Mechanical Properties and Corrosion Behaviour of 316l Stainless Steel Honeycomb Cellular Cores Manufactured by Selective Laser Melting

Sebastian Marian Zaharia, Camil Lancea, Lucia Antoneta Chicos, Mihai Alin Pop, Giampaolo Caputo, Emanuele Serra
2018 Transactions of FAMENA  
Selective laser technology is an additive technology that can allow for the manufacture of cellular structures using different types of metallic powder with complex applications in industries such as aerospace, automotive and medical implant industries. This paper presents the effect of climate and mechanical stresses on some honeycomb cellular cores, used in sandwich structures made of 316L stainless steel powder by applying the selective laser melting technology. The honeycomb cellular cores
more » ... ave undergone the microhardness testing and the resulting variation obtained from the analyzed samples was 225 ± 15 HV 0.3 . The compressive strength and the modulus of elasticity of the cellular structures were determined for flatwise and edgewise compressive stresses. Also, the cellular structures were subjected to accelerated corrosion tests in order to determine their mean life in application use conditions similar to those near seas and oceans. Also, a microstructural evaluation of salt deposits was carried out on the cellular structures subjected to accelerated corrosion tests using a salt spray test chamber. Mechanical Properties and Corrosion Behaviour of M.A. Pop, G. Caputo, E. Serra 316L Stainless Steel Honeycomb Cellular Cores Manufactured by Selective Laser Melting compressive and shear stresses. Between two shells the following core structures can be inserted: wood, honeycomb structure (paper, aluminium alloys, titanium and copper alloys, nickel alloys, iron alloys, fiber glass, carbon fibers, kevlar) and expanded foam [2] . The most frequently used metal cores are honeycomb core structures. They are cellular structures that are used in particular in the production of airplane floors, leading and trailing edges in wings, fuselage components, and helicopter rotor blades. Special attention is given to the environmental protection; for this purpose, the land, sea and air vehicles must be more efficient in terms of fuel consumption and take the so-called "lightweight syndrome" into account. This syndrome refers to obtaining lighter sandwich structures which reduce the weight of various components while increasing their performances. Light metal cellular structures have high strength, a relatively low weight and good performances related to: energy absorption and thermal and acoustic insulation. One modern method of manufacturing cellular structures used in sandwich structures is the additive technology. By using the additive technology the three-dimensional models of complex shapes can be achieved starting from digital three-dimensional parts by adding successive layers of material in a few hours, with minimal intervention of the human factor [3] . The main advantages of the additive manufacturing technologies are: reduction in cost of the new product; the application of these technologies allows for the experimentation with constructive solutions for the designed technological equipment, its validation or improvement; carrying out tests on models produced by the additive manufacturing technology [4] . The main types of additive manufacturing technologies are [5]: stereolithography (SLA); fused deposition modelling (FDM); selective laser sintering (SLS); selective laser melting (SLM); electronic beam melting (EBM); laminated object manufacturing (LOM). In the framework of this study the laser melting technology will be used to obtain multilayer cellular structures by consolidating some successive layers of powder type material and by using a laser in order to melt and solidify the required geometry starting from a three-dimensional model. The SLM technology allows for the manufacture of cellular structures or components using a wide range of materials: pure titanium [6], titanium alloy [7, 8, 9] , cobalt-chrome [10, 11] , stainless steel [12, 13] and aluminum alloy [14, 15, 16] . Recent studies on cellular structures manufactured by the SLM technology can be divided into the following main areas of interest: optimizing the laser settings (power and exposure time) in order to obtain different structures and the effect of production parameters in stainless steel [17] ; manufacture of implants using cellular structures [18, 19] , manufacture and optimization of cellular structures geometry produced by the SLM technology, starting from the unit cell geometries, sizes and strut cell diameters [20, 21, 22, 23] , testing the cellular structures obtained by the SLM technology [9, 14, 15, 22, 23] , finite element analysis of cellular structures [17, 24] . A great part of the studies on cellular structures focus on the manufacture and then the determination of the failure and deformation mechanisms followed by various microscopic analyses. The behaviour testing analysis of cellular structures manufactured by using the additive technology is a challenge for specialists in the field. Tests are currently performed to determine the mechanical properties of cellular structures under various stresses (compressive, bending and tensile), that are obtained by the SLM technologies. Mines et al. [25] studied the impact behaviour of sandwich panels with carbon fibre reinforced polymer (CFRP) face sheets and micro lattice core (body centered cubic /BCC/) of the Ti6Al4V and the 316L stainless steel manufactured by the SLM technology. Another study was undertaken by Riemer et al. [26] who investigated the high-cycle fatigue performance of 316L steel
doi:10.21278/tof.41402 fatcat:a5rgh5udkrfzfkvrlmatxyoeqy