Abstract

Cemented Tungsten carbides (WC-X) have been a mainstay for wear components across many different industries including oil & gas. These ceramic-metal (cermet) systems can be widely tailored to optimize their wear resistance, corrosion resistance and toughness properties to suit their functional requirements. Conventional powder metallurgy has been the process of choice for these cermets whereby tungsten carbide powder along with a choice of metallic binder (cobalt, nickel, or alloyed binder) are pressed into a desired shape and subsequently sintered. There are manufacturing limitations to traditional powder metallurgy for parts containing high geometric complexity. In addition, secondary processing required to create complex features on press-sintered parts such as electro discharge machining (EDM) can sometime lead to micro cracking in the re-cast layer, which subsequently leads to part failure during operation. Additive manufacturing (AM) can produce cemented carbides with complex part geometry, significant weight reduction, and elimination of subsequent secondary processing to these parts. Although several AM methods have been investigated to additively manufacture cemented carbides, the present study utilized a binderjet process to manufacture two relatively low binder containing WC-Co grades; WC-17%Co and WC-13.5%(Co+Ni+Cr+Mo). The corrosion, wear, and mechanical properties of AM cemented carbides grades were characterized in the present study. Corrosion properties of the AM grades as well as their equivalent grades fabricated using conventional PM route were compared using linear polarization resistance and cyclic potentio-dynamic polarization following methods outlined in ASTM G59 and ASTM G61, respectively, in neutral 3.5% NaCl solutions. Mechanical characterization was performed using fracture toughness testing per ASTM B771 as well as transverse rupture toughness testing per ASTM B406 on these grades. Wear properties were examined according to ASTM G65 and B611. Optical and scanning electron microscopic techniques were further utilized to characterize and compare the microstructures of the samples manufactured using these two processing routes. The effect of microstructure on the resulting mechanical properties of the AM parts is also addressed in this study.

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