Preparation and mechanical properties of selective laser melted H13 steel
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, Dehong Lu1,a), Rong Zhou1, Zhenhua Li1, Jieren Guan1
1
Faculty of Materials Science and Engineering, Kunming University of Science and Technology, Kunming 650093, China Address all correspondence to this author. e-mail: [email protected]
a)
Received: 19 August 2018; accepted: 17 December 2018
Process parameters (laser power and scanning speed) for H13 steel specimens produced by selective laser melting (SLM) are optimized, and microstructural characteristics and mechanical properties are investigated. The optimum process parameters are a laser power of 170 W and a scanning speed of 400 mm/s according to the maximum relative density of 99.2%. The microstructure consists of cellular grains and columnar crystal, which are composed of lath martensite and retained austenite, and there are no carbides or other second-phase particles present. The size of cellular grains is 1 lm. Compared with the common processed (forged and heat-treated) H13, SLM H13 has similar microhardness (561 HV) and tensile strength (1909 MPa) values. However, the elongation (12.4%) is a factor of ∼3 times higher and the impact energy (14.4 J) of the SLM specimen is somewhat lower. The relationship between the microstructure and mechanical properties is discussed. Fine grains and no second-phase precipitation determine the strength and plasticity of SLM samples.
Introduction H13 steel is a typical medium-carbon, hot-work tool steel that possesses superior thermal strength, red hardness, and resistance to thermal fatigue, and it has been widely applied to make various dies for the hot extrusion, forging, and highpressure casting of aluminum and magnesium alloys [1, 2]. However, the making of dies using traditional manufacturing methods is a limited and time-consuming process. In particular, the fabrication of a molding cooling system is directly related to the service life of the die. Using traditional manufacturing technology, one can only design conventional drilled cooling channels, which restrict the channel consistency and the shapes of mold cavities. These deficiencies lead to uneven heat dissipation, an increase in the cooling cycle, large internal stress, and a shortened mold service life [3]. Selective laser melting (SLM), which is also called 3D printing, is a disruptive technology in which one can produce very complex geometries that are not available via traditional manufacturing methods [4]. It is used across multiple industries, including the aerospace, biomedical, automotive [5], and mold industries [6]. Three-dimensional printing allows cooling channels to match the cavity shape, thereby countering the limitation of conventional drilled cooling channels [3].
ª Materials Research Society 2019
At the same time, SLM can achieve complex castings for singleor small-batch production and it enables the development of new products in the mold-making industry. Consequently, the use of the SLM of H13 die steel as the focus of study has attracted increasing attention. The performance of the SLM of H13 steel is an important standard fo
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