Abstract
The selective laser melting (SLM) method has a great potential for fabricating injection mold with complex structure. However, the microstructure and performance of the SLM molds show significantly different from those manufactured by traditional technologies. In this study, the microstructure, hardness and especially corrosion behavior of the samples fabricated by SLM and casting were investigated. The XRD results exhibit that the γ-Fe phase is only obtained in the SLM parts, and the α-Fe peak slightly moves to low diffraction angle compared with casting counterparts. Due to the rapid cooling rate, the SLM samples have fine cellular microstructures while the casting ones have coarse grains with obvious elements segregation. Besides, the SLM samples show anisotropy, hardness of side view and top view are 48.73 and 50.31 HRC respectively, which are 20% higher than that of casting ones. Corrosion results show that the SLM samples have the better anti-corrosion resistance (in a 6% FeCl3 solution for 48 h) but the deeper corrosion pits than casting ones. Finally, the performance of the SLM molds could meet the requirement of injecting production. Moreover, the molds especially present a significant decrease (20%) of cooling time and increases of cooling uniformity due to the customized conformal cooling channels.
Highlights
Injection molds were widely used for mass production of thermoplastic parts with a high production efficiency [1]
Different from the casting S136, the powder and as-selective laser melting (SLM) S136 includes austenite γ-Fe phase, which is similar with the results from previous observations during SLM of AISI 420 [16, 27]
Based on the XRD patterns, the volume fractions of the alloy phases were estimated by the reference intensity ratio method (RIR) [28] and listed in Samples α-Fe phase (%)
Summary
Injection molds were widely used for mass production of thermoplastic parts with a high production efficiency [1]. The quality of injection production is related to the mold steel materials [2] and the structure [3, 4]. Cooling channels in molds greatly affect the productivity, product deformation and die life [5, 6]. Conventional straight-line channels cause a heterogeneous heat dissipation and cooling due to the inconsistency between channels and mold cavities. The emerging conformal cooling channels that conform to mold cavities can bring into a steady and homogeneous heat transfer from the cavity surfaces to the coolant, which improves directly the product quality [9]. It is difficult to fabricate molds with
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