Investigation of Different Carbon Ratio and Temperature Effects on Impact Toughness Properties of Nickel Added Powder Metallurgy Steels

Abstract

In this study, impact toughness properties were investigated by adding nickel element to Powder Metallurgy (PM) steels with different carbon ratios. For this purpose, 0.4% - 0.8 - 1.2% by weight natural graphite, 2% nickel and 0.5% zinc stearate as lubricant were added to the pure iron powder, respectively. Impact test samples were produced by shaping the prepared powder mixtures at room temperature and 700 MPa pressing pressure in a single-acting mold. Then, it was sintered at 1200 ºC in a vacuum atmosphere of 5x10-2 Pa for 20 minutes. After the sintering process, impact toughness values were determined by applying the impact test to powder metal steels at different temperatures. Depending on the chemical composition of the alloy, SEM microstructure and fracture surface analyzes were performed and the relationships between macrohardness values and impact toughness were investigated. It has been determined that nickel-rich ferritic solid solution forms in the microstructure of nickel-added PM steels and suppresses the precipitation of pearlite. All samples had very low impact toughness at -20 °C, while the impact test values at +40 °C decreased with increasing carbon content.

Keywords

• Powder metallurgy
• impact toughness
• fracture surface
• nickel addition steel

Nikel İlaveli Toz Metalurjisi Çeliklerin Darbe Tokluk Özelliklerine Farklı Karbon Oranı ve Sıcaklık Etkilerinin İncelenmesi

Abstract

Bu çalışmada farklı karbon oranlarına sahip Toz Metalurjisi (TM) çeliklere nikel elementi ilave edilerek darbe tokluk özellikleri incelenmiştir. Bu amaçla saf demir tozuna sırasıyla ağırlıkça % 0,4 - 0,8 - 1,2 oranlarında doğal grafit , % 2 oranında nikel ve yağlayıcı olarak ise % 0,5 çinko stearat ilave edilmiştir. Hazırlanan toz karışımları, oda sıcaklığında ve tek etkili kalıpta 700 MPa presleme basıncında şekillendirilerek darbe test numuneleri üretilmiştir. Ardından 1200 ºC sıcaklıkta 5x10-2 Pa vakum ortamında 20 dk süre sinterlenmiştir. Sinterlenme işlemi sonrasında toz metal çeliklere farklı sıcaklıklarda darbe testi uygulanarak darbe tokluk değerleri belirlenmiştir. Alaşımın kimyasal bileşimine bağlı olarak SEM mikroyapı ve kırık yüzey analizleri yapılarak, makrosertlik değerleri ile darbe toklukları arasındaki ilişkiler incelenmiştir. Nikel ilaveli TM çeliklerin mikroyapılarında nikelce zengin ferritik katı çözeltinin oluşarak perlit çökelmesini baskıladığı belirlenmiştir. -20 °C’de tüm numuneler çok düşük darbe tokluğuna sahipken, +40 °C’de yapılan darbe testi değerleri artan karbon oranıyla azalmıştır.

Keywords

• Toz metalurjisi
• darbe tokluğu
• kırık yüzey
• nikel ilaveli çelik

References

1. [1] Barani, A. A., Li, F., Romano, P., Ponge, D., & Raabe, D., “Design of high-strength steels by microalloying and thermomechanical treatment”, Materials Science and Engineering: A, 463(1-2), 138-146, (2007).
2. [2] Zhong, N., Wang, X. D., Wang, L., & Rong, Y. H. “Enhancement of the mechanical properties of a Nb-microalloyed advanced high-strength steel treated by quenching–partitioning–tempering process”, Materials Science and Engineering: A, 506(1-2), 111-116, (2009).
3. [3] Delincé, M., Bréchet, Y., Embury, J. D., Geers, M. G. D., Jacques, P. J., & Pardoen, T., “Structure–property optimization of ultrafine-grained dual-phase steels using a microstructure-based strain hardening model”, Acta Materialia, 55(7), 2337-2350, (2007).
4. [4] Güral, A., & Altuntaş, O., “Improving the impact toughness properties of high carbon powder metallurgy steels with novel spherical cementite in the bainitic matrix (SCBM) microstructures”, Materials Chemistry and Physics, 259, 124203, (2021).
5. [5] Nishijima, S., Ishii, A., Kanazawa, K., Matsuoka, S., & Masuda, C.,“NRIM fatigue data sheet technical document”, No. 5. National Research Institute for Metals, Tokyo, 37, (1989).
6. [6] Bouaziz, O., Zurob, H., & Huang, M., “Driving force and logic of development of advanced high strength steels for automotive applications”, Steel Research International, 84(10), 937-947, (2013).
7. [7] Skoglund, P., Litstrom, O., & Flodin, A., “Improvement of Powder Metallurgy Gears for Engines and Transmissions”, SAE Technical Paper, (No. 2013-32-9102), (2013).
8. [8] Ramakrishnan, P. "Automotive applications of powder metallurgy." Advances in powder metallurgy. Woodhead Publishing, 493-519,(2013).

9. [9] Altuntaş, O., & Güral, A.,“Designing spherical cementite in bainitic matrix (SCBM) microstructures in high carbon powder metal steels to improve dry sliding wear resistance”, Materials Letters, 249, 185-188, (2019).
10. [10] A Güral, A., Tekeli, S., & Gürü, M., “Effect of different heat treatments on microstructure of Ni added steels produced by P/M method”, European Powder Metallurgy Congress and Exhibition, Prague, 175-180, (2005).
11. [11] Shanmugasundaram, D. A. C. R., & Chandramouli, R. “Tensile and impact behaviour of sinter-forged Cr, Ni and Mo alloyed powder metallurgy steels”, Materials & Design, 30(9), 3444-3449, (2009).
12. [12] Tracey, V., “Nickel sintered steels—Developments, status and prospects”, Metal Powder Report, 47(11), 49, (1992).
13. [13] Ahssi, M. A. M., Erden, M. A., Acarer, M., & Çuğ, H. “The Effect of Nickel on the Microstructure, Mechanical Properties and Corrosion Properties of Niobium–Vanadium Microalloyed Powder Metallurgy Steels”, Materials, 13(18), 4021, (2020).
14. [14] Tekeli, S., & Güral, A,. “Effect of intercritical annealing and quenching plus tempering heat treatments on microstructure of Ni added powder metallurgy steels”, Materials & Design, 28(4), 1353-1357, (2007).
15. [15] Narasimhan, K. S., & Semel, F. J,. “Sintering of powder premixes-a brief overview”, Advances in Powder Metallurgy and Particulate Materials, 1(05), (2007).
16. [16] Sarıtaş, S., Türker, M., & Durlu, N. “Toz metalurjisi ve parçacıklı malzeme işlemleri”, Türk Toz Metalurjisi Yayınları, 5, 2-34, (2007).
17. [17] Ozer, A.,“The microstructures and mechanical properties of Al-15Si-2.5 Cu-0.5 Mg/(wt%) B4C composites produced through hot pressing technique and subjected to hot extrusion, Materials Chemistry and Physics, 183, 288-296. (2016).
18. [18] Aksöz, S., & Bostan, B., “Effects of ageing and cryo-ageing treatments on microstructure and hardness properties of AA2014–SiC MMCs” Transactions of the Indian Institute of Metals, 71(8), 2035-2042, (2018).