Laser hot-wire cladding of Ni/WC composite coatings with a tubular cored wire

Abstract

Ni/WC composite coatings were successfully prepared on carbon steel by the method of laser hot-wire cladding with a tubular cored wire. The processing characteristics, phases compositions, microstructural evolution, and wear resistance of the coatings were systematically investigated. A high-speed camera was used to investigate the wire transfer behaviors under various processing parameters which included the laser power of 1000 W, wire feeding speed of 4 mm/s, laser scanning speed of 2 mm/s, and different preheating currents (0∼100A). Three typical wire transfer modes including wire stubbing transfer (0∼50A), wire plunging transfer (55∼80A), and wire fusing transfer mode (90∼100A) were obtained. The coating microstructure was mainly consisted of the retained particles, Ni-dendrites, Ni/Ni3B eutectic structure, and various kinds of precipitations including WC, W2C and M6C (M = Fe, Ni, W) carbides. It was found that the wire transfer mode was a critical factor of influencing the geometrical and microstructural characteristics of the coatings. The WC particles could be generated in the coatings when the lower dilution degree (0.8∼1.2 %) was obtained under the wire stubbing transfer mode. When the wire plunging transfer was produced as the total energy input was increased, the homogeneously distributed W2C particles could preferentially be precipitated in the coatings with a relatively low dilution (1.9∼7.9 %). The M6C carbides were mainly formed in the coatings with a high dilution ratio (12.1∼13.9 %) fabricated under the wire fusing transfer mode. The coatings fabricated under wire plunging transfer mode exhibited higher wear resistance which was about 31∼51 times higher than that of substrate.