Replacement of Nitrided 33CrMoV Steel with ESR Hot Work Tool Steels for Motorsport Applications: Microstructural and Fatigue Characterization

Ceschini

Morri

et al. 2023

Metals

Self Cite

The AlSi10Mg alloy produced by laser-based powder bed fusion (L-PBF) is widely used to produce high-value-added structural parts subjected to cyclic mechanical loads at high temperatures. The paper aims to widen the knowledge of the room- and high-temperature (200 °C) fatigue behavior of the L-PBF AlSi10Mg alloy by analyzing the fully reversed rotating bending test results on mechanically polished specimens. Two heat-treated conditions are analyzed: T5 (direct artificial aging: 4 h at 160 °C) and novel T6R (rapid solution: 10 min at 510 °C, artificial aging: 6 h at 160 °C). The study highlights that (i) the T6R alloy is characterized by higher fatigue strength at room (108 MPa) and high temperatures (92 MPa) than the T5 alloy (92 and 78 MPa, respectively); (ii) thermal exposure at 200 °C up to 17 h does not introduce macroscopical microstructural variation; (iii) fracture surfaces of the room- and high-temperature-tested specimens show comparable crack initiation, mostly from sub-superficial gas and keyhole pores, and failure propagation mechanisms. In conclusion, the L-PBF AlSi10Mg alloy offers good cyclic mechanical performances under various operating conditions, especially for the T6R alloy, and could be considered for structural components operating at temperatures up to 200 °C.

Section: Microstructural and Mechanical Characterizationmentioning

confidence: 81%

Room- and High-Temperature Fatigue Strength of the T5 and Rapid T6 Heat-Treated AlSi10Mg Alloy Produced by Laser-Based Powder Bed Fusion

Ceschini

Morri

et al. 2023

Metals

Self Cite

“…The relative density was calculated using the reference value of 7.85 g/cm 3 , measured on the ESR produced counterpart of the steel, investigated in ref. 11 Microstructural analyses were performed on cross-sections extracted in the transverse direction respect to the specimen axis. Note that, as clarified in Figure 1C, the sections extracted from 90 specimens are parallel to the x-y plane of LPBF laser scanning/building plate, while the ones extracted from 0 specimens are normal to the x-y plane (parallel to x-z/y-z planes).…”

Section: Microstructural Characterizationmentioning

confidence: 99%

“…Hence, they are generally produced via special processes such as electro‐slag remelting (ESR), vacuum‐arc remelting, or powder metallurgy (PM). Due to these characteristics, tool steels are also suitable for the manufacturing of critical mechanical components requiring high tensile and fatigue strength, stiffness, hardness, and wear resistance, such as engine camshaft and crankshaft, in replacement of nitriding steels 11 …”

Section: Introductionmentioning

confidence: 99%

Effect of heat treatment and defects on the tensile behavior of a hot work tool steel manufactured by laser powder bed fusion

Fatigue Fract Eng Mat Struct

Berto

Vullum

et al. 2023

Self Cite

Microstructure and tensile properties of a hot work tool steel manufactured via laser powder bed fusion (LPBF) were investigated. Specimens were built under two different orientations and subjected to two quenching and tempering heat treatments, featuring different austenitizing and tempering temperatures and the eventual presence of a sub-zero step. Microstructural analyses revealed a homogeneous tempered martensite structure after both heat treatments, with the only distinction of a higher alloying segregation at a sub micrometric scale length in samples subjected to the highest tempering temperatures. Hardness and tensile tests indicated a negligible effect of building orientation on mechanical properties, but a significant influence of heat treatment parameters. The treatment featuring the lower tempering temperatures and the sub-zero step resulted in higher hardness, tensile strength, and elongation, attributed to a lower martensite tempering and alloying segregation. Tensile fracture occurred via crack initiation and unstable propagation from large LPBF defects in all the investigated conditions.defects, heat treatment, laser powder bed fusion, mechanical properties, tool steel Highlights• Microstructure and tensile properties of a tool steel produced via LPBF were studied.• Tensile failure was initiated from large defects due to the LPBF process.• No effect of building orientation on microstructure and tensile properties was observed.• The treatment with the lowest tempering temperatures induced the highest properties.

“…Their in‐service performance mainly depends on hardness, toughness, wear, and fatigue resistance 1–5 . Fatigue strength and duration, in particular, are also key factors for their possible application in critical automotive components, such as engine camshafts and crankshafts, typically subjected to cyclic stress conditions 6 . The experimental assessment of fatigue strength requires statistical methods for test planning and analysis of results, such as the staircase method , 7 due to the scatter of fatigue data.…”

Section: Introductionmentioning

confidence: 99%

“…[1][2][3][4][5] Fatigue strength and duration, in particular, are also key factors for their possible application in critical automotive components, such as engine camshafts and crankshafts, typically subjected to cyclic stress conditions. 6 The experimental assessment of fatigue strength requires statistical methods for test planning and analysis of results, such as the staircase method, 7 due to the scatter of fatigue data. Due to the great number of required tests, fatigue strength evaluation is a time-consuming as well as costly operation.…”

Section: Introductionmentioning

confidence: 99%

Development and validation of a probabilistic model for notch fatigue strength prediction of tool steels based on surface defects

Fatigue Fract Eng Mat Struct

Morri

Ceschini

2021

Self Cite

A new model for the high cycle notch fatigue strength prediction of tool steels subjected to axial loading is proposed, based on previous literatures studies and experimental tests carried out on six different tool steels, including rotating bending fatigue tests on notched specimens, fractographic analyses, hardness, residual stress, and roughness measurements. The novelty is the assumption that surface defects are the main cause of notch fatigue failures of such steels. A probabilistic approach was implemented by modeling size distributions of defects, resulting in the prediction of normal distributions of fatigue strength. Like to other previous models, the effect of steel hardness, surface residual stress, notch severity, and specimen size was also taken into account. Model calibration and validation were performed using the data collected by the experimental activity. Model behavior was investigated by performing a sensitivity analysis, aiming to verify the response to variations of the considered input variables. Prediction errors of only 1.3% (on average) and 3.1% (maximum) resulted from the comparison between model-predicted and experimental notch fatigue strength.