Abstract In metallography, the choice of the right etchant is crucial for visualizing the microstructure. As conventional etching agents generally contain a more or less high proportion of hazardous substances that need to be reduced in the future, examples are given of how this reduction is possible in principle. This reduction in hazardous substances is mainly achieved through microscopy contrasts, dilution of etching solutions and electrolytic etching.
{"title":"Less is sometimes more – some examples of the reduction of hazardous substances in metallographic etching","authors":"H. Schnarr","doi":"10.1515/pm-2024-0038","DOIUrl":"https://doi.org/10.1515/pm-2024-0038","url":null,"abstract":"Abstract In metallography, the choice of the right etchant is crucial for visualizing the microstructure. As conventional etching agents generally contain a more or less high proportion of hazardous substances that need to be reduced in the future, examples are given of how this reduction is possible in principle. This reduction in hazardous substances is mainly achieved through microscopy contrasts, dilution of etching solutions and electrolytic etching.","PeriodicalId":508095,"journal":{"name":"Practical Metallography","volume":"157 2","pages":"420 - 446"},"PeriodicalIF":0.0,"publicationDate":"2024-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141692876","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}
All the jaws of a four-jaw chuck mounted on the faceplate of a large lathe were received by the material testing laboratory to undergo metallurgical failure analysis. Each of the four jaws exhibited cracks in the fillet radius between one of the gripping surfaces and the long horizontal part. The cracks were just visible to the unaided eye und had been discovered by an alert mechanic. One of the jaws was selected for further material analysis for which the crack was opened to undergo fractographic evaluation. The analysis also involved the evaluation of the material using optical emission spectrometry, the preparation of a metallographic sample, and hardness testing. The cracks occurred as a result of repeated overload at the crack initiation sites located in the fillet radius. This was not a single overload event which would not have caused the jaws to crack, but a series of overload events. The situation did not pose a safety hazard to the staff since the soft and tough core of the case-hardened jaws would have retarded, if not stopped, crack growth. A sudden disastrous failure of the jaws by breaking off, for example, and extremely heavy components crashing down as a result were not an imminent threat. This dangerous failure scenario would have been enabled if the jaws had been through-hardened. Instead, casehardening heat treatment had been applied which is the correct choice for this type of component.
{"title":"Do cracked jaws of the four-jaw chuck of a large lathe pose a danger?","authors":"J. Rockel, E. Cagliyan, B. Fischer, A. Neidel","doi":"10.1515/pm-2024-0048","DOIUrl":"https://doi.org/10.1515/pm-2024-0048","url":null,"abstract":"\u0000 All the jaws of a four-jaw chuck mounted on the faceplate of a large lathe were received by the material testing laboratory to undergo metallurgical failure analysis. Each of the four jaws exhibited cracks in the fillet radius between one of the gripping surfaces and the long horizontal part. The cracks were just visible to the unaided eye und had been discovered by an alert mechanic. One of the jaws was selected for further material analysis for which the crack was opened to undergo fractographic evaluation. The analysis also involved the evaluation of the material using optical emission spectrometry, the preparation of a metallographic sample, and hardness testing. The cracks occurred as a result of repeated overload at the crack initiation sites located in the fillet radius. This was not a single overload event which would not have caused the jaws to crack, but a series of overload events. The situation did not pose a safety hazard to the staff since the soft and tough core of the case-hardened jaws would have retarded, if not stopped, crack growth. A sudden disastrous failure of the jaws by breaking off, for example, and extremely heavy components crashing down as a result were not an imminent threat. This dangerous failure scenario would have been enabled if the jaws had been through-hardened. Instead, casehardening heat treatment had been applied which is the correct choice for this type of component.","PeriodicalId":508095,"journal":{"name":"Practical Metallography","volume":"108 4","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141842306","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 fractured transition side seal retainer, together with an intact piece for reference, was received from the client on December of 2023. The subject part fractured next to the fastening hole, liberating a long ligament that was never found but reportedly caused some damage to hot gas path components downstream of a large gas turbine engine. It is speculated that the subject side seal retainer fractured due to high-stress, not fully reversed bending high cycle fatigue failure. It is recommended to make the design sturdier by considering dampening the long free length of the part, and by specifying a larger fillet radius in the initiation area. Also, over-torquing upon assembly of the subject part should be avoided.
{"title":"What if fractography does not tell us anything? – Failure of a side seal retainer","authors":"B. Fischer, M. Giller, E. Cagliyan, A. Neidel","doi":"10.1515/pm-2024-0047","DOIUrl":"https://doi.org/10.1515/pm-2024-0047","url":null,"abstract":"\u0000 A fractured transition side seal retainer, together with an intact piece for reference, was received from the client on December of 2023. The subject part fractured next to the fastening hole, liberating a long ligament that was never found but reportedly caused some damage to hot gas path components downstream of a large gas turbine engine. It is speculated that the subject side seal retainer fractured due to high-stress, not fully reversed bending high cycle fatigue failure. It is recommended to make the design sturdier by considering dampening the long free length of the part, and by specifying a larger fillet radius in the initiation area. Also, over-torquing upon assembly of the subject part should be avoided.","PeriodicalId":508095,"journal":{"name":"Practical Metallography","volume":"13 12","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141844663","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":"Interview with Dr. Volker Hinrichs","authors":"","doi":"10.1515/pm-2024-0051","DOIUrl":"https://doi.org/10.1515/pm-2024-0051","url":null,"abstract":"","PeriodicalId":508095,"journal":{"name":"Practical Metallography","volume":"126 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141853138","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}
Abstract This article shows how conventional etching methods can be replaced by electrolytic processes, thereby reducing hazardous substances during etching. The joint experiment carried out on this topic by the “Sample Preparation” working group uses various materials to show how hazardous substances can be reduced, but also the existing limitations.
{"title":"Collaborative experiment of the work group “Sample Preparation” on the subject “Reduction of hazardous substances in metallographic etching using electrolytic etching techniques”","authors":"H. Schnarr","doi":"10.1515/pm-2024-0040","DOIUrl":"https://doi.org/10.1515/pm-2024-0040","url":null,"abstract":"Abstract This article shows how conventional etching methods can be replaced by electrolytic processes, thereby reducing hazardous substances during etching. The joint experiment carried out on this topic by the “Sample Preparation” working group uses various materials to show how hazardous substances can be reduced, but also the existing limitations.","PeriodicalId":508095,"journal":{"name":"Practical Metallography","volume":"4 11‐12","pages":"458 - 496"},"PeriodicalIF":0.0,"publicationDate":"2024-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141715695","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}
Abstract The article describes various modifications of Klemm etching solutions and their applications to different materials. In addition to classic immersion etching, electrolytic etching is also used for the first time, demonstrating the potential of this etching method based on sodium thiosulfate and potassium metabisulfide for other materials.
{"title":"Potential applications for modified Klemmsolutions","authors":"H. Schnarr","doi":"10.1515/pm-2024-0039","DOIUrl":"https://doi.org/10.1515/pm-2024-0039","url":null,"abstract":"Abstract The article describes various modifications of Klemm etching solutions and their applications to different materials. In addition to classic immersion etching, electrolytic etching is also used for the first time, demonstrating the potential of this etching method based on sodium thiosulfate and potassium metabisulfide for other materials.","PeriodicalId":508095,"journal":{"name":"Practical Metallography","volume":"108 7","pages":"447 - 457"},"PeriodicalIF":0.0,"publicationDate":"2024-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141713249","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}
Hydrocarbon leaks were repeatedly found in the client’s refinery. Because of the recurring nature of this failure, the operator approached the authors’ laboratory to get a second opinion on the metallurgical root cause of the failure. It was known from the customer that corrosive species, such as ammonium chloride salt precipitates, are present in the subject diesel hydrotreating unit (DHT). From the findings obtained in the investigation that is the subject of this contribution, the conclusion of the original metallurgical root cause analysis (RCA), namely that the subject piping failed by transgranular chloride-induced stress corrosion cracking (Cl-SCC), could be verified and is indeed correct. The metallurgical root cause of the small bore piping (SBP) failure is chloride-induced SCC. The morphology of the cracking is very distinct and is clearly consistent with transgranular Cl-SCC. A material change to the nickel-base material Alloy 625, already considered by the client, since this alloy is believed to be immune to chloride-induced SCC, would be a good, even though expensive solution. It should be emphasized that there are no metallic materials completely resistant to SCC. If the environment is harsh enough, except for some titanium alloys, i. e., if the source of the chloride ions cannot be eliminated, which is likely the case here, a regular inspection and replacement of these SBP systems might have to be considered. It should further be emphasized that a chloride concentration below 50 ppm is by no means any guarantee for the avoidance of SCC, since chlorides can concentrate in crevices, corrosion pits and such, i. e., the local concentration is what matters, not the local.
{"title":"Metallurgical failure investigation of small bore piping (SBP) in a diesel hydrotreating unit (DHT) of an oil refinery","authors":"E. Cagliyan, B. Fischer, M. Giller, A. Neidel","doi":"10.1515/pm-2024-0046","DOIUrl":"https://doi.org/10.1515/pm-2024-0046","url":null,"abstract":"\u0000 Hydrocarbon leaks were repeatedly found in the client’s refinery. Because of the recurring nature of this failure, the operator approached the authors’ laboratory to get a second opinion on the metallurgical root cause of the failure. It was known from the customer that corrosive species, such as ammonium chloride salt precipitates, are present in the subject diesel hydrotreating unit (DHT). From the findings obtained in the investigation that is the subject of this contribution, the conclusion of the original metallurgical root cause analysis (RCA), namely that the subject piping failed by transgranular chloride-induced stress corrosion cracking (Cl-SCC), could be verified and is indeed correct. The metallurgical root cause of the small bore piping (SBP) failure is chloride-induced SCC. The morphology of the cracking is very distinct and is clearly consistent with transgranular Cl-SCC. A material change to the nickel-base material Alloy 625, already considered by the client, since this alloy is believed to be immune to chloride-induced SCC, would be a good, even though expensive solution. It should be emphasized that there are no metallic materials completely resistant to SCC. If the environment is harsh enough, except for some titanium alloys, i. e., if the source of the chloride ions cannot be eliminated, which is likely the case here, a regular inspection and replacement of these SBP systems might have to be considered. It should further be emphasized that a chloride concentration below 50 ppm is by no means any guarantee for the avoidance of SCC, since chlorides can concentrate in crevices, corrosion pits and such, i. e., the local concentration is what matters, not the local.","PeriodicalId":508095,"journal":{"name":"Practical Metallography","volume":"10 24","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141846964","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}
ASM International, an organization like DGM, has more than 15,000 members worldwide. The society was founded in 1913 as the Steel Treaters Club in Detroit. Their headquarters have been in the Cleveland, Ohio, area since 1920. ASM International has 6 Affiliate Societies including the International Metallographic Society. In 1952 the need for a focused effort in education in Material Science was recognized and the ASM Materials Education Foundation (ASM Foundation) was established. Their mission is as follows: develop and deploy materials science content and hands-on, minds-on instructional strategies to inspire, engage, and empower future generations to create STEM (Science, Technology, Engineering, Mathematics) solutions for 21st century challenges. The ASM Foundation has developed a multiprong approach to fulfil this mission and to draw young people to the field of materials science. Materials Camps for Students Teacher Education and Empowerment Mini Camps During Conferences Expansion of Camps to Europe, India and Beyond In addition, the ASM Foundation awards scholarships to undergraduate and community college students in materials science.
{"title":"Attracting a new generation to materials science","authors":"F. Hogue, M. Schleicher","doi":"10.1515/pm-2024-0049","DOIUrl":"https://doi.org/10.1515/pm-2024-0049","url":null,"abstract":"\u0000 ASM International, an organization like DGM, has more than 15,000 members worldwide. The society was founded in 1913 as the Steel Treaters Club in Detroit. Their headquarters have been in the Cleveland, Ohio, area since 1920. ASM International has 6 Affiliate Societies including the International Metallographic Society.\u0000 In 1952 the need for a focused effort in education in Material Science was recognized and the ASM Materials Education Foundation (ASM Foundation) was established. Their mission is as follows: develop and deploy materials science content and hands-on, minds-on instructional strategies to inspire, engage, and empower future generations to create STEM (Science, Technology, Engineering, Mathematics) solutions for 21st century challenges.\u0000 The ASM Foundation has developed a multiprong approach to fulfil this mission and to draw young people to the field of materials science.\u0000 \u0000 \u0000 \u0000 Materials Camps for Students\u0000 \u0000 \u0000 Teacher Education and Empowerment\u0000 \u0000 \u0000 Mini Camps During Conferences\u0000 \u0000 \u0000 Expansion of Camps to Europe, India and Beyond\u0000 \u0000 \u0000 \u0000 In addition, the ASM Foundation awards scholarships to undergraduate and community college students in materials science.","PeriodicalId":508095,"journal":{"name":"Practical Metallography","volume":"10 14","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141846970","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}
Bonded magnets are composite materials consisting of polymer matrix and magnetic powders, prepared by rapid solidification processes from Nd-Fe-B alloys. They are synthesised by the compounding process on a twin-screw extruder, whereby, the finished products of complex shapes can be made from bonded magnets using injection moulding or 3D printing by fused deposition modelling method (FDM). The main advantages of 3D printing are the possibility to produce parts with complex geometries that are not possible with traditional manufacturing techniques and low-cost production of small batches. The aim of the research work was to identify the optimum processing parameters, which would give 3D printed bonded magnets characteristics similar to those produced by injection moulding. The characterization of the microstructure of bonded magnets was made on cryo-fractured, conventionally mechanically prepared and ion beam polished samples. The microstructures of bonded magnets were analysed by stereo, optical and scanning electron microscopy. Additionally, the influence of the 3D printing parameters on the magnetic properties has been examined. The results of the research work have shown that desired magnetic properties of 3D printed bonded magnets can be obtained by optimizing the thickness of the printed layer, printing speed and flowrate. In addition, it was revealed that selection of the materialographic preparation method plays a crucial step for correct microstructural characterization. Namely, the impropriate sample preparation results in artifacts that are mostly misinterpreted as microstructural defects (pores, cracks, non-adherent layers, etc.) accidently caused during 3d printing.
粘结磁铁是由聚合物基体和磁粉组成的复合材料，由钕铁硼合金通过快速凝固工艺制备而成。它们是通过双螺杆挤压机上的复合工艺合成的，因此可以使用注塑成型或通过熔融沉积建模法（FDM）进行三维打印，将粘结磁体制成形状复杂的成品。三维打印的主要优点是可以生产出传统制造技术无法制造的复杂几何形状的零件，而且小批量生产成本低。研究工作的目的是确定最佳加工参数，使三维打印的粘结磁体具有与注塑成型生产的磁体相似的特性。对低温断裂、传统机械制备和离子束抛光样品进行了粘结磁体微观结构的表征。通过立体显微镜、光学显微镜和扫描电子显微镜对粘结磁体的微观结构进行了分析。此外，还研究了三维打印参数对磁性能的影响。研究结果表明，通过优化打印层的厚度、打印速度和流速，可以获得所需的三维打印粘合磁体的磁性能。此外，研究还发现，材料制备方法的选择是正确表征微观结构的关键步骤。也就是说，不适当的样品制备会导致伪影，而这些伪影大多被误解为 3d 打印过程中意外造成的微观结构缺陷（气孔、裂缝、非附着层等）。
{"title":"Characterization of microstructure and magnetic properties of 3D printed bonded magnets made by fused deposition modeling","authors":"M. Brunčko, A. Kneissl, L. Gorše, I. Anžel","doi":"10.1515/pm-2024-0013","DOIUrl":"https://doi.org/10.1515/pm-2024-0013","url":null,"abstract":"\u0000 Bonded magnets are composite materials consisting of polymer matrix and magnetic powders, prepared by rapid solidification processes from Nd-Fe-B alloys. They are synthesised by the compounding process on a twin-screw extruder, whereby, the finished products of complex shapes can be made from bonded magnets using injection moulding or 3D printing by fused deposition modelling method (FDM). The main advantages of 3D printing are the possibility to produce parts with complex geometries that are not possible with traditional manufacturing techniques and low-cost production of small batches.\u0000 The aim of the research work was to identify the optimum processing parameters, which would give 3D printed bonded magnets characteristics similar to those produced by injection moulding. The characterization of the microstructure of bonded magnets was made on cryo-fractured, conventionally mechanically prepared and ion beam polished samples. The microstructures of bonded magnets were analysed by stereo, optical and scanning electron microscopy. Additionally, the influence of the 3D printing parameters on the magnetic properties has been examined.\u0000 The results of the research work have shown that desired magnetic properties of 3D printed bonded magnets can be obtained by optimizing the thickness of the printed layer, printing speed and flowrate. In addition, it was revealed that selection of the materialographic preparation method plays a crucial step for correct microstructural characterization. Namely, the impropriate sample preparation results in artifacts that are mostly misinterpreted as microstructural defects (pores, cracks, non-adherent layers, etc.) accidently caused during 3d printing.","PeriodicalId":508095,"journal":{"name":"Practical Metallography","volume":"4 2","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-02-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139958314","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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