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Research Papers

Local Microstructure and Hardness Variation After Pulsed Laser Micromelting on S7 Tool Steel

[+] Author and Article Information
Justin D. Morrow

Mem. ASME
Department of Mechanical Engineering,
University of Wisconsin-Madison,
1513 University Avenue,
Madison, WI 53706
e-mail: jdmorrow@wisc.edu

Frank E. Pfefferkorn

Mem. ASME
Department of Mechanical Engineering,
University of Wisconsin-Madison,
1513 University Avenue,
Madison, WI 53706
e-mail: frank.pfefferkorn@wisc.edu

Contributed by the Manufacturing Engineering Division of ASME for publication in the JOURNAL OF MICRO- AND NANO-MANUFACTURING. Manuscript received November 9, 2015; final manuscript received June 13, 2016; published online July 11, 2016. Assoc. Editor: Stefan Dimov.

J. Micro Nano-Manuf 4(3), 031006 (Jul 11, 2016) (10 pages) Paper No: JMNM-15-1078; doi: 10.1115/1.4033924 History: Received November 09, 2015; Revised June 13, 2016

Laser surface melting is being increasingly used as a method of surface polishing steels and other alloys, but understanding the effect of this process on the microstructure and properties is still incomplete. This work experimentally explores several basic questions about how the surface microstructure and properties of S7 tool steel change during a pulsed laser micromelting (PLμM) process. Evaluations of the microstructure and hardness suggest that diffusion-controlled processes such as melt homogenization and surface back-tempering are relevant during rapid microscale laser melting and that the laser parameters and process planning contribute to determining the final surface hardness. The results also suggest that some influence can be exerted over the final hardness obtained from laser surface melting by changing the processing parameters.

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Copyright © 2016 by ASME
Topics: Lasers , Melting , Tool steel
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References

Lakhkar, R. S. , Shin, Y. C. , and Krane, M. J. M. , 2008, “ Predictive Modeling of Multi-Track Laser Hardening of AISI 4140 Steel,” Mater. Sci. Eng.: A, 480(1–2), pp. 209–217. [CrossRef]
Chiang, K.-A. , and Chen, Y.-C. , 2005, “ Laser Surface Hardening of H13 Steel in the Melt Case,” Mater. Lett., 59(14–15), pp. 1919–1923. [CrossRef]
Ganeev, R. A. , 2002, “ Low-Power Laser Hardening of Steels,” J. Mater. Process. Technol., 121(2–3), pp. 414–419. [CrossRef]
Wang, Q. , Morrow, J. D. , Ma, C. , Duffie, N. A. , and Pfefferkorn, F. E. , 2015, “ Surface Prediction Model for Thermocapillary Regime Pulsed Laser Micro Polishing of Metals,” J. Manuf. Processes, 20(1), pp. 340–348. [CrossRef]
Pfefferkorn, F. E. , Duffie, N. A. , Morrow, J. D. , and Wang, Q. , 2014, “ Effect of Beam Diameter on Pulsed Laser Polishing of S7 Tool Steel,” CIRP Ann.-Manuf. Technol., 63(1), pp. 237–240. [CrossRef]
Perry, T. L. , Werschmoeller, D. , Li, X. , Pfefferkorn, F. E. , and Duffie, N. A. , 2009, “ Pulsed Laser Polishing of Micro-Milled Ti6Al4V Samples,” J. Manuf. Processes, 11(2), pp. 74–81. [CrossRef]
Vadali, M. , Ma, C. , Duffie, N. A. , Li, X. , and Pfefferkorn, F. E. , 2012, “ Pulsed Laser Micro Polishing: Surface Prediction Model,” J. Manuf. Processes, 14(3), pp. 307–315. [CrossRef]
Hafiz, A. M. K. , Bordatchev, E. V. , and Tutunea-Fatan, R. O. , 2012, “ Influence of Overlap Between the Laser Beam Tracks on Surface Quality in Laser Polishing of AISI H13 Tool Steel,” J. Manuf. Processes, 14(4), pp. 425–434. [CrossRef]
Avilés, R. , Albizuri, J. , Lamikiz, A. , Ukar, E. , and Avilés, A. , 2011, “ Influence of Laser Polishing on the High Cycle Fatigue Strength of Medium Carbon AISI 1045 Steel,” Int. J. Fatigue, 33(11), pp. 1477–1489. [CrossRef]
Baumgart, P. , Krajnovich, D. J. , Nguyen, T. A. , and Tam, A. C. , 1995, “ A New Laser Texturing Technique for High Performance Magnetic Disk Drives,” IEEE Trans. Magn., 31(6), pp. 2946–2951. [CrossRef]
Etsion, I. , 2005, “ State of the Art in Laser Surface Texturing,” ASME J. Tribol., 127(1), pp. 248–253. [CrossRef]
Ashby, M. F. , and Easterling, K. E. , 1984, “ The Transformation Hardening of Steel Surfaces by Laser Beams—I. Hypo-Eutectoid Steels,” Acta Metall., 32(11), pp. 1935–1948. [CrossRef]
Skvarenina, S. , and Shin, Y. C. , 2006, “ Predictive Modeling and Experimental Results for Laser Hardening of AISI 1536 Steel With Complex Geometric Features by a High Power Diode Laser,” Surf. Coat. Technol., 201(6), pp. 2256–2269. [CrossRef]
Bhadeshia, H. , and Honeycombe, R. , 2011, Steels: Microstructure and Properties: Microstructure and Properties, Butterworth-Heinemann, Oxford, UK.
Zhang, Z. , Delagnes, D. , and Bernhart, G. , 2004, “ Microstructure Evolution of Hot-Work Tool Steels During Tempering and Definition of a Kinetic Law Based on Hardness Measurements,” Mater. Sci. Eng.: A, 380(1–2), pp. 222–230. [CrossRef]
Giorleo, L. , Previtali, B. , and Semeraro, Q. , 2011, “ Modelling of Back Tempering in Laser Hardening,” Int. J. Adv. Manuf. Technol., 54(9), pp. 969–977. [CrossRef]
Hollomon, J. H. , and Jaffe, L. D. , 1945, “ Time-Temperature Relations in Tempering Steel,” AIME, 162, pp. 223–249.
Preußner, J. , Oeser, S. , Pfeiffer, W. , Temmler, A. , and Willenborg, E. , 2014, “ Microstructure and Residual Stresses of Laser Remelted Surfaces of a Hot Work Tool Steel,” Int. J. Mater. Res., 105(4), pp. 328–336. [CrossRef]
Benyounis, K. Y. , Fakron, O. M. , and Abboud, J. H. , 2009, “ Rapid Solidification of M2 High-Speed Steel by Laser Melting,” Mater. Des., 30(3), pp. 674–678. [CrossRef]
Morrow, J. D. , Wang, Q. , Duffie, N. A. , and Pfefferkorn, F. E. , 2014, “ Effects of Pulsed Laser Micro Polishing on Microstructure and Mechanical Properties of S7 Tool Steel,” 9th International Conference on Micromanufacturing (ICOMM 2014), Singapore, March 25–28.
Pfefferkorn, F. E. , Duffie, N. A. , Li, X. , Vadali, M. , and Ma, C. , 2013, “ Improving Surface Finish in Pulsed Laser Micro Polishing Using Thermocapillary Flow,” CIRP Ann.-Manuf. Technol., 62(1), pp. 203–206. [CrossRef]
Ma, C. , Vadali, M. , Li, X. , Duffie, N. A. , and Pfefferkorn, F. E. , 2014, “ Analytical and Experimental Investigation of Thermocapillary Flow in Pulsed Laser Micropolishing,” ASME J. Micro Nano-Manuf., 2(2), p. 021010. [CrossRef]
Arias, J. , Cabeza, M. , Castro, G. , Feijoo, I. , Merino, P. , and Pena, G. , 2010, “ Microstructural Characterization of Laser Surface Melted AISI M2 Tool Steel,” J. Microsc., 239(3), pp. 184–193. [CrossRef] [PubMed]
Temmler, A. , Graichen, K. , and Donath, J. , 2010, “ Laser Polishing in Medical Engineering,” Laser Tech. J., 7(2), pp. 53–57. [CrossRef]
Bordatchev, E. V. , Hafiz, A. M. K. , and Tutunea-Fatan, O. R. , 2014, “ Performance of Laser Polishing in Finishing of Metallic Surfaces,” Int. J. Adv. Manuf. Technol., 73(1–4), pp. 35–52. [CrossRef]
Perry, T. L. , Werschmoeller, D. , Duffie, N. A. , Li, X. , and Pfefferkorn, F. E. , 2009, “ Examination of Selective Pulsed Laser Micropolishing on Microfabricated Nickel Samples Using Spatial Frequency Analysis,” ASME J. Manuf. Sci. Eng., 131(2), p. 021002. [CrossRef]
Morrow, J. D. , Wang, Q. , and Pfefferkorn, F. E. , 2015, “ Microstructure of S7 Tool Steel After Pulsed Laser Micro Polishing,” 4M/ICOMM 2015 Conference, Milan, Italy, March 31–April 2.
Oliver, W. C. , and Pharr, G. M. , 1992, “ An Improved Technique for Determining Hardness and Elastic Modulus Using Load and Displacement Sensing Indentation Experiments,” J. Mater. Res., 7(6), pp. 1564–1583. [CrossRef]
Ohmori, Y. , and Tamura, I. , 1992, “ Epsilon Carbide Precipitation During Tempering of Plain Carbon Martensite,” Metall. Trans. A, 23(10), pp. 2737–2751. [CrossRef]
Nagakura, S. , Suzuki, T. , and Kusunoki, M. , 1981, “ Structure of the Precipitated Particles at the Third Stage of Tempering of Martensitic Iron-Carbon Steel Studied by High Resolution Electron Microscopy,” Trans. Jpn. Inst. Met., 22(10), pp. 699–709. [CrossRef]
Caron, R. N. , and Krauss, G. , 1972, “ The Tempering of Fe-C Lath Martensite,” Metall. Trans., 3(9), pp. 2381–2389. [CrossRef]
Kąc, S. , and Kusiński, J. , 2003, “ SEM and TEM Microstructural Investigation of High-Speed Tool Steel After Laser Melting,” Mater. Chem. Phys., 81(2–3), pp. 510–512. [CrossRef]
Yasavol, N. , Abdollah-Zadeh, A. , Ganjali, M. , and Alidokht, S. A. , 2013, “ Microstructure and Mechanical Behavior of Pulsed Laser Surface Melted AISI D2 Cold Work Tool Steel,” Appl. Surf. Sci., 265, pp. 653–662. [CrossRef]

Figures

Grahic Jump Location
Fig. 2

(a) A typical load versus displacement (P versus h) curve, (b) SEM micrograph of a single indent, and (c) diagram of the hardness (H) mapping method on a mock dataset where each data point represents an individual indent

Grahic Jump Location
Fig. 1

Diagrams of (a) unidirectional and zig-zag scan paths and (b) the laser spot overlapping typical in creating PLμM lines and areas

Grahic Jump Location
Fig. 3

Scanning electron micrographs of (a) a PLμM spot, (b) line, and (c) area. The left side image shows the resulting surface topography and the right side shows the underlying microstructure. Inset images show (d) the edge of a laser spot and ((e) and (f)) carbide formation in an overlap region of a PLμM area scan.

Grahic Jump Location
Fig. 4

The hardness as a function of indentation depth plots for the (a) laser spots, (b) laser lines, and (c) laser areas. Indents that had a depth exceeding the calibrated range (i.e., hc > 230 nm) are included in gray. Each figure has an inset histogram showing the distribution: The measured hardness of the laser lines and area showed a unimodal distribution while the laser spots showed a trimodal distribution in the hardness, as shown in the inset histogram. SEM evaluation (d) of eight laser spots showed that the indentation placement on laser spots was often near the melt pool edge and occasionally missed the spots entirely.

Grahic Jump Location
Fig. 5

Secondary electron micrographs of etched S7 steel: (a) as-received (annealed) and (b) furnace hardened

Grahic Jump Location
Fig. 6

Microstructure and hardness of condition showing the correlation between local back-tempering and hardness change: (a) A, (b) B then A, (c) A then B, and (d) B. The tempered overlap regions are indicated with arrows in (b). Hardness ranges (mean ± 1 standard deviation) of the furnace hardened and annealed surfaces are also included as gray boxes for reference.

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