The present work investigates the influence of Ni content on the microstructure evolution of Al0.5CoCrFeNix high‐entropy alloys followed by the study on their corrosion behavior in acid and alkaline solutions, respectively. The microscopic characterization demonstrates that the transformation from a BCC single‐phase to a triple‐phase (BCC + FCC + B2) structure occurs with the increase of Ni content. The corrosion behavior of Al0.5CoCrFeNix high‐entropy alloys was evaluated by electrochemical measurements coupled with morphology analysis. It is found that the corrosion on Al0.5CoCrFeNi0 high‐entropy alloy in both acid and alkaline media is uniform due to its homogeneous microstructure. In contrast, the increase of Ni content leads to the formation of Al, Ni enriched B2 phase with lower Volta potential, causing the respective occurrence of selective dissolution in acid and preferential oxidation in alkaline on the Al0.5CoCrFeNi0.2, Al0.5CoCrFeNi0.6, and Al0.5CoCrFeNi0.8 high‐entropy alloys.
{"title":"Effects of Ni content on the corrosion behavior of Al0.5CoCrFeNix high entropy alloys in acid and alkaline media","authors":"Qi Dong, Wenchao Jia, Zequn Zhang, Dingxin Zhang, Junsheng Wu, Bowei Zhang","doi":"10.1002/maco.202112851","DOIUrl":"https://doi.org/10.1002/maco.202112851","url":null,"abstract":"The present work investigates the influence of Ni content on the microstructure evolution of Al0.5CoCrFeNix high‐entropy alloys followed by the study on their corrosion behavior in acid and alkaline solutions, respectively. The microscopic characterization demonstrates that the transformation from a BCC single‐phase to a triple‐phase (BCC + FCC + B2) structure occurs with the increase of Ni content. The corrosion behavior of Al0.5CoCrFeNix high‐entropy alloys was evaluated by electrochemical measurements coupled with morphology analysis. It is found that the corrosion on Al0.5CoCrFeNi0 high‐entropy alloy in both acid and alkaline media is uniform due to its homogeneous microstructure. In contrast, the increase of Ni content leads to the formation of Al, Ni enriched B2 phase with lower Volta potential, causing the respective occurrence of selective dissolution in acid and preferential oxidation in alkaline on the Al0.5CoCrFeNi0.2, Al0.5CoCrFeNi0.6, and Al0.5CoCrFeNi0.8 high‐entropy alloys.","PeriodicalId":18223,"journal":{"name":"Materials and Corrosion","volume":"1 1","pages":"1274 - 1285"},"PeriodicalIF":0.0,"publicationDate":"2022-03-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77594978","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Thin coatings AlN, AlZrN, and AlCrN were deposited by pulsed magnetron sputtering. The high‐speed steel Т1, structural alloy steel 5140, and structural carbon steel 1017 were used as substrates. The magnetron current, nitrogen content in the gas mixture, and bias voltage on the substrate were changed to obtain nanostructured and amorphous layers of coatings with different elemental compositions. The voltammetry and impedance spectroscopy were performed on the coated samples in 3% NaCl solution. The corrosion behavior of the coatings was characterized by the corrosion current density icorr, the polarization resistance Rp (at the corrosion potential), the ratios icorr,s/icorr, and Rp/Rp,s, where subscript s refers to the substrate. It was shown that the coatings under study (except AlN) are electrochemically active, and the corrosion processes occur not only on the substrate in the coating discontinuity but on the coating surface as well. The coatings AlN/T1, AlZrN/5140, AlCrN/T1, and AlCrN/5140 with icorr ~ 10−7 A cm−2 are found to be the most corrosion‐resistant in 3% NaCl. The paper discusses factors affecting the corrosion behavior of the investigated coatings.
采用脉冲磁控溅射法制备了AlN、AlZrN和AlCrN薄膜。采用高速钢Т1、结构合金钢5140和结构碳钢1017作为衬底。通过改变磁控管电流、混合气体中的氮含量和衬底上的偏置电压，可以获得不同元素组成的纳米结构和非晶态涂层。对包被样品在3% NaCl溶液中进行伏安法和阻抗谱分析。涂层的腐蚀行为由腐蚀电流密度icorr、极化电阻Rp(腐蚀电位处)、比值icorr,s/icorr和Rp/Rp,s表征，其中下标s为基材。结果表明，除AlN外，所研究的涂层均具有电化学活性，腐蚀过程不仅发生在涂层不连续的基体上，也发生在涂层表面。结果表明，icorr为10−7 A cm−2的AlN/T1、AlZrN/5140、AlCrN/T1和AlCrN/5140涂层在3% NaCl中耐腐蚀性能最好。本文讨论了影响所研究涂层腐蚀行为的因素。
{"title":"Effect of structure, phase, and elemental composition of AlN, CrAlN, and ZrAlN coatings on their electrochemical behavior in 3% NaCl solution","authors":"A. Kameneva, V. Kichigin, N. Bublik","doi":"10.1002/maco.202213073","DOIUrl":"https://doi.org/10.1002/maco.202213073","url":null,"abstract":"Thin coatings AlN, AlZrN, and AlCrN were deposited by pulsed magnetron sputtering. The high‐speed steel Т1, structural alloy steel 5140, and structural carbon steel 1017 were used as substrates. The magnetron current, nitrogen content in the gas mixture, and bias voltage on the substrate were changed to obtain nanostructured and amorphous layers of coatings with different elemental compositions. The voltammetry and impedance spectroscopy were performed on the coated samples in 3% NaCl solution. The corrosion behavior of the coatings was characterized by the corrosion current density icorr, the polarization resistance Rp (at the corrosion potential), the ratios icorr,s/icorr, and Rp/Rp,s, where subscript s refers to the substrate. It was shown that the coatings under study (except AlN) are electrochemically active, and the corrosion processes occur not only on the substrate in the coating discontinuity but on the coating surface as well. The coatings AlN/T1, AlZrN/5140, AlCrN/T1, and AlCrN/5140 with icorr ~ 10−7 A cm−2 are found to be the most corrosion‐resistant in 3% NaCl. The paper discusses factors affecting the corrosion behavior of the investigated coatings.","PeriodicalId":18223,"journal":{"name":"Materials and Corrosion","volume":"30 1","pages":"1308 - 1317"},"PeriodicalIF":0.0,"publicationDate":"2022-03-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84466683","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In the present work, the Cr–AlSi12 composite coatings were successfully synthesized on the Ti–6Al–4V alloy substrate by using the mechanical alloying method. The effects of raw Cr particle size, milling duration, and annealing treatment on the preparation of the coatings were investigated. The as‐prepared coatings consisted of the inner coating layer with coarse Cr particles and the outer coating layer with refined and highly homogenized structure. The annealing treatment could promote element diffusion and alloying; it was favorable to the densification and oxidation resistance of the coatings. There is a highly densified alloyed layer in the outer coating. The annealed coating showed excellent friction and wear resistance. After the oxidation process, the annealed coating showed the best high‐temperature oxidation resistance. The oxidized annealed coating exhibited four layers, which included the thin Al2O3 oxide film, the homogenized alloyed layer, the composite layer consisted of Al2O3 and coarse Cr particles surrounded by alloyed layer, and the Al3Ti diffusion layer. This was favorable to the improvement of high‐temperature oxidation resistance. The oxidation process of the annealed coating was elaborated.
{"title":"High‐temperature corrosion of mechanically alloyed Cr–AlSi12 composite coatings on Ti–6Al–4V alloy substrate","authors":"Jiangzhong Jiang, Xiaomei Feng, Yifu Shen","doi":"10.1002/maco.202113008","DOIUrl":"https://doi.org/10.1002/maco.202113008","url":null,"abstract":"In the present work, the Cr–AlSi12 composite coatings were successfully synthesized on the Ti–6Al–4V alloy substrate by using the mechanical alloying method. The effects of raw Cr particle size, milling duration, and annealing treatment on the preparation of the coatings were investigated. The as‐prepared coatings consisted of the inner coating layer with coarse Cr particles and the outer coating layer with refined and highly homogenized structure. The annealing treatment could promote element diffusion and alloying; it was favorable to the densification and oxidation resistance of the coatings. There is a highly densified alloyed layer in the outer coating. The annealed coating showed excellent friction and wear resistance. After the oxidation process, the annealed coating showed the best high‐temperature oxidation resistance. The oxidized annealed coating exhibited four layers, which included the thin Al2O3 oxide film, the homogenized alloyed layer, the composite layer consisted of Al2O3 and coarse Cr particles surrounded by alloyed layer, and the Al3Ti diffusion layer. This was favorable to the improvement of high‐temperature oxidation resistance. The oxidation process of the annealed coating was elaborated.","PeriodicalId":18223,"journal":{"name":"Materials and Corrosion","volume":"51 1","pages":"1248 - 1264"},"PeriodicalIF":0.0,"publicationDate":"2022-03-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88440149","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A. N. Dobrotvorskaia, M. A. Dobrotvorskii, É. P. Shevyakova, M. A. Simanov
This study investigates the damage, microstructure, and mechanical evolution of service‐exposed HP40NbTi radiant tubes of a steam reformer furnace. Tube failure was reported after 6‐year of working at 525°C–830°C in the form of visible longitudinal and transverse cracks. The microstructure was evaluated using optical and scanning electron microscopy equipped with energy‐dispersive X‐ray spectrum analysis. The carbide phase transformation was determined by the method based on the matrix dissolution technique and X‐ray diffraction. The results of this study showed that the primary cause of the longitudinal crack formation is the local overheating and the oxidation of the dendritic grain boundaries. The M7C3 carbide transforms completely into the metastable M23C6 phase during high‐temperature service. Metallographic examinations revealed the shrinkage cavities and creep voids that are nucleated on both Cr‐ and Nb‐carbides. The continuous oxide layers of Cr2O3 and SiO2 formed near the inner and outer tube surfaces and the matrix's chemical composition near the outer tube surface was found to be depleted of Cr and C. Mechanical properties are irregular across the samples. A little margin of safety is noted, while the complete ductility dip is detected at room temperature. The root cause analysis of the failure under investigation showed that the tube failed due to the creep.
{"title":"Failure cause assessment of steam reformer radiant tube after long‐term service","authors":"A. N. Dobrotvorskaia, M. A. Dobrotvorskii, É. P. Shevyakova, M. A. Simanov","doi":"10.1002/maco.202213068","DOIUrl":"https://doi.org/10.1002/maco.202213068","url":null,"abstract":"This study investigates the damage, microstructure, and mechanical evolution of service‐exposed HP40NbTi radiant tubes of a steam reformer furnace. Tube failure was reported after 6‐year of working at 525°C–830°C in the form of visible longitudinal and transverse cracks. The microstructure was evaluated using optical and scanning electron microscopy equipped with energy‐dispersive X‐ray spectrum analysis. The carbide phase transformation was determined by the method based on the matrix dissolution technique and X‐ray diffraction. The results of this study showed that the primary cause of the longitudinal crack formation is the local overheating and the oxidation of the dendritic grain boundaries. The M7C3 carbide transforms completely into the metastable M23C6 phase during high‐temperature service. Metallographic examinations revealed the shrinkage cavities and creep voids that are nucleated on both Cr‐ and Nb‐carbides. The continuous oxide layers of Cr2O3 and SiO2 formed near the inner and outer tube surfaces and the matrix's chemical composition near the outer tube surface was found to be depleted of Cr and C. Mechanical properties are irregular across the samples. A little margin of safety is noted, while the complete ductility dip is detected at room temperature. The root cause analysis of the failure under investigation showed that the tube failed due to the creep.","PeriodicalId":18223,"journal":{"name":"Materials and Corrosion","volume":"6 1","pages":"1265 - 1273"},"PeriodicalIF":0.0,"publicationDate":"2022-03-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80476283","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Xiaodan Lv, Shuhui Liu, H. Xie, Qingming Cao, Chengdong Zhang, Fanwei Chen, Bin Liu
AMg61 (Al‐6.2% Mg), a novel form of high‐strength, high‐magnesium‐content aluminum alloy, has been developed for specific maritime engineering in recent years, while its corrosion behavior in seawater is still unknown. Therefore, the corrosion behavior of AMg61 in the simulated seawater was investigated herein, using a weight‐loss test and different electrochemical measurements. In addition, corrosion morphology and chemical contents were characterized by metallography, scanning electron microscopy, and energy‐dispersive spectroscopy. The results demonstrated that intergranular corrosion and microcracks developed first in the second phase of AMg61, followed by pitting corrosion. The matrix of AMg61, on the other hand, exhibited a uniform and exfoliation corrosion. The corrosion rate gradually decreased over time.
{"title":"Corrosion behavior of a newly developed high strength aluminum alloy with high magnesium content under simulated seawater environment","authors":"Xiaodan Lv, Shuhui Liu, H. Xie, Qingming Cao, Chengdong Zhang, Fanwei Chen, Bin Liu","doi":"10.1002/maco.202213065","DOIUrl":"https://doi.org/10.1002/maco.202213065","url":null,"abstract":"AMg61 (Al‐6.2% Mg), a novel form of high‐strength, high‐magnesium‐content aluminum alloy, has been developed for specific maritime engineering in recent years, while its corrosion behavior in seawater is still unknown. Therefore, the corrosion behavior of AMg61 in the simulated seawater was investigated herein, using a weight‐loss test and different electrochemical measurements. In addition, corrosion morphology and chemical contents were characterized by metallography, scanning electron microscopy, and energy‐dispersive spectroscopy. The results demonstrated that intergranular corrosion and microcracks developed first in the second phase of AMg61, followed by pitting corrosion. The matrix of AMg61, on the other hand, exhibited a uniform and exfoliation corrosion. The corrosion rate gradually decreased over time.","PeriodicalId":18223,"journal":{"name":"Materials and Corrosion","volume":"5 1","pages":"1318 - 1329"},"PeriodicalIF":0.0,"publicationDate":"2022-03-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75325483","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Masthead: Materials and Corrosion. 3/2022","authors":"","doi":"10.1002/maco.202270032","DOIUrl":"https://doi.org/10.1002/maco.202270032","url":null,"abstract":"","PeriodicalId":18223,"journal":{"name":"Materials and Corrosion","volume":"21 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2022-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86299154","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Dunja Marunkić, B. Jegdić, Jovana Pejić, Milena Milošević, A. Marinković, Bojana M. Radojković
The new environmentally friendly corrosion inhibitor Ce‐citrate was analyzed in 0.05 M NaCl solution on the AISI 4130 steel. For comparison, corrosion inhibitor Ce‐chloride is tested in the same concentration as Ce‐citrate (0.3 mM). Inhibitor efficiencies were determined by applying electrochemical impedance spectroscopy and potentiodynamic polarization measurements. The results of electrochemical measurements, the contact angle measurements, as well as the surface appearance of the specimens after the immersion in the inhibitive NaCl solution for 96 h confirmed that the new environmentally friendly inhibitor (Ce‐citrate) has a significantly higher protective ability than the Ce‐chloride. The protective ability of Ce‐citrate increases over time, according to the proposed mechanism of its action. In the inhibitive layer formed in NaCl solution containing Ce‐citrate, XPS analysis revealed the presence of cerium in oxidation states CeIII and CeIV, citrate anions (carboxyl O–C═O group as well as C–OH and C–C and C–H bonds), oxide, hydroxide, and oxyhydroxide of iron (mainly FeOOH and Fe2O3). The mechanism of inhibitory action of Ce‐citrate was proposed and analyzed in detail.
在0.05 M NaCl溶液中对新型环保型缓蚀剂柠檬酸铈(Ce‐citrate)在AISI 4130钢上进行了分析。为了进行比较，缓蚀剂氯化铈在与柠檬酸铈(0.3 mM)相同浓度下进行测试。通过电化学阻抗谱和动电位极化测量来确定缓蚀剂的效率。电化学测量、接触角测量以及样品在NaCl溶液中浸泡96 h后的表面形貌均证实了新型环保型缓蚀剂(柠檬酸铈)的保护能力明显高于氯化铈。根据提出的作用机制，柠檬酸铈的保护能力随着时间的推移而增加。在含有柠檬酸Ce的NaCl溶液中形成的抑制层中，XPS分析发现铈在氧化态CeIII和CeIV、柠檬酸阴离子(羧基O - c = O基团以及C-OH和C-C和C-H键)、铁的氧化物、氢氧化物和氢氧化物(主要是FeOOH和Fe2O3)中存在。提出并详细分析了柠檬酸铈的抑制作用机理。
{"title":"Analysis of inhibitory properties of Ce‐citrate as a green corrosion inhibitor of low alloy steel in neutral chloride solution","authors":"Dunja Marunkić, B. Jegdić, Jovana Pejić, Milena Milošević, A. Marinković, Bojana M. Radojković","doi":"10.1002/maco.202213079","DOIUrl":"https://doi.org/10.1002/maco.202213079","url":null,"abstract":"The new environmentally friendly corrosion inhibitor Ce‐citrate was analyzed in 0.05 M NaCl solution on the AISI 4130 steel. For comparison, corrosion inhibitor Ce‐chloride is tested in the same concentration as Ce‐citrate (0.3 mM). Inhibitor efficiencies were determined by applying electrochemical impedance spectroscopy and potentiodynamic polarization measurements. The results of electrochemical measurements, the contact angle measurements, as well as the surface appearance of the specimens after the immersion in the inhibitive NaCl solution for 96 h confirmed that the new environmentally friendly inhibitor (Ce‐citrate) has a significantly higher protective ability than the Ce‐chloride. The protective ability of Ce‐citrate increases over time, according to the proposed mechanism of its action. In the inhibitive layer formed in NaCl solution containing Ce‐citrate, XPS analysis revealed the presence of cerium in oxidation states CeIII and CeIV, citrate anions (carboxyl O–C═O group as well as C–OH and C–C and C–H bonds), oxide, hydroxide, and oxyhydroxide of iron (mainly FeOOH and Fe2O3). The mechanism of inhibitory action of Ce‐citrate was proposed and analyzed in detail.","PeriodicalId":18223,"journal":{"name":"Materials and Corrosion","volume":"118 1","pages":"1286 - 1297"},"PeriodicalIF":0.0,"publicationDate":"2022-02-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81780177","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The high‐temperature sulfur corrosion resistance of S30432 and TP310HCbN typically used in the superheater and reheater of a 620°C ultra‐supercritical boiler is investigated in this study. Samples coated with coal ash are placed in a device filled with simulated flue gas at 650°C and 700°C, respectively, for 2000 h. The samples are then analyzed through X‐ray diffraction, scanning electron microscopy, and energy‐dispersive spectroscopy. S30432 is mainly oxidized under 650°C and 0.2% SO2 volume concentration, and the weight reduction is 6.6 mg cm−2. However, under 700°C and 0.3% SO2 volume concentration, severe sulfidation reaction occurs, sharply accelerating high‐temperature corrosion. As a result, weight reduction up to 41.8 mg cm−2 occurs. Although sulfidation reaction also occurs in TP310HCbN, there is no serious corrosion; the corrosion rate reduces in the later stages of the experiment, and a weight increase of 2.4 mg cm−2 is observed. After 11 520 h of the actual operation of the 1000 MW 620°C boiler, there is no obvious high‐temperature corrosion in the high‐temperature areas without coke‐block adhesion. These results indicate that S30432 and TP310HCbN satisfy the requirements of 620°C ultra‐supercritical boilers burning high‐sulfur coal.
{"title":"High‐temperature corrosion behavior of S30432 and TP310HCbN coatings in simulated 620°C ultra‐supercritical boiler coal ash/gas environment","authors":"Yugang Liu, Yinhe Liu, Chunhong Mo, Minqiang Zhang, Meng Dong, Shaocheng Pan, Shenming Ran","doi":"10.1002/maco.202113014","DOIUrl":"https://doi.org/10.1002/maco.202113014","url":null,"abstract":"The high‐temperature sulfur corrosion resistance of S30432 and TP310HCbN typically used in the superheater and reheater of a 620°C ultra‐supercritical boiler is investigated in this study. Samples coated with coal ash are placed in a device filled with simulated flue gas at 650°C and 700°C, respectively, for 2000 h. The samples are then analyzed through X‐ray diffraction, scanning electron microscopy, and energy‐dispersive spectroscopy. S30432 is mainly oxidized under 650°C and 0.2% SO2 volume concentration, and the weight reduction is 6.6 mg cm−2. However, under 700°C and 0.3% SO2 volume concentration, severe sulfidation reaction occurs, sharply accelerating high‐temperature corrosion. As a result, weight reduction up to 41.8 mg cm−2 occurs. Although sulfidation reaction also occurs in TP310HCbN, there is no serious corrosion; the corrosion rate reduces in the later stages of the experiment, and a weight increase of 2.4 mg cm−2 is observed. After 11 520 h of the actual operation of the 1000 MW 620°C boiler, there is no obvious high‐temperature corrosion in the high‐temperature areas without coke‐block adhesion. These results indicate that S30432 and TP310HCbN satisfy the requirements of 620°C ultra‐supercritical boilers burning high‐sulfur coal.","PeriodicalId":18223,"journal":{"name":"Materials and Corrosion","volume":"32 1","pages":"1222 - 1235"},"PeriodicalIF":0.0,"publicationDate":"2022-02-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89959922","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
R. Baldan, L. Latu-Romain, Y. Wouters, N. Chaia, L. B. Alkmin, A. M. S. Sousa Malafaia
Superalloys are widely employed at high temperatures for structural applications. Hence, knowledge about the oxidation of these materials is essential. However, the literature is scanty when it comes to some families of superalloys. The purpose of this study was therefore to analyze the MAR‐M246 polycrystalline alloy in isothermal short‐term tests at 800°C and 1000°C for up to 240 h. Thermodynamic simulations were performed to evaluate the material's phase stability as a function of temperature and to assess the expected phases in response to oxygen pressure. The oxidized samples were characterized by SEM‐EDS and DRX, which revealed a tendency for scaling of oxidized material, particularly at temperatures of 1000°C. Nevertheless, protective layers of Cr2O3 and Al2O3 oxides were formed, which enabled the formation of fairly thin oxide layers, in addition to NiO and complex oxides. The region of the metallic substrate close to the oxide layer underwent aluminum depletion, causing the gamma‐prime phase to disappear, as well as formation of aluminum oxides and titanium nitrides. Last, a good correlation was found between the thermodynamic simulations and the oxides that were formed.
{"title":"Isothermal short‐term oxidation behavior of MAR‐M246 nickel‐based superalloy at 800°C and 1000°C","authors":"R. Baldan, L. Latu-Romain, Y. Wouters, N. Chaia, L. B. Alkmin, A. M. S. Sousa Malafaia","doi":"10.1002/maco.202112931","DOIUrl":"https://doi.org/10.1002/maco.202112931","url":null,"abstract":"Superalloys are widely employed at high temperatures for structural applications. Hence, knowledge about the oxidation of these materials is essential. However, the literature is scanty when it comes to some families of superalloys. The purpose of this study was therefore to analyze the MAR‐M246 polycrystalline alloy in isothermal short‐term tests at 800°C and 1000°C for up to 240 h. Thermodynamic simulations were performed to evaluate the material's phase stability as a function of temperature and to assess the expected phases in response to oxygen pressure. The oxidized samples were characterized by SEM‐EDS and DRX, which revealed a tendency for scaling of oxidized material, particularly at temperatures of 1000°C. Nevertheless, protective layers of Cr2O3 and Al2O3 oxides were formed, which enabled the formation of fairly thin oxide layers, in addition to NiO and complex oxides. The region of the metallic substrate close to the oxide layer underwent aluminum depletion, causing the gamma‐prime phase to disappear, as well as formation of aluminum oxides and titanium nitrides. Last, a good correlation was found between the thermodynamic simulations and the oxides that were formed.","PeriodicalId":18223,"journal":{"name":"Materials and Corrosion","volume":"10 1","pages":"1236 - 1247"},"PeriodicalIF":0.0,"publicationDate":"2022-02-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82371313","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Mogomotsi Leshetla, D. Klenam, J. Merwe, Herman Potgieter, D. Whitefield, M. Bodunrin
In this study, experimental Ti–6Al–1V–3Fe, Ti–4.5Al–1V–3Fe, and Ti–3Fe alloys, as well as commercial Ti–6Al–4V alloy that were scaled up utilizing vacuum induction melting technology, were assessed for corrosion performance in simulated body fluids. The selected simulated body fluids were 0.9 wt% NaCl solution and Hanks balanced salt solution (HBSS). Open circuit potential and linear polarization scans were performed to understand the corrosion performance of the alloys. The surface of the alloys was examined before and after exposure to corrosive solutions using scanning electron microscopy. The results show that all the alloys exhibit good corrosion performance in simulated body fluids. The corrosion rates were less than 0.5 mm/year. Owing to higher corrosion potential and lower corrosion rate, Ti–6Al–1V–3Fe and Ti–4.5Al–1V–3Fe had the best resistance to corrosion in 0.9 wt% NaCl and HBSS, respectively. All the alloys consist of a fully lamellar structure with α and β phases. There was no evidence of severe deterioration on the exposed surface of alloys in the simulated body fluids.
{"title":"Corrosion resistance of iron‐containing experimental titanium alloys exposed to simulated body fluids","authors":"Mogomotsi Leshetla, D. Klenam, J. Merwe, Herman Potgieter, D. Whitefield, M. Bodunrin","doi":"10.1002/maco.202213076","DOIUrl":"https://doi.org/10.1002/maco.202213076","url":null,"abstract":"In this study, experimental Ti–6Al–1V–3Fe, Ti–4.5Al–1V–3Fe, and Ti–3Fe alloys, as well as commercial Ti–6Al–4V alloy that were scaled up utilizing vacuum induction melting technology, were assessed for corrosion performance in simulated body fluids. The selected simulated body fluids were 0.9 wt% NaCl solution and Hanks balanced salt solution (HBSS). Open circuit potential and linear polarization scans were performed to understand the corrosion performance of the alloys. The surface of the alloys was examined before and after exposure to corrosive solutions using scanning electron microscopy. The results show that all the alloys exhibit good corrosion performance in simulated body fluids. The corrosion rates were less than 0.5 mm/year. Owing to higher corrosion potential and lower corrosion rate, Ti–6Al–1V–3Fe and Ti–4.5Al–1V–3Fe had the best resistance to corrosion in 0.9 wt% NaCl and HBSS, respectively. All the alloys consist of a fully lamellar structure with α and β phases. There was no evidence of severe deterioration on the exposed surface of alloys in the simulated body fluids.","PeriodicalId":18223,"journal":{"name":"Materials and Corrosion","volume":"35 1","pages":"1298 - 1307"},"PeriodicalIF":0.0,"publicationDate":"2022-02-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79777240","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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