scholarly journals Influence of surface morphology on the very high cycle fatigue behavior of metastable and stable austenitic Cr-Ni steels

2018 ◽  
Vol 165 ◽  
pp. 20008 ◽  
Author(s):  
Annika Boemke ◽  
Marek Smaga ◽  
Tilmann Beck
Keyword(s):  
Phase Transformation ◽  
Surface Layer ◽  
Surface Morphology ◽  
Austenitic Steel ◽  
Grain Refinement ◽  
Fatigue Testing ◽  
Testing Machine ◽  
Metastable Austenitic Steel ◽  
Steel Aisi ◽  
Cryogenic Turning

The present study investigates conventional and cryogenically turned specimens of metastable austenitic steel AISI 347 and stable austenitic steel AISI 904L in the VHCF regime. The cryogenic turning process includes cooling by CO2 snow and generates a surface layer on the specimens of metastable austenitic steel, which is characterized by a phase transformation from paramagnetic fcc - austenite to ferromagnetic bcc - martensite and grain refinement. The stable austenitic steel retains its purely austenitic structure after cryogenic turning, but also shows grain refinement in the surface layer. The specimens with different surface morphology were cyclically loaded at ambient temperature using an ultrasonic fatigue testing system developed and built at the authors’ institute. The testing machine operates at frequencies of approx. 20 kHz to achieve high numbers of load cycles within a reasonable time. To avoid self heating of the specimen, the tests were performed in pulse-pause mode. All specimens were tested with a load ratio of R = -1. During cyclic loading, the metastable austenitic steel partially transformed from paramagnetic fcc - austenite to ferromagnetic bcc - martensite, while no phase transformation could be detected in the stable austenitic steel.

Investigations on Cryogenic Turning to Achieve Surface Hardening of Metastable Austenitic Steel AISI 347

2014 ◽  
Vol 1018 ◽  
pp. 153-160 ◽  
Author(s):  
Patrick Mayer ◽  
Benjamin Kirsch ◽  
Jan C. Aurich
Keyword(s):  
Phase Transformation ◽  
Surface Layer ◽  
Surface Hardening ◽  
Cryogenic Cooling ◽  
Austenitic Steels ◽  
Phase Content ◽  
Martensite Formation ◽  
Metastable Austenitic Steel ◽  
Steel Aisi ◽  
Cryogenic Turning

Metastable austenitic steels offer the opportunity of a surface hardening during machining due to a deformation induced martensite formation, substituting downstream hardening-processes. To maintain the necessary low process and workpiece temperatures for a phase transformation from austenite to martensite, cryogenic cooling using CO2-snow was examined in this study. The influence of workpiece diameter, coolant flow rate as well as pre-cooling and pre-surface hardening on the obtainable phase content of martensite in the surface layer was investigated.

A Finite Element Approach to Calculate Temperatures Arising During Cryogenic Turning of Metastable Austenitic Steel AISI 347

2018 ◽  
Author(s):  
Steven Becker ◽  
Hendrik Hotz ◽  
Benjamin Kirsch ◽  
Jan C. Aurich ◽  
Erik v. Harbou ◽  
...  
Keyword(s):  
Austenitic Steel ◽  
Cutting Speed ◽  
Cutting Parameters ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Metastable Austenitic Steel ◽  
System A ◽  
Element Approach ◽  
Steel Aisi ◽  
Cryogenic Turning

In this paper an inverse method is presented to evaluate the inner workpiece temperature distribution during cryogenic turning of metastable austenitic steel AISI 347 utilizing a FE representation of the process. Temperature data during the experiments is provided by thermocouples and a commercial thermo-graphy system. A constant cutting speed at two varying feeds are investigated. Inverse parameter verification by aligning simulated and experimental data in a least squares sense is achieved. A heat flux from tool to workpiece as well as heat transfer coefficients for forced convection by air and by carbon dioxide as cryogenic coolant are identified for each set of cutting parameters. Rigid body rotation in the model is considered applying convective time derivatives of the temperature field. Unphysical oscillations occurring in regions of high Péclet numbers are suppressed utilizing a streamline-upwind/Petrov-Galerkin scheme.

A Finite Element Approach to Calculate Temperatures Arising During Cryogenic Turning of Metastable Austenitic Steel AISI 347

2018 ◽  
Vol 140 (10) ◽  
Author(s):  
Steven Becker ◽  
Hendrik Hotz ◽  
Benjamin Kirsch ◽  
Jan C. Aurich ◽  
Erik V. Harbou ◽  
...  
Keyword(s):  
Austenitic Steel ◽  
Cutting Speed ◽  
Cutting Parameters ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Metastable Austenitic Steel ◽  
System A ◽  
Element Approach ◽  
Steel Aisi ◽  
Cryogenic Turning

In this paper, an inverse method is presented to evaluate the inner workpiece temperature distribution during cryogenic turning of metastable austenitic steel AISI 347 utilizing a FE representation of the process. Temperature data during the experiments are provided by thermocouples and a commercial thermography system. A constant cutting speed at two varying feeds is investigated. Inverse parameter verification by aligning simulated and experimental data in a least squares sense is achieved. A heat flux from tool to workpiece as well as heat transfer coefficients for forced convection by air and by carbon dioxide as cryogenic coolant are identified for each set of cutting parameters. Rigid body rotation in the model is considered applying convective time derivatives of the temperature field. Unphysical oscillations occurring in regions of high Péclet numbers are suppressed utilizing a streamline-upwind/Petrov–Galerkin scheme.

scholarly journals Improving the surface morphology of metastable austenitic steel AISI 347 in a two-step turning process

Procedia CIRP ◽  
2018 ◽  
Vol 71 ◽  
pp. 160-165 ◽  
Author(s):  
H. Hotz ◽  
B. Kirsch ◽  
S. Becker ◽  
E. von Harbou ◽  
R. Müller ◽  
...  
Keyword(s):  
Surface Morphology ◽  
Austenitic Steel ◽  
Turning Process ◽  
Metastable Austenitic Steel ◽  
Steel Aisi

scholarly journals Surface layer hardening of metastable austenitic steel – Comparison of shot peening and cryogenic turning

2020 ◽  
Vol 9 (6) ◽  
pp. 16410-16422
Author(s):  
Hendrik Hotz ◽  
Benjamin Kirsch ◽  
Tong Zhu ◽  
Marek Smaga ◽  
Tilmann Beck ◽  
...  
Keyword(s):  
Surface Layer ◽  
Austenitic Steel ◽  
Shot Peening ◽  
Metastable Austenitic Steel ◽  
Surface Layer Hardening ◽  
Cryogenic Turning

scholarly journals Transient Finite Element Simulation of the Temperature Field during Cryogenic Turning of Metastable Austenitic Steel AISI 347

PAMM ◽  
2016 ◽  
Vol 16 (1) ◽  
pp. 303-304 ◽  
Author(s):  
Steven Becker ◽  
Patrick Mayer ◽  
Benjamin Kirsch ◽  
Jan C. Aurich ◽  
Erik v. Harbou ◽  
...  
Keyword(s):  
Finite Element ◽  
Temperature Field ◽  
Austenitic Steel ◽  
Finite Element Simulation ◽  
Metastable Austenitic Steel ◽  
Element Simulation ◽  
Steel Aisi ◽  
Cryogenic Turning

Influence of Surface Morphology on the Fatigue Behavior of Metastable Austenitic Steel

2014 ◽  
Vol 891-892 ◽  
pp. 464-469 ◽  
Author(s):  
Robert Skorupski ◽  
Marek Smaga ◽  
Dietmar Eifler
Keyword(s):  
Surface Morphology ◽  
Austenitic Steel ◽  
Fatigue Behavior ◽  
Magnetic Measurement ◽  
Fatigue Tests ◽  
X Ray ◽  
Metastable Austenitic Steel ◽  
Steel Aisi ◽  
Cutting Zone

Using a low temperature turning process with carbon dioxide cooling in the cutting zone a variation of the morphology at the specimen surfaces of the metastable austenitic steel AISI 347 was realized. In LCF and HCF fatigue tests at ambient temperature and 300 °C the influence of the surface morphology on the cyclic deformation behavior and fatigue life was investigated by the measurement of stress-strain hysteresis. An additional magnetic measurement allows the characterization of the phase transformation from paramagnetic austenite in ferromagnetic α´-martensite during the turning processes and during cyclic loading. The surface morphology was studied in detail by SEM and x-ray investigations.

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