Corrosion behaviour assessment of cast and HIPed Stellite 6 alloy in a chloride-containing environment

Rosalbino, Francesco; Scavino, Giorgio

doi:10.1016/j.electacta.2013.08.019

Cited by 41 publications

(28 citation statements)

References 24 publications

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“…Nevertheless, there still exists some controversy over the type of oxide that can be formed, the mechanism of oxide formation and growth, and the effect of the oxide film on corrosion kinetics of these alloys. This may have arisen due to the role of the different aqueous redox environments and mass transport conditions in those studies [13][14][15][16][17][18][19][20][21]. The challenge in fully understanding corrosion kinetics is linked to understanding the roles that elements of the solution environment (pH, temperature, ionic strength and the chemical and redox activities of aqueous species) play in the corrosion process for a given alloy.…”

Section: Introductionmentioning

confidence: 99%

Potentiostatic Oxide Growth Kinetics on Ni-Cr and Co-Cr Alloys: Potential and pH Dependences

Musa

Behazin

Wren

2015

Electrochimica Acta

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Section: Introductionmentioning

confidence: 99%

Potentiostatic Oxide Growth Kinetics on Ni-Cr and Co-Cr Alloys: Potential and pH Dependences

Musa

Behazin

Wren

2015

Electrochimica Acta

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“…Hem oda sıcaklığında hem de yüksek sıcaklıklarda üstün korozyon ve oksidasyon direnci ile mekanik ve tribolojik özelliklerin eşsiz bir kombinasyonunu sergileyen Stellite alaşımları [7] Co esaslı süper alaşımların önde gelenlerindendir [8]. Co esaslı süperalaşımların uygulamaları geleneksel olarak en çok nükleer endüstriye yönelik iken [9] günümüzde Stellite alaşımlarının kullanımı odun hamuru, kağıt işleme, petrol ve gaz işleme, ilaç sanayi ve kimyasal işleme gibi farklı endüstriyel alanlara yayılmıştır [10]. Bu denli yaygın kullanım alanına sahip Stellite alaşımlarının en önde gelenlerinden biri kuşkusuz 1900'lü yılların başında Elwood Haynes tarafından geliştirilmiş ilk Stellite alaşımı olan Stellite 6'dır [11,12].…”

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“…[24]. Stellite alaşımları üzerine yapılan çok sayıda çalışmada ise tam yoğunluğa ulaşılabilmesi için sıcak izostatik presleme (HIP) yöntemi kullanılmıştır [1,10,22,29,30]. Bazı çalışmalarda HIP ile üretilen malzemelere ikinci bir HIP'leme işlemi uygulanmıştır [22].…”

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Toz metalurjisi tekniği ile üretilen kobalt esaslı süperalaşımlarda element ilavelerinin mikroyapı ve mekanik özelliklere etkisi

Özgün¹,

Akbulut²

2017

SAÜ Fen Bilimleri Enstitüsü Dergisi

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ÖZBu çalışmada, toz metalurjisi (T/M) tekniği ile element tozlarından üretilen Stellite 6 süperalaşım malzemelerin mikroyapı ve mekanik özelliklerine Fe ve B elementlerinin etkisi incelenmiştir. Yüksek saflıktaki element tozlarından farklı oranlarda Fe ve B içeriğine sahip karışım tozlar hazırlanmıştır. Hazırlanan karışımlar T/M yöntemi ile şekillendirilip farklı sıcaklıklarda sinterlenmişlerdir. Sinterleme işlemlerinin başarısı yoğunluk ölçümleri ile değerlendirilmiştir. Mikroyapısal karakterizasyon X-ışınları analizi (XRD), taramalı elektron mikroskobu (SEM) incelemeleri ve enerji dağılımı spektrometresi (EDS) ile gerçekleştirilmiştir. Mekanik özelliklerin karakterizasyonu için mikrosertlik ölçümleri yapılmıştır. Stellite 6 numunelerinin mikroyapısında, kullanılan Cr tozunun iri boyutlu olması nedeniyle iri boyutlu karbürlerin oluştuğu tespit edilmiştir. B ilavesi ile birlikte bağıl yoğunluk değerleri bir miktar artmıştır. B ile birlikte Fe elementinin ilave edilmesiyle bağıl yoğunluk önemli ölçüde artış göstermiştir.Anahtar Kelimeler: Stellite 6, B ilavesi, Fe ilavesi, yoğunluk, mikroyapı, sertlikThe effect of element additions on the microstructure and the mechanical properties of cobalt based superalloys produced via powder metallurgy technique ABSTRACT In this study, the effect of Fe and B elements on the microstructure and mechanical properties of Stellite 6 superalloy materials produced from elemental powders by powder metallurgy (P/M) technique was investigated. Powder mixtures contained different Fe and B content were prepared from high purity elemental powders. The prepared powder mixtures were shaped by P/M method and then sintered at various temperatures. The success of sintering operations was determined by density measurements. Microstructural characterization was carried out with X-ray diffraction analysis (XRD), scanning electron microscope (SEM) and energy dispersive spectrometry (EDS). Microhardness measurements were conducted for to characterize mechanical properties. Due to large particle size of the used Cr powder coarse carbides formed in the microstructure of Stellite 6 samples. Relative density values increased slightly with B addition. Relative density was increased dramatically by the addition of Fe element with B.

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“…This is because the carbides in HIPed Stellite 6 are uniformly distributed around the Co solid solution matrix in spheroidal form rather than the dendritic carbides in as-cast Stellite 6, as shown in Figure 2 The different times of exposure also showed a difference in the EIS results between the two alloys from different processes. Higher Rct values of the HIPed Stellite 6 are compared to that of the ascast Stellite 6, as shown in Table 2-4 for longer exposure times, which are an indication that prolonged exposure to the corrosive solution had improved the protective property of the oxide layer displaying higher stability [18]. Furthermore, looking at the hysteresis loop, as shown in Figure 2 Solution [10].…”

Section: Previous Researchmentioning

confidence: 87%

“…Previous research done on different types of Stellite alloys investigate general and localized corrosion behaviour as well as oxide integrity primarily in salt and acidic mediums. Rosalbino and Scavino investigated the corrosion behaviour of as-cast Stellite 6 and hot isostatic pressing (HIP) processed Stellite 6 in 3.5 wt.% NaCl solution using EIS and potentiodynamic polarization methods [18]. The experimental results showed that the HIPed Stellite 6 had much better corrosion performance compared to as-cast Stellite 6.…”

Section: Previous Researchmentioning

confidence: 99%

Corrosion Behaviour of High-Carbon High-Molybdenum Stellite Alloys in Amine Environment

Kamal¹

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Stellite alloys are cobalt-based alloys which display exceptional mechanical properties, wear and corrosion resistance owing to its unique chemical compositions. Stellite 6 is the most popular Stellite alloy employed in various applications, one of which is the hardfacing of valve trim components within control valves in boiler feedwater treatment systems where hydrazine and/or amine derivatives are used. Erosion-corrosion caused failure of Stellite 6 hardfacing has been reported from industry in such applications. To find a better replacement of Stellite 6 for improved corrosion resistance in amine environment, 700 series Stellite alloys, including Stellite 706, Stellite 712 and Stellite 720, are proposed, which are high-carbon high-molybdenum Stellite alloys. The corrosion performance of these alloys in morpholine solution with pH 9.5, which simulates the corrosive environment of boiler feedwater service, is evaluated using a series of electrochemical tests such as electrochemical impedance spectroscopy (EIS), potentiodynamic polarization and potentiostatic polarization. Both regular polarization tests (potential up to 1.2 V) and failure polarization tests (potential up to 12 V) are conducted on the alloys. The former identifies generaland localized corrosion behaviour, while the latter intends to fail the alloy surface to analyze their limitations. Two different surface conditions (intact and damaged) and two different temperature variables (25°C and 50°C) are also studied to simulate erosion-corrosion behaviour. Stellite 6 alloy is also tested under the same condition for comparison. It is shown that these 700 series Stellite alloys are comparably better than Stellite 6 with respect to oxide film stability, all exhibiting excellent corrosion resistance in morpholine solution with pH 9.5. The protective chromium oxide film on their surfaces is retained well for both regular and failure tests. These alloys behave similarly, however, Stellite 720 containing the highest carbon and molybdenum contents performed better at room temperature and Stellite 706 with the least carbon and molybdenum iii contents performed better at the elevated temperature. Although wear changes the surface condition, the corrosion resistance of the worn alloys is similar to that of intact alloys in the tested solution. The outcomes of this research suggest that 700 series Stellite alloys are good candidates for replacing Stellite 6, where Stellite 720 displayed the best performance under the conditions tested.iv

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Corrosion behaviour assessment of cast and HIPed Stellite 6 alloy in a chloride-containing environment

Cited by 41 publications

References 24 publications

Potentiostatic Oxide Growth Kinetics on Ni-Cr and Co-Cr Alloys: Potential and pH Dependences

Potentiostatic Oxide Growth Kinetics on Ni-Cr and Co-Cr Alloys: Potential and pH Dependences

Toz metalurjisi tekniği ile üretilen kobalt esaslı süperalaşımlarda element ilavelerinin mikroyapı ve mekanik özelliklere etkisi

Corrosion Behaviour of High-Carbon High-Molybdenum Stellite Alloys in Amine Environment

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