In this research, Split-Hopkinson pressure bar tests were performed on samples made from the quenched and tempered steel 42CrMo4 in four different heat-treatment conditions. These samples were ...subjected to four different pressures and five different temperatures while deforming the samples at strain rates in the range of 103 s−1. Stress-strain curves and the strain rate were computed from the measured signals. The polished cross-sections of the samples were analyzed before and after testing by means of SEM, EBSD, nanoindentation, and microhardness testing. A variety of deformation characteristics were identified and correlated with the pre-test and post-test microstructure. This work focusses on the influence of the microstructure on deformation and provides a detailed understanding on the deformation of the 42CrMo4 steel over a wide range of parameter values.
Powder bed fusion‐laser beam/metal (PBF‐LB/M) additive manufacturing provides a high potential to overcome the poor machinability of nickel‐free high interstitial alloy austenitic (HIA) steels. ...Therefore, this study focuses on the PBF‐LB/M processability of HIA X40MnCrMoN21‐18‐2 and the effect of postprocessing on microstructure and chemical homogeneity. Samples are fabricated on a laboratory and industrial PBF‐LB/M machine and subsequently postprocessed by conventional solution annealing or hot isostatic pressing (HIP). The influence of the processing steps on the microstructure and on the chemical composition is evaluated by scanning electron microscopy, X‐ray diffraction, transmission electron microscopy, atom probe tomography, and electron backscatter diffraction. The commercially available HIA powder exerts good processability, both by optimized and predefined PBF‐LB/M parameters. Loss of Mn and N is detected after PBF‐LB/M processing. Chemical homogenization but no further change in composition occurs during postprocessing. The as‐built microstructure shows segregation of elements (N, Mo, Cr, Mn) in intercellular spaces. A thermodynamic calculation confirms that N approaches a para‐equilibrium state in the PBF‐LB/M as‐built condition, while C does not. Porosity can be reduced by thermomechanical posttreatment with HIP. At the same time, HIP partially recrystallizes the microstructure, while (Mn + Cr)2SiO4 type oxides delay recovery and recrystallization of the microstructure.
High interstitial C + N alloyed Cr–Mn is an ideal alloy for additive manufacturing (AM) due to its high strength combined with high ductility and freedom from Ni. The distribution of C + N in the heterogeneous AM microstructure plays a deceptive role and is being investigated in a study of the processing route.
Metal matrix composites (MMC) are often applied to tool surfaces to increase resistance to wear and tear. However, some matrix and particle materials such as Ni, Co, WC or TiC are expensive and ...partly classified as critical elements. With respect to tribo-mechanical properties, Fe-alloys reinforced with oxide particles are promising compound materials to produce wear-resistant MMC with low-cost and readily available materials. However, thus far the technical application of such MMCs is limited due to poor wettability of the oxides by Fe-base melts and an associated weak bonding between the oxide particles and the metal matrix phases. In this work two novel production techniques (namely pre-metallization and active sintering) are introduced, which improve the wettability and interfacial reactions between both materials and therefore enable supersolidus liquid-phase sintering (SLPS) of the MMC. For the first technique the oxide particles are pre-metallized by depositing a thin film of TiN on the surfaces. The second technique is called active sintering. For this technique the alloy design is adapted from active brazing, so that wettability of the oxide particles by the alloy-melt is increased. The resulting effects of these techniques are investigated using wetting and sintering experiments, and are analyzed with respect to the developed microstructures and interfacial reactions between the oxide particles and the metallic phases.
High interstitial austenitic stainless CrMn steels are characterised by significantly increased work hardening ability and strength compared with conventional CrNi austenites, yet maintaining very ...high ductility and toughness. The machining of high interstitial CrMnCN steels is challenging in terms of process stability and economic efficiency. In this context, unfavourable chip forms, high thermomechanical loads and the superposition of different wear mechanisms in particular lead to challenges in turning operations. In the following article, different lubricant strategies are analysed for machining of CrMnN and CrMnCN austenitic stainless steels regarding chip form, mechanical tool loads and wear. Furthermore, the workpiece properties are considered with regard to surface roughness and microstructural changes.
High interstitial austenitic stainless CrMn steels are characterised by significantly increased work hardening ability and strength compared with conventional CrNi austenites, yet maintaining very ...high ductility and toughness. The machining of high interstitial CrMnCN steels is challenging in terms of process stability and economic efficiency. In this context, unfavourable chip forms, high thermomechanical loads and the superposition of different wear mechanisms in particular lead to challenges in turning operations. In the following article, different lubricant strategies are analysed for machining of CrMnN and CrMnCN austenitic stainless steels regarding chip form, mechanical tool loads and wear. Furthermore, the workpiece properties are considered with regard to surface roughness and microstructural changes. Keywords High-strength materials; stainless austenitic steels; cooling lubricants; corrosion resistance; Interstitials; work hardening; turning Nichtrostende, austenitische CrMn-Stahle zeichnen sich durch ein deutlich hoheres Kaltverfestigungsvermogen und sowie eine gesteigerte Festigkeit im Vergleich zu konventionellen CrNi-Austeniten aus, wobei sie eine sehr hohe Duktilitat und Zahigkeit aufweisen. Die Zerspanung von CrMnCN-Stahlen gestaltet sich in Bezug auf Prozessstabilitat und Wirtschaftlichkeit dabei als sehr herausfordernd. In diesem Zusammenhang fuhren insbesondere ungunstige Spanformen, hohe thermomechanische Belastungen und die Uberlagerung verschiedener Verschleissmechanismen zu Herausforderungen bei der Drehbearbeitung. Nachfolgend werden zwei unterschiedliche Schmierstoffstrategien fur die Zerspanung von austenitischen CrMnN--und CrMnCNEdelstahlen hinsichtlich Spanform, mechanischer Werkzeugbelastung und Verschleiss analysiert. Daruber hinaus werden die Werkstuckeigenschaften im Hinblick auf Oberflachenrauheit und Gefugeveranderungen betrachtet. Schlusselworter Hochfeste Werkstoffe; Nichtrostender, austenitischer Stahl; Kuhlschmierstoffe; Korrosionsbestandigkeit; Interstitielle Elemente; Kaltverfestigung; Drehbearbeitung
During machining operations, complex engagement situations between the tool and workpiece lead to varying amplitudes and directions of cutting forces. Correlations between material properties, ...process parameters and resulting forces have to be analyzed to ensure the predictability of machining processes. To model the material removal, a detailed analysis of the material behavior during the engagement is needed. In this work, a geometric physically-based simulation system is extended to take the material behavior into account for improving the prediction accuracy of process forces. A detailed analysis of the low-alloyed steel 42CrMo4 and validation experiments are presented.
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