Surface & Coatings Technology 438 (2022) 128374 Available online 26 March 2022 0257-8972/© 2022 Elsevier B.V. All rights reserved. Micro-abrasive wear resistance of heat-treated electroless nickel‑phosphorus coatings deposited on copper‑beryllium alloy C17200 T.M. Reis, C.D. Boeira, F.L. Serafni, M.C.M. Farias, C.A. Figueroa, A.F. Michels * Graduate Program in Materials Science and Engineering, University of Caxias do Sul (UCS), 95070-560 Caxias do Sul, RS, Brazil A R T I C L E INFO Keywords: Copper‑beryllium alloys Electroless nickel‑phosphorus coating micro-abrasive wear ABSTRACT Copper‑beryllium alloys are widely used to manufacture thermoplastics injection molds due to their high thermal conductivity. Even though these alloys admit precipitation hardening at temperatures between 250 and 400 ◦ C, they still call for surface coatings to enhance their abrasion resistance. However, application of these coatings can generate over-aging under specifc deposition temperature ranges. This phenomenon causes a loss of substrate mechanical properties, making some industrial applications unfeasible, for example: construction of core pins with high slenderness ratio, and cores and cavities injection mold with narrow closure regions. This work pro- poses a solution to increase abrasive wear resistance of copper‑beryllium alloy C17200 through an electroless nickel‑phosphorus (Ni – P) coating. Temperature used in heat treatment of the coating was lower than substrate aging temperature. In this work, the heat treatment was carried out at 200 ◦ C for 24 h. Hardness of coating and substrate was evaluated by measuring the cross-sectional microhardness profle after heat treatment. Micro- structure, chemical composition, and crystallinity of coating and substrate were characterized using scanning electron microscopy (SEM), glow discharge optical emission spectroscopy (GD-OES), and X-ray diffraction (XRD), respectively. Wear behavior of coating-substrate systems was evaluated by micro-abrasive wear tests optical proflometry and SEM. Ni – P coating combined with heat treatment increased the surface hardness from 340 HV for uncoated alloy to an average of 997 HV for coated and heat treated alloy while maintaining substrate hardness. The application of this coating reduced the wear coeffcient in the order of 3.03 × 10 6 to 2.04 × 10 6 (mm 3 N 1 m 1 ). All the conditions analyzed, showed a mixed micro-abrasive wear mechanism with rolling and grooving wear characteristics. 1. Introduction The use of high thermal conductivity materials in thermoplastic in- jection molds has led to an injection cycle reduction and effciency processes increase [1]. Copper‑beryllium alloys have been used widely in this application due to their high thermal conductivity and strength [2]. However, the low abrasion resistance of these alloys has limited their application in injection molds, especially for molding operations of polymer matrix composites containing abrasives fber reinforces and fllers [3]. Copper‑beryllium alloys surfaces have been modifed with hard wear-resistant coatings to overcome these issues [4,5]. Several studies have been carried out to increase the wear resistance of Cu alloys for molds through surface treatments. Physical vapor depositions (PVD) coatings combined with electroless nickel‑phosphorus interlayer [6,7] or duplex treatments of magnetron sputtered flm, and plasma nitriding treatments result in improved wear resistance of copper‑beryllium alloys [8–12]. Copper‑beryllium alloy C17200 can be hardened by precipitation. In most industrial applications, the aging treatment of these alloys occurred at temperatures between 250 and 400 ◦ C for 0.1 to 4 h, which provides an alloy with a hardness between 320 and 400 HV [13–15]. Precipitation hardening treatment leads to homogeneous nucleation of Guinier-Preston (G-P) zones. As the precipitation stage progresses, the following sequence of precipitate formation occurs from the G-P zones: initially, the formation of meta-stable coherent precipitates ℽ" with body-centered tetragonal structure occurs [16], followed by the for- mation of ℽ' precipitates with bcc structure and ending with the for- mation of the ℽ phase, which is a stable phase with bcc structure CsCl type [13,15,17]. Below about 330 ◦ C, age hardening takes place almost exclusively from formation of metastable coherent precipitates. Above this temperature, both metastable and equilibrium precipitates are formed where the latter is mostly concentrated at grain boundaries [15]. * Corresponding author at: Francisco Getúlio Vargas Street, 1130 Caxias do Sul, RS, Brazil. E-mail address: afmichels@ucs.br (A.F. Michels). Contents lists available at ScienceDirect Surface & Coatings Technology journal homepage: www.elsevier.com/locate/surfcoat https://doi.org/10.1016/j.surfcoat.2022.128374 Received 13 January 2022; Received in revised form 7 March 2022; Accepted 20 March 2022