Microstructure and Mechanical Properties of Two-Layer Laser-Cladded Co-Based Coatings
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Microstructure and Mechanical Properties of Two-Layer Laser-Cladded Co-Based Coatings Fengyuan Shu1 • Ye Tian1 • Jialiang Zhou1 • Wenxiong He1 • Hongyun Zhao1 Binshi Xu2
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Submitted: 25 January 2019 / in revised form: 21 June 2019 Ó ASM International 2019
Abstract Two-layer Co-based cladded coatings with hightemperature wear resistance were fabricated on the surface of Q235 steel by using laser cladding process. The microstructure and phase constitution of the cladded coatings were observed by SEM, EDS, XRD and TEM. The microhardness and high-temperature wear behaviors of the cladded coatings were evaluated by friction wear equipment. The microstructure of the upper region of the firstlayer cladded coatings showed a uniformly dendrite formation, while amorphous phase existed in the upper region of the second-layer cladded coatings because of the comparatively lower dilution in the upper layer. The microhardness of the second-layer cladded coatings was up to over 1200 HV0.2 which was six times of the substrate. The wear loss of the second-layer cladded coating was 18.3% less than that of the first-layer cladded coating. The secondlayer cladded coating possessed excellent comprehensive mechanical properties due to the existence of amorphous phase. Keywords amorphous phase Co-based cladded coatings laser cladding surface mechanical properties
& Hongyun Zhao [email protected]; [email protected] 1
Harbin Institute of Technology, Weihai Shandong Province Key Laboratory of Advanced Welding and Joining, Weihai 264209, Shandong, China
2
National Key Laboratory for Remanufacturing, Beijing 100072, China
Introduction Recent breakthroughs in surface modification technology have been widely adopted to improve the surface properties of certain engineered components (Ref 1, 2), such as excellent wear resistance, oxidation resistance and corrosion resistance to meet the requirements of engineering components under extreme environments. Laser cladding has been widely used as an advanced surface modification technique (Ref 3, 4) because of its high-energy density, good controllability, compact cladding microstructure, few microscopic flaw and high bonding strength (Ref 5). Cobalt-based alloy cladded coatings with high microhardness, high bonding strength, and excellent wear and corrosion resistance have a bright prospect for engineering applications. Previous researches on laser cladding mostly focused on structure and performance evaluation (Ref 6-8) including microstructure, wear resistance, phase constitution and corrosion resistance. Microstructure, phase and microhardness distribution of laser-cladded Ni-based amorphous cladded coating (Ref 5) were also studied. Shu (Ref 9) has fabricated amorphous cladded coating by using ordinary Co-based self-fluxed alloy powder and measured the temperature of supercooling liquid region. Wong (Ref 10) has analyzed formation and crystallization of amorphous structure in the laser-cladded coatings and found that the microhardness in the amorphous region is
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