Pulsed laser processed NiCrFeCSiB/WC coating versus coatings obtained upon applying the conventional re-melting techniques: Evaluation of the microstructure, hardness and wear properties

• Published in: Surface & coatings technology 2019-09, Vol.374, p.1091-1099
• Main Authors: Škamat, Jelena, Černašėjus, Olegas, Čepukė, Živilė, Višniakov, Nikolaj
• Format: Article
• Language: English
• Subjects: Flame fusing; Hardness; Induction heating; Laser beam heating; Laser processing; Lasers; Melting; Metal matrix composites; Metallurgy; Microhardness; Microstructural analysis; Microstructure; Morphology; Ni-WC coating; Nickel; Process parameters; Protective coatings; Pulsed lasers; Substrates; Thickness; Tungsten carbide; Ultrafines; Wear rate; Wear resistance
• ISSN: 0257-8972; 1879-3347
• DOI: 10.1016/j.surfcoat.2019.06.080

In the present work, the influence of pulsed laser re-melting on the structure, hardness and wear resistance of Ni-WC metal matrix composite (MMC) coatings was investigated. The NiCrFeCSiB/40%WC powder was used for experiments. The microstructural analysis upon applying the scanning electron microscopy, energy dispersive spectroscopy and X-ray diffractometry was conducted along with microhardness measurements and wear resistance tests. The obtained properties of laser-processed layers were compared with the analogical coatings re-melted using three different conventional heating techniques. The evolution of the structure in Ni-WC layers during heating was studied and it was found that upon using conventional heating techniques, the optimal microstructure of the WC containing Ni-based coating that provided the highest hardness (~880 HK) and the best wear resistance was obtainable in a narrow range of heating duration. An incomplete re-melting process results in an absence of metallurgical bond between coating and substrate. When overheated, tungsten carbides dissolve in metal matrix. The laser processing provided stable ultrafine W-rich dendrites in Ni-rich matrix microstructure of deposited layer, which morphology did not change significantly with variation of the process parameters. The size of the finest tungsten-rich particles was about 200 nm and the hardness reached ~990 HK, providing 12–31% improvement as compared with the best results of induction, furnace, and flame heating. The wear rate of laser processed coating was 12% (by mass loss) and 42% (by thickness of removed layer) lower as compared with the highest results for conventionally heated coatings. •The evolution of NiCrFeCSiB/40%WC coating microstructure during conventional heating is studied.•High 880 HK hardness of conventionally heated coatings is obtainable in a narrow duration range.•Pulsed laser processing provides stable ultrafine microstructure of NiCrFeCSiB/40%WC coatings.•Pulsed laser processing provides ~990 HK hardness of NiCrFeCSiB/40%WC coatings.