Additive Manufacturing of Cobalt‐Based Dental Alloys: Analysis of Microstructure and Physicomechanical Properties

Abstract

The limitations of investment casting of cobalt-based alloys are claimed to be less problematic with significant improvements in metal additive manufacturing by selective laser melting (SLM). Despite these advantages, the metallic devices are likely to display mechanical anisotropy in relation to build orientations, which could consequently affect their performance “in vivo.” In addition, there is inconclusive evidence concerning the requisite composition and postprocessing steps (e.g., heat treatment to relieve stress) that must be completed prior to using the devices. In the current paper, we evaluate the microstructure of ternary cobalt-chromium-molybdenum (Co-Cr-Mo) and cobalt-chromium-tungsten (Co-Cr-W) alloys built with direct metal printing and LaserCUSING SLM systems, respectively, at 0°, 30°, 60°, and 90° inclinations (Φ) in as-built (AB) and heat-treated (HT) conditions. The study also examines the tensile properties (Young’s modulus, E; yield strength, RP0.2; elongation at failure, At; and ultimate tensile strength, Rm), relative density (RD), and microhardness (HV5) and macrohardness (HV20) as relevant physicomechanical properties of the alloys. Data obtained indicate improved tensile properties and HV values after a short and cost-effective heat-treatment cycle of Co-Cr-Mo alloys; however, the process did not homogenize the microstructure of the alloy. Annealing heat treatment of Co-Cr-W led to significant isotropic characteristics with increased E and At (except for Φ = 90°) in contrast to decreased RP0.2, Rm, and HV values, compared to the AB form. Similarly, the interlaced weld-bead structures in AB Co-Cr-W were removed during heat treatment, which led to a complete recrystallization of the microstructure. Both alloys exhibited defect-free microstructures with RD exceeding 99.5%.

Mechanical Properties of Dental Alloys According to Manufacturing Process

“…After removing the wax pattern by heating the mold, when the cast body reaches the casting temperature, the molten metal is injected into the space, which is also called a wax loss method or an investment method. Casting technology is a traditional dental prosthesis manufacturing method that has been used for a long time, but since all processes are performed by hand, it takes a long time, and incomplete casting may occur; as a result, different outcomes may be obtained depending on the skill of the technician [ 1 , 2 , 3 , 4 , 5 , 6 , 7 ].…”

“…However, in recent years, as the manufacturing technology of dental prosthesis is further developed and digital technology, such as CAD (computer-aided design)/CAM (computer-aided manufacturing), is widely introduced in the dental field, many changes have occurred in the manufacturing method of dental prosthesis. In particular, an oral scanner is used in the process of taking an impression, and CAD/CAM equipment has already been commercialized and used in the process of making a model and a wax pattern [ 6 , 7 , 8 , 9 ].…”

“…The milling process solves the problem of porosity, which is a casting defect, in that the CAM process shortens the manufacturing time of the prosthesis and improves the precision of the framework. The CAM process uses a milling machine or computer numerical control (CNC) machining to cut the material with a machine, and all steps are controlled by a computer program [ 6 , 7 , 8 ]. However, the milling method consumes a lot of raw materials for the metal block and, in the case of using a high-strength metal material, it has the disadvantage of frequent wear of the milling tool and restricts detailed work [ 1 , 2 , 8 , 9 ].…”

Перспективы Развития 3d-Печати

“…Металлические материалы обладают превосходными физическими свойствами и материалы могут использованы для изготовления сложных изделий от печати человеческих органов до аэрокосмических деталей. Примерами таких материалов являются алюминиевые сплавы [28], сплавы на основе титана [29], кобальта [30], никеля [31] и нержавеющей стали [32].…”

Process parameter optimization for removable partial denture frameworks manufactured by selective laser melting

“…The accuracy of 3D-printed RPD frameworks is influenced by the process parameters, including laser scanning condition, [11][12][13][14][15] hatching strategies (the scanning paths for laser melting), 16 inert gas flow in chamber, 17 support design, part orientation, 7 and the heat treatment methods after processing, 18,19 affecting the physical and mechanical properties of the prosthesis. [12][13][14][15] For example, inappropriate process parameters can induce micropores, providing crack initiation sites when mechanical stress is applied.…”