Microstructures and Mechanical Properties of Dental Co-Cr-Mo-W Alloys Fabricated by Selective Laser Melting at Different
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WEI is with the School of Aeronautics & Astronautics, Sichuan University, Chengdu, 610065, China and also with the School of Manufacturing Science and Engineering, Sichuan University, Chengdu, 610065, China. YANAN ZHOU, QI SUN, NING LI, JIAZHEN YAN, HAOPENG LI, and WENBO LIU are with the School of Manufacturing Science and Engineering, Sichuan University. Contact e-mail: [email protected] CHONGXIANG HUANG is with the School of Aeronautics & Astronautics, Sichuan University. Manuscript submitted October 8, 2019.
METALLURGICAL AND MATERIALS TRANSACTIONS A
INTRODUCTION
CO-CR based alloys have been widely applied to various types of orthopedic implants because of their excellent mechanical properties, prominent biocompatibility, good corrosion resistance, and good wear resistance.[1–3] These alloys can be divided into two basic groups: Co-Cr-Mo alloys and Co-Cr-Mo-W alloys. Co-Cr-Mo alloys are often used to manufacture orthopedic implants, such as artificial knees, shoulders, and hips. Chromium primarily improves alloy corrosion resistance. Molybdenum affects grain refinement and matrix strengthening. Generally, Co-Cr-Mo alloys contain some carbon elements (no more than 0.35 pct), and carbide strengthening is the primary strengthening method.[4] Compared with Co-Cr-Mo alloys,
Co-Cr-Mo-W alloys containing tungsten are characterized by lower thickness in the oxide layer during the production process.[5] In addition, tungsten will decrease the coefficient of thermal expansion of alloys. The previous two points can effectively improve metal-porcelain bond strength during the porcelain fused to metal (PFM) production process, reducing the risk of the porcelain cracking.[6] Co-Cr-Mo-W alloys are ideal biomedical material for PFM crowns, removable partial dentures, and metal frames.[7] However, all previous applications required complex shapes and personalized designs, which result in challenges in manufacturing when casting, forging, or cutting. Currently, the selective laser melting (SLM) process is considered suitable for biomedical applications because of its ability to fabricate parts that have complex shapes in small batches. Therefore, fabricating dental Co-Cr alloys by SLM is very promising. In the past few years, SLM manufacturing of cobalt-based alloys has developed rapidly and been evaluated by various researchers.[8–12] In recent years, many features of Co-Cr alloys fabricated by SLM were determined. Hedberg evaluated metal ions releasing into biologic fluids of a Co-Cr-Mo alloy fabricated by SLM and casting, concluding that specimens obtained by SLM have higher corrosion resistance than those from casting.[13] Xian-Zhen[14] and Wei[15] reached the same conclusion about Co-CrMo-W alloys through the electrochemical testing method. Furthermore, Takaichi evaluated the mechanical properties of the Co-29Cr-6Mo alloy manufactured by SLM and traditional methods and proved that the SLM-produced Co-29Cr-6Mo alloy has a higher yield strength and elongation.[16] The same conclusion was also obtained with Co-Cr-W and Co-Cr-Mo
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