Alloy for Surgical Implants”, (2012).
15. [15] Alfırano, Agustini, P., & Iwan, S., "Microstructural and Mechanical Characterization of As-Cast Co-Cr-Mo Alloys with Various Content of Carbon and Nitrogen." Materials Science Forum, 988: 206-211, (2020).
16. [16] Mori M., Yamnaka K., Matsumoto H., Chiba A., “Evolution of Cold-Rolled Microstructres of Biomedical Co-Cr-Mo alloys with and without N Doping”, Materials Science and Engineering A 528: 614-621, (2010).
17. [17] ASTM E-8/8M, “Standard Test Methods for Tension Testing of Metallic Material”,ASM International, Metals Park, OH, USA, (2015).
18. [18] Kaiser R., Williamson K., O’Brien C., Browne D J., “Effects of Section Size, Surface Cooling Conditions, and Crucible Material on Microstructure and As-Cast Properties of Investment Cast Co-Cr Biomedical Alloy”, Metallugical and Materials Transactions, 44A: 5333-5341, (2013).
19. [19] Narushima T., Mineta S., Kurihara Y. and Ueda K., “Precipitates in Biomedical Co-Cr Alloys”, JOM, 65: 489-504, (2013).
20. [20] Ramirez-Vidaurri L.E., Castro-Roman M., Herrera-Trejo M., Garcia-Lopez C.V., Almanza-Casas E., “Cooling Rate and Carbon Content Effect On The Fraction of Secondary Phases Precipitate in As-Cast Microstructure of ASTM F-75”, Journal of Materials Processing Technology 209: 1681-1687, (2008).
21. [21] ASM Metals Handbook, Casting, Vol. 2, ASM International, Metals Park, OH, USA., (1990).