Abstract
Due to a good combination of high hardness, wear resistance, toughness, resistance to high operating temperatures, and fairly low material cost, AISI H13 tool steel is commonly used in the manufacture of injection molds. Additive manufacturing (AM) such as selective laser melting (SLM), due to the layer-wise nature of the process, offers substantial geometric design freedom in comparison with conventional subtractive manufacturing methods, thereby enabling a construction of complex near-net shape parts with internal cavities like conformal cooling channels. The quality of SLM-manufactured parts mainly depends on the part geometry, build orientation and scanning strategy, and processing parameters. In this study, samples of H13 tool steel with a size of 10 × 10 × 15 mm3 were SLM-manufactured using a laser power of 100, 200, and 300 W; scanning speed of 200, 400, 600, 800, 1000, and 1200 mm/s; and hatch spacing of 80 and 120 µm. A constant layer thickness of 40 µm, 67° scanning rotation between subsequent layers, and a stripe scanning strategy were maintained during the process. The samples were built considering a preheating of 200 °C. The relative density, surface roughness, crack formation, microstructure, and hardness were evaluated. The relative density is shown to increase with increasing the volumetric energy density up to a value of about 60 J/mm3 and then no significant increase can be pointed out; the maximum relative density of 99.7% was obtained. A preheating of 200 °C generally aids to increase the relative density and eliminate the crack formation. The microstructure of built samples shows fine equiaxed cellular-dendritic structure with martensite and some retained austenite. The microhardness of the as-built samples was found to vary from 650 to 689 HV 0.2, which is comparable to a conventionally produced H13 tool steel.
Highlights
Owing to the layer-wise nature of the process, additive manufacturing (AM) technology allows with a high degree of accuracy for the manufacture of complex-shape geometries, quite difficult or impossible to obtain using conventional material-removal processes, opening significant opportunities up for the design of novel geometries and complex internal structures
The fabrication of a component by AM technology does aid to eliminate the need for molds and dies or any additional fixtures, coolants and cutting tools, with minimal finishing operations, resulting in a significant reduction in lead-time, material wastes, energy, and costs
Results and Discussionprocess to build the batch of samples took a continuous 22 h to finish; The manufacturing as can be observed
Summary
Owing to the layer-wise nature of the process, additive manufacturing (AM) technology allows with a high degree of accuracy for the manufacture of complex-shape geometries, quite difficult or impossible to obtain using conventional material-removal processes, opening significant opportunities up for the design of novel geometries and complex internal structures. To build a layer of predefined geometry, the powder is melted by a focused heat source provided by an electron beam, laser, plasma or electric welding arc, etc. The fabrication of a component by AM technology does aid to eliminate the need for molds and dies or any additional fixtures, coolants and cutting tools, with minimal finishing operations, resulting in a significant reduction in lead-time, material wastes, energy, and costs. Materials 2019, 12, 2284 its vast advantages, AM has become a crucial alternative manufacturing technique for small quantities of components having complex geometries [1]. Of several AM processes, selective laser melting (SLM) has gained an essential role in the field of metallic materials. SLM implies that a laser beam selectively melts and fuses accumulating layers of powder
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