Abstract
Materials with higher wear resistance are required in various applications including cutting elements (drag bits) of soft ground tunnel boring machines (TBM) to increase the productivity and to reduce the risk for workers involved in exchange operations (dangerous hyperbolic conditions). In recent work, two types of materials were produced by combining 3D printing (selective laser melting, SLM) of cellular lattice structures and spark plasma sintering (SPS) methods. The lattices were printed from (1) 316L stainless steel with diamond and (2) Ti6Al4V with nitriding. The effect of diamond content (5%, 10%, and 20%; nickel-coated particles) and unit cell size on performance was studied. The titanium alloy lattice was nitrided to increase its hardness and wear resistance. The effect of nitriding temperature (750°C, 900°C, and 1050°C) and lattice volume fraction (6%, 15%, and 24%, vol.) was investigated, and the optimized conditions were applied. The lattices were filled with 316L and Ti6Al4V powders, respectively, and consolidated by SPS. Samples were tested with the help of laboratory impact-abrasive tribodevice. Laboratory results have shown that both reinforcing approaches are beneficial and allow improvement of wear resistance in impact-abrasive conditions with great potential for TBM or similar applications. Modelling with the help of finite element method has shown that lattice structure enables reduction of peak local stresses in scratching and impact conditions.
Highlights
Materials with higher wear resistance are required in various applications including mining, cutting, drilling, and tunnel boring machines (TBM) to increase the productivity and to reduce the risk for employees and time required for exchange operations
Effect of laser power and scanning speed on strut diameter has been thoroughly investigated, and it is in direct proportion with laser power if constant scanning speed is used [13]. e study of AlSi10Mg gyroid-type cellular lattices has confirmed that an increase in the volume fraction of lattice material leads to rising of compressive strength while the increase in unit cell size leads to lower microhardness [14]
Two types of materials were produced by combining 3D printing (SLM) of cellular lattice structures and spark plasma sintering (SPS) techniques
Summary
Stainless steel grade AISI 316L is an austenitic iron-based (with chromium, nickel, and molybdenum additions), low carbon, and the nonmagnetic alloy used for corrosion resistance and additive manufacturing applications. e powders of 316L are spherical and have good flowability that is important for feeding of 3D metal printing machine. Diamond-type cellular lattices have been printed by Realizer SLM50 machine from 316L and Ti6Al4V (Figures 2 and 3), respectively. E first type of materials was made of 316L stainless steel with a varied percentage of nickel-coated diamond particles. E reinforcement of the second materials was achieved by nitriding of Ti6Al4V lattice printed with different cell sizes. The insert prepared by traditional powder metallurgy methods and 3D-printed structure ready for filling and the following consolidation by HIP or SPS are given in Figures 5(a)–5(c), respectively. E first approach of reinforcement was realized by adding diamond particles into AISI 316L metal matrix prior to 3D printing of lattice. Diamond particles were covered by nickel coating (56 wt.%) to reduce diamond transformation
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