Abstract It is demonstrated that high speed steels are suitable for manufacturing of heat resistant rolling element bearings especially for applications in aero engines. A detailed analysis of heat treating processes and metallurgical evaluation shows how the properties of these steels grades can be adjusted to meet the specific requirements for engine bearings. Based on results from rig testing it is shown how variations in heat treating parameters can influence the rolling contact fatigue performance. The role of carbides, a typical constituent of high speed steels, on bearing applications is discussed in detail. The high level of heat resistance of high speed steels allows a nitriding in addition to the conventional heat treatment. By nitriding an increase in hardness close to the surface can be achieved which can make bearings more robust against indentation of hard particles. ◼
{"title":"Heat Treatment and Properties of High-Temperature Steels for Rolling Bearings","authors":"O. Beer","doi":"10.1515/htm-2021-0001","DOIUrl":"https://doi.org/10.1515/htm-2021-0001","url":null,"abstract":"Abstract It is demonstrated that high speed steels are suitable for manufacturing of heat resistant rolling element bearings especially for applications in aero engines. A detailed analysis of heat treating processes and metallurgical evaluation shows how the properties of these steels grades can be adjusted to meet the specific requirements for engine bearings. Based on results from rig testing it is shown how variations in heat treating parameters can influence the rolling contact fatigue performance. The role of carbides, a typical constituent of high speed steels, on bearing applications is discussed in detail. The high level of heat resistance of high speed steels allows a nitriding in addition to the conventional heat treatment. By nitriding an increase in hardness close to the surface can be achieved which can make bearings more robust against indentation of hard particles. ◼","PeriodicalId":44294,"journal":{"name":"HTM-Journal of Heat Treatment and Materials","volume":"171 1","pages":"155 - 171"},"PeriodicalIF":0.6,"publicationDate":"2021-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82262596","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}
S. Geroldinger, R. Oro Calderon, C. Gierl-Mayer, H. Danninger
Abstract In powder metallurgy (PM), there are several ways of introducing alloying elements into a PM material in order to adjust a certain alloying element content. Each alloying route has its advantages and disadvantages. Master alloys (MA), powders with a high content of typically several alloying elements, can be added in small amounts to a base powder, especially to introduce oxygen sensitive elements such as Cr, Mn, and Si. In addition, the master alloy can be designed in such a way that a liquid phase is formed intermediately during the sintering process to improve the distribution of alloying elements in the material and to accelerate homogenization. In this study, such master alloys were combined with pre-alloyed base powders to form hybrid alloyed mixtures with the aim of improving the material‘s sinter hardenability. The hybrid alloys were compared with mixtures of master alloy and plain Fe as reference material. The sinter hardenability of all materials was determined by generating CCT diagrams recorded with 13 different cooling rates. These were verified by metallographic cross-sections of specimens treated at common cooling rates of 3 and 1.5 K/s and subsequent hardness measurements of the microhardness (HV 0.1) of the microstructural constituents and the apparent hardness (HV 30). ◼
{"title":"Sinter Hardening PM Steels Prepared through Hybrid Alloying","authors":"S. Geroldinger, R. Oro Calderon, C. Gierl-Mayer, H. Danninger","doi":"10.1515/htm-2020-0007","DOIUrl":"https://doi.org/10.1515/htm-2020-0007","url":null,"abstract":"Abstract In powder metallurgy (PM), there are several ways of introducing alloying elements into a PM material in order to adjust a certain alloying element content. Each alloying route has its advantages and disadvantages. Master alloys (MA), powders with a high content of typically several alloying elements, can be added in small amounts to a base powder, especially to introduce oxygen sensitive elements such as Cr, Mn, and Si. In addition, the master alloy can be designed in such a way that a liquid phase is formed intermediately during the sintering process to improve the distribution of alloying elements in the material and to accelerate homogenization. In this study, such master alloys were combined with pre-alloyed base powders to form hybrid alloyed mixtures with the aim of improving the material‘s sinter hardenability. The hybrid alloys were compared with mixtures of master alloy and plain Fe as reference material. The sinter hardenability of all materials was determined by generating CCT diagrams recorded with 13 different cooling rates. These were verified by metallographic cross-sections of specimens treated at common cooling rates of 3 and 1.5 K/s and subsequent hardness measurements of the microhardness (HV 0.1) of the microstructural constituents and the apparent hardness (HV 30). ◼","PeriodicalId":44294,"journal":{"name":"HTM-Journal of Heat Treatment and Materials","volume":"7 1","pages":"105 - 119"},"PeriodicalIF":0.6,"publicationDate":"2021-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87347155","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 Segregation is an unavoidable phenomenon in continuous or ingot casting of steel for thermodynamic reasons. If costly processes that explicitly reduce segregation are not carried out, the segregations remain until the final product. Therefore, an understanding of the development and effects of segregation along the entire process chain is necessary. The focus in this publication is on the treatment of segregations in low alloy steels. First, the characterisation of segregation is presented. An overview of the formation and development of segregations during primary shaping and forming processes is given. The focus is on segregation-related effects during heat treatment with regard to inhomogeneous microstructure and negative heat treatment results such as distortion or hardening cracks. In a short outlook, the influence of segregation on the component behaviour is described. ◼
{"title":"Segregations in Steels during Heat Treatment – A Consideration along the Process Chain","authors":"M. Hunkel","doi":"10.1515/htm-2020-0006","DOIUrl":"https://doi.org/10.1515/htm-2020-0006","url":null,"abstract":"Abstract Segregation is an unavoidable phenomenon in continuous or ingot casting of steel for thermodynamic reasons. If costly processes that explicitly reduce segregation are not carried out, the segregations remain until the final product. Therefore, an understanding of the development and effects of segregation along the entire process chain is necessary. The focus in this publication is on the treatment of segregations in low alloy steels. First, the characterisation of segregation is presented. An overview of the formation and development of segregations during primary shaping and forming processes is given. The focus is on segregation-related effects during heat treatment with regard to inhomogeneous microstructure and negative heat treatment results such as distortion or hardening cracks. In a short outlook, the influence of segregation on the component behaviour is described. ◼","PeriodicalId":44294,"journal":{"name":"HTM-Journal of Heat Treatment and Materials","volume":"53 1","pages":"79 - 104"},"PeriodicalIF":0.6,"publicationDate":"2021-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85068188","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 manufacturing process of grinding generally leads to a thermo-mechanical influence on the surface integrity. In addition to the intended development of residual compressive stresses due to the finishing process, disturbances in the grinding process can lead to negative effects such as tensile residual stresses, tempering and even rehardening zones and significantly reduce the component lifetime. In industrial applications, the analysis of Barkhausen noise is becoming increasingly important for the detection of this unwanted thermo-mechanically influenced surface integrity. The non-destructive method reacts sensitively to changes in, for example, the residual stress state as well as the hardness. In addition, other material-, process- and metrology-related influences are described in literature. The investigations presented in this paper deal with the influence of different material states (case-hardening depth, surface carbon content and alloy composition) on the signals of the Barkhausen noise as a function of the surface integrity. It is shown that the signal level is significantly influenced by the material condition and thus individual limit values must be used for evaluation of the surface integrity. ◼
{"title":"Influence of the Material State of Ground, Case-Hardened Steels on the Barkhausen Noise Depending on the Surface Integrity*","authors":"D. Sackmann, J. Heinzel, B. Karpuschewski","doi":"10.1515/htm-2020-0001","DOIUrl":"https://doi.org/10.1515/htm-2020-0001","url":null,"abstract":"Abstract The manufacturing process of grinding generally leads to a thermo-mechanical influence on the surface integrity. In addition to the intended development of residual compressive stresses due to the finishing process, disturbances in the grinding process can lead to negative effects such as tensile residual stresses, tempering and even rehardening zones and significantly reduce the component lifetime. In industrial applications, the analysis of Barkhausen noise is becoming increasingly important for the detection of this unwanted thermo-mechanically influenced surface integrity. The non-destructive method reacts sensitively to changes in, for example, the residual stress state as well as the hardness. In addition, other material-, process- and metrology-related influences are described in literature. The investigations presented in this paper deal with the influence of different material states (case-hardening depth, surface carbon content and alloy composition) on the signals of the Barkhausen noise as a function of the surface integrity. It is shown that the signal level is significantly influenced by the material condition and thus individual limit values must be used for evaluation of the surface integrity. ◼","PeriodicalId":44294,"journal":{"name":"HTM-Journal of Heat Treatment and Materials","volume":"22 1","pages":"5 - 18"},"PeriodicalIF":0.6,"publicationDate":"2021-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84782070","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}
J. Damon, H. Surm, P. Saddei, S. Dietrich, V. Schulze
Abstract Case hardening processes such as carbonitriding can be used to improve the performance of powder metallurgical structural components. Due to the amount of carbon and nitrogen introduced, it is possible to adjust the hardness and residual stress of the surface layer. Due to their porosity, powder metallurgical components show a significantly increased diffusivity and therefore increased demands on the process control. In order to be able to make a quantitative statement about the effects of diffusivity as a function of porosity, common densities of 6.9 g/cm3, 7.2 g/cm3and 7.35 g/cm3for PM-steel are examined in a total of ten process sequences. By means of simulative approaches, the resulting element depth profiles can be calculated and the surface layer condition can be predicted by a subsequent heat treatment simulation. In a two-part work, the mass transport during carbonitriding is investigated in the first part and the resulting surface layer conditions after heat treatment in the second part. By considering different process combinations and porosities, model approaches of volume and pore diffusion can be formulated and quantitative element depth profiles can be predicted and validated depending on the process parameters. ◼
{"title":"Experimental and Numerical Investigation of the Surface Layer Conditions after Carbonitriding of Powder Metallurgical Steels. Part 1: Diffusion in Components of Graded Porosity","authors":"J. Damon, H. Surm, P. Saddei, S. Dietrich, V. Schulze","doi":"10.1515/htm-2020-0003","DOIUrl":"https://doi.org/10.1515/htm-2020-0003","url":null,"abstract":"Abstract Case hardening processes such as carbonitriding can be used to improve the performance of powder metallurgical structural components. Due to the amount of carbon and nitrogen introduced, it is possible to adjust the hardness and residual stress of the surface layer. Due to their porosity, powder metallurgical components show a significantly increased diffusivity and therefore increased demands on the process control. In order to be able to make a quantitative statement about the effects of diffusivity as a function of porosity, common densities of 6.9 g/cm3, 7.2 g/cm3and 7.35 g/cm3for PM-steel are examined in a total of ten process sequences. By means of simulative approaches, the resulting element depth profiles can be calculated and the surface layer condition can be predicted by a subsequent heat treatment simulation. In a two-part work, the mass transport during carbonitriding is investigated in the first part and the resulting surface layer conditions after heat treatment in the second part. By considering different process combinations and porosities, model approaches of volume and pore diffusion can be formulated and quantitative element depth profiles can be predicted and validated depending on the process parameters. ◼","PeriodicalId":44294,"journal":{"name":"HTM-Journal of Heat Treatment and Materials","volume":"109 1","pages":"36 - 57"},"PeriodicalIF":0.6,"publicationDate":"2021-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74500807","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 Globalization and international supply chains constantly challenge gear- and steel manufacturers. In the case of large gear units in particular, expensive alloy contents have a direct impact on the material price. Steels with lower alloy contents and therefore cheaper steels are therefore becoming the focus of attention in order to further improve competitiveness. This article therefore compares two materials with different alloying elements and contents and thus different hardenability behaviour. For this purpose, extensive material characterizations as well as pulsator tests were carried out on case-hardened large gears. The aim of these tests was to determine the tooth root load-bearing capacity of the two material variants. Finally, the results are compared, discussed and recommendations for industrial application are derived, taking into account the hardenability of large gears. ◼
{"title":"Suitable Material Selection for Large Size Cylindrical Gears*","authors":"D. Fuchs, C. Güntner, T. Tobie, K. Stahl","doi":"10.1515/htm-2020-0002","DOIUrl":"https://doi.org/10.1515/htm-2020-0002","url":null,"abstract":"Abstract Globalization and international supply chains constantly challenge gear- and steel manufacturers. In the case of large gear units in particular, expensive alloy contents have a direct impact on the material price. Steels with lower alloy contents and therefore cheaper steels are therefore becoming the focus of attention in order to further improve competitiveness. This article therefore compares two materials with different alloying elements and contents and thus different hardenability behaviour. For this purpose, extensive material characterizations as well as pulsator tests were carried out on case-hardened large gears. The aim of these tests was to determine the tooth root load-bearing capacity of the two material variants. Finally, the results are compared, discussed and recommendations for industrial application are derived, taking into account the hardenability of large gears. ◼","PeriodicalId":44294,"journal":{"name":"HTM-Journal of Heat Treatment and Materials","volume":"74 1","pages":"19 - 35"},"PeriodicalIF":0.6,"publicationDate":"2021-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74270414","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 mechanism of plasma nitriding include the formation of various active species generating nitrogen atoms reacting with the metal. Which species prevail in supplying nitrogen depends on nitriding conditions as well as the nature of the treated metal. Plasma nitriding of low-density powder metal (PM) products results in a formation of the layers whose thicknesses may depend on the gas pressure used for the process. Higher pressure can cause locally deeper penetration of the surface by active nitrogen species formed from ammonia compounds generated by the plasma. While a low processing pressure reduces this effect significantly. The formation mechanism of a locally thicker layer relies on the presence of open porosities in the surface as they can be penetrated by the ammonia species generated by the plasma. The same porosities cannot be penetrated by the ions of nitrogen formed at the same time since their mean free life is much shorter than that of ammonia species. ◼
{"title":"Plasma Nitriding Mechanisms of Low-Density Sintered Metal Products","authors":"E. Rolinski, M. Woods","doi":"10.1515/htm-2020-0004","DOIUrl":"https://doi.org/10.1515/htm-2020-0004","url":null,"abstract":"Abstract The mechanism of plasma nitriding include the formation of various active species generating nitrogen atoms reacting with the metal. Which species prevail in supplying nitrogen depends on nitriding conditions as well as the nature of the treated metal. Plasma nitriding of low-density powder metal (PM) products results in a formation of the layers whose thicknesses may depend on the gas pressure used for the process. Higher pressure can cause locally deeper penetration of the surface by active nitrogen species formed from ammonia compounds generated by the plasma. While a low processing pressure reduces this effect significantly. The formation mechanism of a locally thicker layer relies on the presence of open porosities in the surface as they can be penetrated by the ammonia species generated by the plasma. The same porosities cannot be penetrated by the ions of nitrogen formed at the same time since their mean free life is much shorter than that of ammonia species. ◼","PeriodicalId":44294,"journal":{"name":"HTM-Journal of Heat Treatment and Materials","volume":"5 1","pages":"58 - 63"},"PeriodicalIF":0.6,"publicationDate":"2021-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75021283","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":"HTM Praxis","authors":"","doi":"10.1515/htm-2020-1008","DOIUrl":"https://doi.org/10.1515/htm-2020-1008","url":null,"abstract":"","PeriodicalId":44294,"journal":{"name":"HTM-Journal of Heat Treatment and Materials","volume":"52 1","pages":""},"PeriodicalIF":0.6,"publicationDate":"2021-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80706790","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 Twin-roll casting (TRC) is a set up applied to manufacture sheets of aluminium alloys. In spite of huge potential, extreme centerline segregation emerges during casting. This segregation limits the range of alloys suitable for commercial applications. To enhance the quality of the TRC strips, another innovation– the melt-conditioning twin-roll casting (MCTRC) – has been used. Cold rolling followed by homogenization heat treatment of the MCTRC strip results in more uniform solute distribution across the thickness of the strip, leading to strips of higher quality as compared to the conventional TRC strip.
{"title":"Mechanical Deformation and Heat Treatment Processing of Twin Roll Cast and Melt Processed Al-5 wt.% Mg Alloy Strips","authors":"B. Dhindaw, N. Gupta, N. Barekar, A. Mandal","doi":"10.3139/105.110427","DOIUrl":"https://doi.org/10.3139/105.110427","url":null,"abstract":"Abstract Twin-roll casting (TRC) is a set up applied to manufacture sheets of aluminium alloys. In spite of huge potential, extreme centerline segregation emerges during casting. This segregation limits the range of alloys suitable for commercial applications. To enhance the quality of the TRC strips, another innovation– the melt-conditioning twin-roll casting (MCTRC) – has been used. Cold rolling followed by homogenization heat treatment of the MCTRC strip results in more uniform solute distribution across the thickness of the strip, leading to strips of higher quality as compared to the conventional TRC strip.","PeriodicalId":44294,"journal":{"name":"HTM-Journal of Heat Treatment and Materials","volume":"1 1","pages":"433 - 441"},"PeriodicalIF":0.6,"publicationDate":"2020-12-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74899515","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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