Gruson’s Fahrpanzer is a remarkable example of the military-technological changes occurring in the 19th century. It is a small and movable armour carriage for guns, i. e., an artillery piece shielded by armor. It was invented by Hermann Gruson and Maximilian Schumann and exported around the world. Even though the technical data had been documented extensively at the time, knowledge about the materials used and their mechanical properties have not survived. For this paper, one of Gruson’s Fahrpanzers was analyzed for the first time through materials science. The hypothesis that Gruson used his famous chilled cast iron for the Fahrpanzer could thus be refuted.
{"title":"Gruson’s Fahrpanzer – Historical insights thanks to non-destructive materials science","authors":"S. Dieck, M. Wilke, T. Halle, L. Strobach","doi":"10.1515/pm-2023-1068","DOIUrl":"https://doi.org/10.1515/pm-2023-1068","url":null,"abstract":"\u0000 Gruson’s Fahrpanzer is a remarkable example of the military-technological changes occurring in the 19th century. It is a small and movable armour carriage for guns, i. e., an artillery piece shielded by armor. It was invented by Hermann Gruson and Maximilian Schumann and exported around the world. Even though the technical data had been documented extensively at the time, knowledge about the materials used and their mechanical properties have not survived. For this paper, one of Gruson’s Fahrpanzers was analyzed for the first time through materials science. The hypothesis that Gruson used his famous chilled cast iron for the Fahrpanzer could thus be refuted.","PeriodicalId":20360,"journal":{"name":"Practical Metallography","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-04-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140657600","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}
B. S. Bindhushree, P. Sevvel, S. P. Shanmuganatan, D. Saravanabavan, M. Madhusudan
Cast alloys find suitable applicability in aerospace sector owing to low porosity, high specific strength, corrosion resistance, fluidity and good machinability. The investigation focuses on friction stir welding (FSW) of cast A356 and A2014 alloys with varied range of process parameters, namely tool pin shape (cylinder, threaded cylinder, square, and conical), tool rotation speed (1800–2100 rpm) and welding speed (10–25 mm × min−1). Experimentation on stirwelding was performed based on selected tool pin shape between varied tool rotation and welding speed. The output responses, namely Ultimate tensile strength (UTS) and micro hardness, have been evaluated to study the effect of each tool. The microstructural characteristics of the weld samples were analyzed using optical microscope and scanning electron microscope (SEM) technique. The microstructural observation unveiled that complete fusion prevails between the parent alloys devoid of micro porosities and segregations. The re-crystallization effect resulted in the finer grains. The cylinder-shaped tool with a thread and square shaped tool rendered better strength and hardness properties of 136.6 MPa and 109.4 HV, respectively.
{"title":"Influence of tool geometry on mechanical and microstructural characteristics of friction stir welded cast alloys","authors":"B. S. Bindhushree, P. Sevvel, S. P. Shanmuganatan, D. Saravanabavan, M. Madhusudan","doi":"10.1515/pm-2023-1055","DOIUrl":"https://doi.org/10.1515/pm-2023-1055","url":null,"abstract":"\u0000 Cast alloys find suitable applicability in aerospace sector owing to low porosity, high specific strength, corrosion resistance, fluidity and good machinability. The investigation focuses on friction stir welding (FSW) of cast A356 and A2014 alloys with varied range of process parameters, namely tool pin shape (cylinder, threaded cylinder, square, and conical), tool rotation speed (1800–2100 rpm) and welding speed (10–25 mm × min−1). Experimentation on stirwelding was performed based on selected tool pin shape between varied tool rotation and welding speed. The output responses, namely Ultimate tensile strength (UTS) and micro hardness, have been evaluated to study the effect of each tool. The microstructural characteristics of the weld samples were analyzed using optical microscope and scanning electron microscope (SEM) technique. The microstructural observation unveiled that complete fusion prevails between the parent alloys devoid of micro porosities and segregations. The re-crystallization effect resulted in the finer grains. The cylinder-shaped tool with a thread and square shaped tool rendered better strength and hardness properties of 136.6 MPa and 109.4 HV, respectively.","PeriodicalId":20360,"journal":{"name":"Practical Metallography","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-04-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140654602","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}
High-strength HV-fastener sets of dimensions M48 and M64 with property class 10.9 were employed in offshore wind turbine frameworks. The M64 were used in coupling flanges within monopiles. The M48 were employed in another offshore wind farm and encountered natural weathering. In both installations, time-delayed fractures of the nuts were observed. Owing to the presence of macroscopically visible corrosion products, hydrogen-induced stress corrosion cracking (Hi-SCC) was established as the probable cause of failure. However, a nut fracture in a properly pre-tensioned bolt assembly is atypical since the stresses in the bolt threads are higher than those in the nuts. Based on the Hi-SCC theory, the fracture should occur at the most stressed component, which is the bolt. During the root cause analysis, extensive examinations were conducted to determine the cause of the nut fractures. The focus was on investigating whether the nut material was more prone to Hi-SCC than the bolt material. The examination program included scanning electron microscopy and energy dispersive x-ray spectroscopy (SEM-EDS) analysis of the fracture surfaces, optical microscopy of microspecimens, mechanical tests, and stress rupture tests of hydrogen-charged specimens. While the results suggest that the tested nuts comply with the requirements of the applicable standards regarding material properties, they also reveal that the nut material is, despite its lower tensile strength, significantly more susceptible to Hi-SCC than the bolt material. Therefore, a direct relationship between material susceptibility to Hi-SCC and the tensile strength, as standards and guidelines imply, is not given.
{"title":"Enhanced susceptibility of high-strength fastener nuts to hydrogen-induced stress corrosion cracking","authors":"H. Hoche, M. Brilz, M. Oechsner","doi":"10.1515/pm-2024-0027","DOIUrl":"https://doi.org/10.1515/pm-2024-0027","url":null,"abstract":"\u0000 High-strength HV-fastener sets of dimensions M48 and M64 with property class 10.9 were employed in offshore wind turbine frameworks. The M64 were used in coupling flanges within monopiles. The M48 were employed in another offshore wind farm and encountered natural weathering. In both installations, time-delayed fractures of the nuts were observed. Owing to the presence of macroscopically visible corrosion products, hydrogen-induced stress corrosion cracking (Hi-SCC) was established as the probable cause of failure. However, a nut fracture in a properly pre-tensioned bolt assembly is atypical since the stresses in the bolt threads are higher than those in the nuts. Based on the Hi-SCC theory, the fracture should occur at the most stressed component, which is the bolt.\u0000 During the root cause analysis, extensive examinations were conducted to determine the cause of the nut fractures. The focus was on investigating whether the nut material was more prone to Hi-SCC than the bolt material. The examination program included scanning electron microscopy and energy dispersive x-ray spectroscopy (SEM-EDS) analysis of the fracture surfaces, optical microscopy of microspecimens, mechanical tests, and stress rupture tests of hydrogen-charged specimens. While the results suggest that the tested nuts comply with the requirements of the applicable standards regarding material properties, they also reveal that the nut material is, despite its lower tensile strength, significantly more susceptible to Hi-SCC than the bolt material. Therefore, a direct relationship between material susceptibility to Hi-SCC and the tensile strength, as standards and guidelines imply, is not given.","PeriodicalId":20360,"journal":{"name":"Practical Metallography","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-04-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140653476","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}
Archeological finds, such as old coins among which some show signs of corrosion, are, in general, unique pieces even though several copies exist of individual types. Subferrati, Roman coins with an iron core and a bronze coating, for instance, could be examined by conventional computed tomography (CT). The CT image allows an easy distinction of corrosion products, metallic iron, and the bronze so that appropriate sections could be selected from the images for metallography. The micro-CT technology even allows examining smaller archaeological objects to get an overview. The resolution of the micro-CT is a function of the object size and lies between 5 and 10 μm. The following metallographic examinations are intended to characterize the microstructure. Apart from these examinations, SEM analyses may also be performed on the sections. Different bronze pieces from cremation and inhumation burials were examined. Micro-CT provides a well recognizable contrast between corrosion products and the metallic bronze. If several similar objects exist, micro-CT examinations allow a decision to be made on which parts are suitable for metallographic analyses and which are not.
{"title":"Examination of archaeological bronze parts using micro-computed tomography and metallography","authors":"R. Haubner, S. Strobl","doi":"10.1515/pm-2024-1054","DOIUrl":"https://doi.org/10.1515/pm-2024-1054","url":null,"abstract":"\u0000 Archeological finds, such as old coins among which some show signs of corrosion, are, in general, unique pieces even though several copies exist of individual types. Subferrati, Roman coins with an iron core and a bronze coating, for instance, could be examined by conventional computed tomography (CT). The CT image allows an easy distinction of corrosion products, metallic iron, and the bronze so that appropriate sections could be selected from the images for metallography.\u0000 The micro-CT technology even allows examining smaller archaeological objects to get an overview. The resolution of the micro-CT is a function of the object size and lies between 5 and 10 μm. The following metallographic examinations are intended to characterize the microstructure. Apart from these examinations, SEM analyses may also be performed on the sections.\u0000 Different bronze pieces from cremation and inhumation burials were examined. Micro-CT provides a well recognizable contrast between corrosion products and the metallic bronze.\u0000 If several similar objects exist, micro-CT examinations allow a decision to be made on which parts are suitable for metallographic analyses and which are not.","PeriodicalId":20360,"journal":{"name":"Practical Metallography","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-03-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140225072","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":"Obituary for Professor Dr. Günter Petzow","authors":"","doi":"10.1515/pm-2024-0023","DOIUrl":"https://doi.org/10.1515/pm-2024-0023","url":null,"abstract":"","PeriodicalId":20360,"journal":{"name":"Practical Metallography","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-03-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140226611","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}
B. Camin, C. Dinh, J. Streckenbach, M. Gille, E. Uhlmann
Carbide tool electrodes for electrical discharge drilling were subjected to heat treatment at various temperatures and in different atmospheres for the same duration, respectively, in order to reduce the electrical conductivity of the lateral surface. Hardness tests show that the heat treatment does not induce a loss of strength in the electrode body. Microscopic analyses revealed that the lateral surface, characterized by a two-layer structure comprising a surface and a diffusion layer of varying characteristics and morphology, such as surface roughness, degree of coverage, delaminations, or a columnar microstructure, changes. It is revealed that the electrical conductivity is a function of the total layer thickness made up of the thickness of the surface layer and a diffusion layer. The electrical conductivity drops with increasing total layer thickness. In the context of electric discharge drilling tests, it was found that the reduced electrical conductivity leads to a decreased material removal rate and a simultaneously reduced linear electrode wear. Heat treatments ensuring consistent erosion times resulted in a wear rate reduction of the tool electrodes of up to 10 %.
{"title":"Effect of the heat treatment on the microstructure of carbide tool electrodes for electrical discharge drilling","authors":"B. Camin, C. Dinh, J. Streckenbach, M. Gille, E. Uhlmann","doi":"10.1515/pm-2024-0020","DOIUrl":"https://doi.org/10.1515/pm-2024-0020","url":null,"abstract":"\u0000 Carbide tool electrodes for electrical discharge drilling were subjected to heat treatment at various temperatures and in different atmospheres for the same duration, respectively, in order to reduce the electrical conductivity of the lateral surface. Hardness tests show that the heat treatment does not induce a loss of strength in the electrode body. Microscopic analyses revealed that the lateral surface, characterized by a two-layer structure comprising a surface and a diffusion layer of varying characteristics and morphology, such as surface roughness, degree of coverage, delaminations, or a columnar microstructure, changes. It is revealed that the electrical conductivity is a function of the total layer thickness made up of the thickness of the surface layer and a diffusion layer. The electrical conductivity drops with increasing total layer thickness. In the context of electric discharge drilling tests, it was found that the reduced electrical conductivity leads to a decreased material removal rate and a simultaneously reduced linear electrode wear. Heat treatments ensuring consistent erosion times resulted in a wear rate reduction of the tool electrodes of up to 10 %.","PeriodicalId":20360,"journal":{"name":"Practical Metallography","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-03-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140227856","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}
Heat treatment (HT) problems, or the lack of necessary HT, are a regular topic of discussion in the papers published in this section Failure Analysis of Practical Metallography. In this present contribution, a case study is presented that shows how an erroneous furnace run almost caused the scrapping of an entire engine set of Metallic Heat Shields (MHS) of a heavy-duty gas turbine engine. The authors readily admit that the subject components did not fail. They were not even put in engine service yet. That means that this case study does not describe a failure in the original sense of the word. However, from a metallurgical point of view, it is still an interesting case that shows that without proper scrutiny during metallurgical investigation in the laboratory, considerable economic loss could have resulted from a simple fabrication problem, that involved a malfunctioning control system of a heat treatment furnace. It was concluded from the metallurgical investigation that is the subject of this contribution that an almost tripled soaking time during aging, i. e., precipitation hardening, of an entire engine set of MHS did not cause any microstructural alterations that could have detrimentally affected mechanical properties of the subject components.
{"title":"Metallographic characterization of metallic heat shields, accidentally precipitation-hardened with tripled soaking time","authors":"A. Neidel, B. Fischer, J. Rockel","doi":"10.1515/pm-2024-0021","DOIUrl":"https://doi.org/10.1515/pm-2024-0021","url":null,"abstract":"\u0000 Heat treatment (HT) problems, or the lack of necessary HT, are a regular topic of discussion in the papers published in this section Failure Analysis of Practical Metallography. In this present contribution, a case study is presented that shows how an erroneous furnace run almost caused the scrapping of an entire engine set of Metallic Heat Shields (MHS) of a heavy-duty gas turbine engine. The authors readily admit that the subject components did not fail. They were not even put in engine service yet. That means that this case study does not describe a failure in the original sense of the word. However, from a metallurgical point of view, it is still an interesting case that shows that without proper scrutiny during metallurgical investigation in the laboratory, considerable economic loss could have resulted from a simple fabrication problem, that involved a malfunctioning control system of a heat treatment furnace. It was concluded from the metallurgical investigation that is the subject of this contribution that an almost tripled soaking time during aging, i. e., precipitation hardening, of an entire engine set of MHS did not cause any microstructural alterations that could have detrimentally affected mechanical properties of the subject components.","PeriodicalId":20360,"journal":{"name":"Practical Metallography","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-03-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140225580","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}
K. Du, Z. Zhang, S. You, X. Zuo, B. Zheng, Y. Ren, L. Sun, W. Zheng, H. Huang, X. Yuan
The corrosion process of Q345 steel in simulated industrial atmospheric surroundings using NaHSO3 as the corrosion medium was performed. Corrosion weight loss, X-ray diffraction (XRD), electron probe microanalysis (EPMA), laser scanning confocal microscopy (LSCM), and scanning electron microscopy (SEM) were utilized to investigate the corrosion behavior of Q345 steel samples at various corrosion times. The results indicate that, in the industrial atmospheric acceleration system, the corrosion law of Q345 steel follows an exponential function model and that as the corrosion period lengthens, the rate of corrosion declines steadily. γ-FeOOH, α-FeOOH, Fe3O4, Fe3O2, and FeO make up the majority of the corrosion products on the surface of rust layer, and the rust layer structure is generally loose in the first stages of corrosion. As the corrosion time lengthens, the corrosion products transform from needle-like to cluster-like and the rust layer will become thicker. In addition, there is a segregation of the elements Cr, S, and O in the rust layer of Q345 steel.
{"title":"Corrosion behavior of Q345 steel in a simulated industrial atmosphere","authors":"K. Du, Z. Zhang, S. You, X. Zuo, B. Zheng, Y. Ren, L. Sun, W. Zheng, H. Huang, X. Yuan","doi":"10.1515/pm-2023-1065","DOIUrl":"https://doi.org/10.1515/pm-2023-1065","url":null,"abstract":"\u0000 The corrosion process of Q345 steel in simulated industrial atmospheric surroundings using NaHSO3 as the corrosion medium was performed. Corrosion weight loss, X-ray diffraction (XRD), electron probe microanalysis (EPMA), laser scanning confocal microscopy (LSCM), and scanning electron microscopy (SEM) were utilized to investigate the corrosion behavior of Q345 steel samples at various corrosion times. The results indicate that, in the industrial atmospheric acceleration system, the corrosion law of Q345 steel follows an exponential function model and that as the corrosion period lengthens, the rate of corrosion declines steadily. γ-FeOOH, α-FeOOH, Fe3O4, Fe3O2, and FeO make up the majority of the corrosion products on the surface of rust layer, and the rust layer structure is generally loose in the first stages of corrosion. As the corrosion time lengthens, the corrosion products transform from needle-like to cluster-like and the rust layer will become thicker. In addition, there is a segregation of the elements Cr, S, and O in the rust layer of Q345 steel.","PeriodicalId":20360,"journal":{"name":"Practical Metallography","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-01-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139597685","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 hitch pin is a critical component between tractor and trailer. The failure of hitch pins is quite frequent and a serious issue which remains unaddressed to a great extent due to limited information on this topic. This paper presents a novel insight into substandard pins manufactured in the informal sector due to non-conformance to any established standard and opens up a new area for further research on this subject. In the present context, risk factors along with reasons of cracks of in-service hitch pins were assessed to enhance the safety of humans. The pin showed signs of a crack, corrosion, scratches, and dents. Notches and scratches acted as stress raisers. Cracks can be seen initiating from the tip of notches. The pin was made of non-standard mild steel and was not heat treated. The study further demonstrates the methods to improve the fatigue life of the pin using numerical simulation. The hardness method was used to collect the cyclic fatigue properties of the commercially available mild steel for different heat-treated samples using the strain life fatigue approach. The casehardened mild steel pin of a case depth of 1.3 mm with a hardness of 30 HRC had considerably increased fatigue properties. Recommendations have been provided to protect humans from these accidents.
{"title":"Risk assessment of hitch pins connecting tractor and trailer to enhance the safety of humans using strain life fatigue approach","authors":"S. Chopra, P. Kumar, M. Kumar","doi":"10.1515/pm-2023-1045","DOIUrl":"https://doi.org/10.1515/pm-2023-1045","url":null,"abstract":"\u0000 The hitch pin is a critical component between tractor and trailer. The failure of hitch pins is quite frequent and a serious issue which remains unaddressed to a great extent due to limited information on this topic. This paper presents a novel insight into substandard pins manufactured in the informal sector due to non-conformance to any established standard and opens up a new area for further research on this subject. In the present context, risk factors along with reasons of cracks of in-service hitch pins were assessed to enhance the safety of humans. The pin showed signs of a crack, corrosion, scratches, and dents. Notches and scratches acted as stress raisers. Cracks can be seen initiating from the tip of notches. The pin was made of non-standard mild steel and was not heat treated. The study further demonstrates the methods to improve the fatigue life of the pin using numerical simulation. The hardness method was used to collect the cyclic fatigue properties of the commercially available mild steel for different heat-treated samples using the strain life fatigue approach. The casehardened mild steel pin of a case depth of 1.3 mm with a hardness of 30 HRC had considerably increased fatigue properties. Recommendations have been provided to protect humans from these accidents.","PeriodicalId":20360,"journal":{"name":"Practical Metallography","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-01-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139596085","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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