First Demonstration of Additive Manufacturing of Cutting Tools using Directed Energy Deposition System: Stellite™-Based Cutting Tools

Abstract

Machine-tool concepts are becoming increasingly complex to meet the demanding requirements of advanced applications. This raises per-tool costs for manufacturers and end users, motivating the development of novel, innovative fabrication methods for these tools. Our objective herein is to investigate laser-based additive manufacturing to fabricate application-optimized machine-tools that perform comparably to commercially-available products. To demonstrate this technology, multi-layer Stellite™ (Co-Cr-W superalloy) structures were deposited on a stainless-steel substrate via directed energy deposition technique to be used as a tool for cutting applications requiring high-temperature strength and ductility, an area where conventional carbide and high-speed steel tools are challenged. The as-printed structures were free of large-scale defects and voids, and were further characterized and compared to commercial Blackalloy 525 barstock (B525), a Co-Cr-W alloy tool of similar composition. The Stellite™ contained mostly Co-rich (α-phase) dendrites, as well as inter-dendritic Cr7C3 and Cr23C6 phases. The B525 composition consisted of a range of lamellar-eutectic microstructure comprised of Co-phase with W6C reinforcement. In reciprocating wear testing, Stellite™ 6 maintained a steady-state COF within 20% of B525 (0.36 ± 0.01 vs. 0.30 ± 0.01), and final wear rate as low as 38% difference from B525 (5.14*10−6 ± 4.58*10−7Nmm3 vs. 3.20*10−6 ± 4.99*10-7Nmm3). During a turning operation of SS304L, the Stellite™ 6 tool demonstrated consistent chip formation and more consistent rake-face and cratering wear in comparison to the B525 tool, indicating its adequacy for service in this application. Our results demonstrate for the first time that directed-energy-deposition can be utilized to fabricate advanced cutting tool concepts for job-specific applications.