Selective Laser Melting of TiB2-Reinforced S136 Die Steels
(2.Faculty of Engineering, China University of Geosciences, Wuhan, Hubei, China 430074)
【Abstract】The selective laser melting (SLM) technology is used to process the TiB2/S136 composites and the effect of laser energy density η on the densities, microstructures and mechanical properties of SLM-processed specimens is investigated. X-ray diffraction instrument, field emission scanning electron microscopy and transmission electron microscopy are used to study the phase compositions, surface morphologies and microstructures of specimens. The results show that when η is low, the powders are not fully molten and thus a large amount of residual pores are formed. However, when η is too high, the micro-cracks are formed in the specimens because of thermal stress. When η is 66.7 J/mm3, the specimens have less surface defects, and their densities are up to 97.3%. There exist fine and uniformly-distributed equiaxed grains. As for these specimens, the average microhardness is up to 742.4 HV0.1, and the average friction coefficient and wear rate are 0.559 3 and 0.272 × 10−4mm3·N−1·m−1, respectively, indicating an excellent abrasion resistance performance. The tensile strength is 1 051.3 MPa and the elongation is 5.84%, indicating a relatively good plasticity. Above all, the optimal η for the SLM-processed TiB2/S136 composites is 66.7 J/mm3, and if η is too high or too low, the densities and mechanical properties of TiB2/S136 composites would be seriously affected. This study provides a useful theoretical basis and process guidance for SLM-processed high-performance die steels.
【Keywords】 laser optics; selective laser melting; energy density; TiB2/S136 composites; microstructure; mechanical properties;
(Translated by LIU T)
 Zhao X, Wei Q S, Liu Y, et al. 激光选区熔化技术成形S136模具钢研究 [C].∥The 15th national academic conference on special processing: paper collection of the 15th national academic conference on special processing, 2013: 295–299 (in Chinese).
 Yadroitsev I, Gusarov A, Yadroitsava I, et al. Single track formation in selective laser melting of metal powders [J]. Journal of Materials Processing Technology, 2010, 210 (12): 1624–1631.
 Kruth J P, Froyen L, van Vaerenbergh J, et al. Selective laser melting of iron-based powder [J]. Journal of Materials Processing Technology, 2004, 149 (1/2/3): 616–622.
 Huang W D, Lin X. Research progress in laser solid forming of high performance metallic component [J]. Materials China, 2010, 29 (6): 12–27 (in Chinese).
 Wang H M. Research progress on laser surface modifications of metallic materials and laser rapid forming of high performance metallic components [J]. Acta Aeronautica et Astronautica Sinica, 2002, 23 (5): 473–478 (in Chinese).
 Zhang T B, Hu R, Zhong H, et al. Microstructure of directionally solidified Gd5Si4 by laser zone remelting [J]. Rare Metal Materials and Engineering, 2012, 41 (10): 1837–1841 (in Chinese).
 Chen J, Zhao X M, Yang H O, et al. Study on mechanical properties of superalloy by laser rapid forming [J]. Rare Metal Materials and Engineering, 2008, 37 (9): 1664–1668 (in Chinese).
 AlMangour B, Grzesiak D, Yang J M. Nanocrystalline TiC-reinforced H13 steel matrix nanocomposites fabricated by selective laser melting [J]. Materials & Design, 2016, 96: 150–161.
 AlMangour B, Grzesiak D, Yang J M. Selective laser melting of TiB2/H13steel nanocomposites: influence of hot isostatic pressing post-treatment [J]. Journal of Materials Processing Technology, 2017, 244: 344–353.
 Wen S F, Wu X L, Zhou Y, et al. Microstructure and property of S136 mould steel fabricated by selective laser melting [J]. Journal of Huazhong University of Science and Technology (Nature Science Edition) , 2018, 46 (2): 51–55 (in Chinese).
 Zhang G Q, Gu D D. Selective laser melting of TiC solid solution strengthened tungsten matrix composites [J]. Rare Metal Materials and Engineering, 2015, 44 (4): 1017–1023 (in Chinese).
 Enneti R K, Morgan R, Atre S V. Effect of process parameters on the selective laser melting (SLM) of tungsten [J]. International Journal of Refractory Metals and Hard Materials, 2018, 71: 315–319.
 Koutiri I, Pessard E, Peyre P, et al. Influence of SLM process parameters on the surface finish, porosity rate and fatigue behavior of as-built Inconel 625 parts [J]. Journal of Materials Processing Technology, 2018, 255: 536–546.
 Liverani E, Toschi S, Ceschini L, et al. Effect of selective laser melting (SLM) process parameters on microstructure and mechanical properties of 316L austenitic stainless steel [J]. Journal of Materials Processing Technology, 2017, 249: 255–263.
 Gu D D, Hagedorn Y C, Meiners W, et al. Nanocrystalline TiC reinforced Ti matrix bulk-form nanocomposites by selective laser melting (SLM): densification, growth mechanism and wear behavior [J]. Composites Science and Technology, 2011, 71 (13): 1612–1620.
 Zhao X. Fundamental Research on the Microstructure and Properties Evolution of Tool Steels Fabricated by Selective Laser Melting. Wuhan: Huazhong University of Science and Technology, 2016 (in Chinese).
 Li R D, Liu J H, Shi Y S, et al. Balling behavior of stainless steel and nickel powder during selective laser melting process [J]. The International Journal of Advanced Manufacturing Technology, 2012, 59 (9/10/11/12): 1025–1035.
 Qiu C L, Panwisawas C, Ward M, et al. On the role of melt flow into the surface structure and porosity development during selective laser melting [J]. Acta Materialia, 2015, 96: 72–79.
 Iida T, Guthrie R I L. The physical properties of liquid metals [M]. Oxford: Clarendon Press, 1993: 255–265.
 Zhou S F, Zeng X Y, Hu Q W, et al. Analysis of crack behavior for Ni-based WC composite coatings by laser cladding and crack-free realization [J]. Applied Surface Science, 2008, 255 (5): 1646–1653.
 Kadolkar P B, Watkins T R, de Hosson J T M, et al. State of residual stress in laser-deposited ceramic composite coatings on aluminum alloys [J]. Acta Materialia, 2007, 55 (4): 1203–1214.
 Sulima I, Klimczyk P, Malczewski P. Effect of TiB2 particles on the tribological properties of stainless steel matrix composites [J]. Acta Metallurgica Sinica (English Letters) , 2014, 27 (1): 12–18.
 Li H, Wang M, Zhou P X, et al. Effects of surface topography and wettability on surface heterogeneous nucleation [J]. Foundry Technology, 2012, 33 (6): 641–644 (in Chinese).
 Xu S C, Zhou L X, Zhang Z C, et al. Effect of heat treatment on austenite grain size of SAE4320 steel [J]. Heat Treatment of Metals, 2014, 39 (11): 111–113 (in Chinese).
 Gu D D, Wang H Q, Dai D H, et al. Rapid fabrication of Al-based bulk-form nanocomposites with novel reinforcement and enhanced performance by selective laser melting [J]. Scripta Materialia, 2015, 96: 25–28.
 Niu H J, Chang I T H. Selective laser sintering of gas and water atomized high speed steel powders [J]. Scripta Materialia, 1999, 41 (1): 25–30.
 Gu D D, Meiners W, Wissenbach K, et al. Laser additive manufacturing of metallic components: materials, processes and mechanisms [J]. International Materials Reviews, 2012, 57 (3): 133–164.
 Simonelli M, Tse Y Y, Tuck C. Effect of the build orientation on the mechanical properties and fracture modes of SLM Ti-6Al-4V [J]. Materials Science and Engineering: A, 2014, 616: 1–11.
 Wang S, Cheng X, Tian X J, et al. Effect of TiCaddition on microstructures and properties of MC carbide reinforced Inconel625 composites by laser additive manufacturing [J]. Chinese Journal of Lasers, 2018, 45 (6): 0602002 (in Chinese).
 Wen S F, Hu H, Zhou Y, et al. Enhanced hardness and wear property of S136 mould steel with nano-TiB2 composites fabricated by selective laser melting method [J]. Applied Surface Science, 2018, 457: 11–20.