Microstructural and Torsional Fatigue Characteristics of Singleshot and Scan Induction Hardened 1045 and 10V45 Steels
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Scan and single-shot induction hardening were used to harden 1045 and 10V45 steels. Torsional fatigue testing found that while case hardness was higher in 10V45, 1045 exhibited greater ductility during crack propagation, leading to improved fatigue life. Scan hardening produced a finer prior austenite grain size and lower residual stresses than single-shot hardening. However, fatigue performance was similar between the two processes at 550 MPa stress amplitude, with single-shot showing 70% higher life at 650 MPa.
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Microstructural and Torsional Fatigue Characteristics of Singleshot and Scan Induction Hardened 1045 and 10V45 Steels
- 1. 1 Microstructural and Torsional Fatigue Characteristics of Single- shot and Scan Induction Hardened 1045 and 10V45 Steels Lee Rothleutner1, Jody Burke2, Dr. Chester J. Van Tyne1, and Robert Cryderman1 1Advanced Steel Processing and Products Research Center Colorado School of Mines, Golden, CO 80401 USA 2Gerdau Special Steel North America, Jackson, MI 49201 USA Additional support from Rob Goldstein of Fluxtrol Inc. as well as Rob Madeira and Jeff Elinski of Inductoheat Inc.
- 2. 2 Study Design Induction hardened shaft ... Performance ↑ Strength ↑ Fatigue life 1. High case depth 2. Favorable case microstructure 3. Favorable residual stress profile Processing • Power • Frequency • Quenchant (conc. & flow rate) • Coil design • Scan speed
- 3. 3 Study Design Scope... • Scan vs. Single-shot induction hardened – Effective case depth of 44% (~70% of area) – 1045 and 10V45 (F/P starting microstructure) Outline... 1. Case microstructure 2. Residual stresses (near surface) 3. Torsional fatigue performance (550, 600, 650 MPa stress amplitude, R=0.1)
- 4. 4 Materials – Chemistry wt pct C Mn Si Ni+Cr+Mo V Al N P S Cu DIb (mm) 1045 0.44a 0.74 0.23 0.25 0.002 0.016 0.0068 0.010 0.006 0.26 35.6 10V45 0.47a 0.82 0.28 0.24 0.080 0.007 0.0100 0.007 0.009 0.22 45.5 Minc 0.43 0.60 --- --- --- --- --- --- --- --- --- Maxc 0.50 0.90 --- --- --- --- --- 0.040 0.050 --- --- a Standard Deviation of 0.01 wt pct (n = 5) b ASTM A255-10: Standard Test Methods for Determining Hardenability of Steel c ASTM A29-12: Standard Specification for General Requirements for Steel Bars, Carbon and Alloy, Hot-Wrought Hot Rolled to 39.7 mm (1.563 in) Diameter Bar (18.8 to 1)
- 5. 5 Materials – Microstructure 1045 10V45 Transverse Characteristics 1045 10V45 Pearlite (%) 83.1 ± 2.0 86.5 ± 1.5 Pearlite ILS (nm) 225 ± 6.4 207 ± 7.1 Ferrite Grain Size (µm) 6.4 ± 0.2 3.3 ± 0.1 Ferrite Grain Circularity 0.76 ± 0.01 0.82 ± 0.01 Hardness (HV1kg) 217 ± 5 281 ± 9
- 6. 6 Materials – V(C,N) Precipitation V(C,N) diameter 4.5 ± 0.3 nm 10V45 – Proeutectoid Ferrite BF DF 𝑏 = 011 𝛼𝐹𝑒 𝑔 = 020 𝑉(𝐶,𝑁)
- 7. 7 Materials – V(C,N) Precipitation 10V45 – Pearlitic Ferrite V(C,N) diameter 3.3 ± 0.3 nm DFBF
- 9. 9 Induction Hardening Scan Single-shot Scan Single-Shot Power (kW) 72 128 Freq. (kHz) 196 31 Scan Rate (mm/s) 17.3 --- UCON A Concentration 6% 2% Flow Rate (L/min) 75 144
- 10. 10 Induction Hardening Measured at Minimum Specimen Diameter Scan Single-shot
- 11. 11 Equivalent Hardness 𝐻𝑉𝑒𝑞 = 3 𝑅3 0 𝑅 𝐻𝑉(𝑟)𝑟2 𝑑𝑟 𝑑𝑟 𝑟 𝑅 Tempered at 176 °C for 90 min after induction hardening. HVeq ∝ Torsional Strength ∝ Fatigue Life
- 12. 12 Microstructure – Scan Tempered at 176 °C for 90 min 10V45-Scan
- 13. 13 Microstructure – Single-shot 10V45-Single Tempered at 176 °C for 90 min
- 14. 14 Case Microstructure Depth from Surface Scan Single-shot 1045 10V45 1045 10V45 0.0 mm --- --- --- R 0.5 mm --- R + T R R + T 0.0 mm 0.5 mm 10V45... Higher tendency for non-martensitic transformation products both retained (R) and transformed (T) ferrite. No ghost pearlite was observed within 0.5 mm of surface in any condition. 10V45-Single 10V45-Single
- 15. 15 Case Microstructure – PAGS 1045-Scan 10V45-Single 10V45 is not significantly different from 1045 for a given processing routine.
- 16. 16 Residual Stress 10V45 is not significantly different from 1045 for a given processing routine.
- 17. 17 Residual Stress Octahedral Shear Stress 𝜎 𝐻 = ± 1 2 𝜎1 2 + 𝜎2 2 + 𝜎1 − 𝜎2 2 −𝜏 𝑥𝑦 𝑟𝑒𝑠 - 𝜎 𝑦 𝑟𝑒𝑠 -𝜎 𝑥 𝑟𝑒𝑠 -𝜃 𝜎1 -𝜎2 •= 10V45 is not significantly different from 1045 for a given processing routine. 35% 25%
- 18. 18 Torsional Fatigue Specimen 95% of Max Shear Stress Longitudinal Cross-section 15.5 mm (mm)
- 19. 19 Torsional Fatigue Crack System 𝜎 𝜏 = −𝜏 𝑥𝑦 𝑎𝑝𝑝 -45° 𝜎1 𝑎𝑝𝑝 −𝜎2 𝑎𝑝𝑝 𝜏 𝜏 𝑚𝑎𝑥 𝜏 𝑚𝑖𝑛 𝜏 𝑚 𝜏 𝑎 𝑡𝑖𝑚𝑒 I III II
- 20. 20 Torsional Fatigue – Scan 1045 10V45 650 MPa 43,100 cycles 650 MPa 46,400 cycles 1045 exhibits more ductility in case during crack propagation then 10V45.
- 21. 21 Torsional Fatigue – Scan 1045 10V45 550 MPa 122,500 cycles 550 MPa 510,000 cycles 1045 exhibits more ductility in case during crack propagation then 10V45.
- 22. 22 Torsional Fatigue – Single-shot 1045 10V45 650 MPa 128,600 cycles 650 MPa 127,100 cycles 1045 exhibits more ductility in case during crack propagation then 10V45.
- 23. 23 Torsional Fatigue – Single-shot 1045 10V45 550 MPa 240,000 cycles 550 MPa 448,000 cycles 1045 exhibits more ductility in case during crack propagation then 10V45.
- 24. 24 Torsional Fatigue (MPa) Scan Single-shot 1045 10V45 1045 10V45 650 --- --- --- 1/5 600 --- --- --- 4/5 550 3/5 3/5 2/5 4/5 𝜏 𝑎 Sub-surface Initiations Initiation location: Case hardness in 10V45 is higher then 1045 (~2 HRC). ~70%
- 25. 25 Scan vs. Single-shot Hardness Profiles: Scan ≈ Single-shot Case Non-martensitic Trans. Products: Scan < Single-shot Prior Austenite Grain Size: Scan > Single-shot (~25%) Near-Surface Residual Stress: Scan < Single-shot Fatigue Life: Scan ≈ Single-shot (at 550 MPa) Scan < Single-shot (~70% higher )𝜏 𝑎
- 26. 26 Thank you for your attention! Lee M. Rothleutner lrothleu@mines.edu
- 27. 27 Residual Stress • Incremental Hole Drilling Method – ASTM E837 – Type A strain gage rosette. – Inverted cone diamond mill. – Strain measured every 0.05 mm to 1 mm. – H-DRILL (v3.11) software • Prof. Gary Schajer (UBC) Hoop Axial Diamond Mill Micrometer Head Air Turbine Assembly Light •Vishay M-M •RS-200 X & Y Adjustment
- 28. 28 Net Stress - 𝜎 𝑦 𝑠 -𝜎𝑥 𝑠 𝜏 𝑥𝑦 𝑠 Residual Stress State Applied Stress State Net Stress State Resultant Principal Stresses 𝜎 𝜏 + −𝜏 𝑥𝑦 𝑟𝑒𝑠 - 𝜎 𝑦 𝑟𝑒𝑠 -𝜎𝑥 𝑟𝑒𝑠 -𝜃 𝜎1 -𝜎2 = 𝜏 𝑥𝑦 𝑎𝑝𝑝 𝜎 𝜏 + =𝜎 𝜏 𝜎 𝜏 = =
- 29. 29 Net Stress Maximum Reduction in Applied Stress -𝜃 𝜎1 -𝜎2 Positive throughout test. Negative throughout test. Between -30° (at min) and -45° (at max). -𝜎2 𝜎1 -𝜃 10V45 is not significantly different from 1045 for a given processing routine. (MPa) Scan Single-shot 650 -400 -560 550 -400 -560 𝝈1