Microstructure and Electrochemical and Tribological Properties of Inconel718 Alloy Formed by Selective Laser Melting

The Inconel718 alloy was prepared by laser selective melting (SLM) technique with Inconel718 alloy powder prepared by aerosol method as raw materials. The microstructure and properties of the alloy were studied and compared with those of the forged alloy. The results show that the microstructure of the SLM formed alloy perpendicular to the forming direction presented obvious banded melting channels, and that parallel to the forming direction showed the interface structure of fish-scale molten pool; the grains were columnar crystals passing through the boundary of molten pool. The microhardness of the SLM formed alloy parallel to the forming direction (346 HV) was slightly greater than that perpendicular to the forming direction (324 HV). Compared with those of the forged alloy, the SLM formed alloy exhibited a larger impedance curve radius in 3.5wt%NaCl solution, higher free-corrosion potential and passivation potential, and lower free-corrosion current density by two orders of magnitude, indicating better corrosion resistance. The friction coefficient of the SLM formed alloy was 0.5-0.8, and the wear rate was 5.4×10^-5-14.3×10^-5 mm^-3·N^-1·m^-1 under the load of 3-10 N, which were all lower than those of the forged alloy.