| XIA Jun-jia,YIN Yu,ZHOU Chen,ZHANG Shu-ling,GUO Feng,MA Xing-hua.Effects of Graphite Powder on Microstructure and Properties of WC Reinforced Ni-based Composite Coatings[J],52(7):139-148, 287 |
| Effects of Graphite Powder on Microstructure and Properties of WC Reinforced Ni-based Composite Coatings |
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| DOI：10.16490/j.cnki.issn.1001-3660.2023.07.011 |
| KeyWord:laser cladding WC/Ni60A coating graphite microstructures wear and corrosion resistance |
| Author | Institution |
| XIA Jun-jia |
Qingdao University of Technology, Shandong Qingdao , China |
| YIN Yu |
Qingdao University of Technology, Shandong Qingdao , China |
| ZHOU Chen |
Qingdao University of Technology, Shandong Qingdao , China |
| ZHANG Shu-ling |
Qingdao University of Technology, Shandong Qingdao , China |
| GUO Feng |
Qingdao University of Technology, Shandong Qingdao , China |
| MA Xing-hua |
Qingdao University of Technology, Shandong Qingdao , China |
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| Abstract: |
| Laser cladding ceramic reinforced metal matrix composite (MMC) is a new surface modification technology, which combines excellent mechanical properties of metal and excellent wear resistance of ceramic. In this work, with WC ceramics of high hardness and chemical stability as reinforcement phase and Ni60A as binder, crack-free WC reinforced Ni-based composite coating was prepared on H13 steel matrix. The effect of different contents of WC particles on the microstructure and properties of the coating was studied. Meanwhile, multilayer grapheme-like structure was generated from graphite powders by ultrasonic stripping and wet ball milling to further improve the wear and corrosion resistance of WC/Ni60A coating. The specimens with dimensions of 35 mm×15 mm×10 mm, cut from H13 steel, were used as matrixes, and the cladding coating was prepared by coaxial powder feeding method with FL020 fiber laser. During the cladding process, the laser power was 1 400 W, the spot diameter was 2 mm, the scanning speed was 7 mm/s, the overlap rate was 40%, and the powder feeding rate was 15~20 g/min. Firstly, multi-content WC (15 wt.%, 25 wt.% and 35 wt.%) reinforced Ni60A-based coatings were prepared. SEM, EDS and XRD were used to analyze the microstructures, element distribution and phase composition of the coatings. The wear and corrosion resistance of the coatings were tested by UMT, morphology microscope and electrochemical workstation, and the addition amount of WC with the best properties was selected. Next, varied amount of graphite powders (0.25 wt.%, 0.5 wt.%, 0.75 wt.% and 1.0 wt.%) pre-treated by ultrasonic were added into the specimen with the best properties, and during the ball milling process, the pre-treated graphited powders were further reduced into graphene-like structures, and the corresponding microstructures, corrosion and wear resistance were further evaluated. The microstructures of the composite coatings prepared by laser cladding were compacted, with metallurgical bonding with the matrix. The microstructure of cladding coating mainly consisted of plane crystal at metallurgical junction, columnar crystals in the middle and disordered cellular dendrites at the top. The cladding coating was mainly composed of γ-Ni dendrites and (Ni, Cr, Fe) and (Fe, Ni) solid solutions. At the same time, due to WC decarbonization, hard phases such as Cr23C6, SiC, B4C and W2C were easily generated, which effectively improved the hardness of the coating. When the addition amount of WC achieved 25 wt.%, the corrosion and wear resistance of the WC/Ni60A coating was the best. The microstructures of the coating, which was prepared on the graphite modified WC reinforced Ni60A alloy, was refined due to the addition of graphite. At the same time, the partially melted graphite powder played a good self-lubricating role in the cladding coating, which reduced the friction coefficient. The corresponding wear and corrosion resistance was also be enhanced. When the amount of graphite was 1.0 wt.%, the coefficient of friction of the coating stabilized at 0.25 and the wear rate was approximately 0.003 2 cm3/(N.m). The wear resistance was 3 times that of H13 steel matrix and 2 times that of 25 wt.% WC/Ni60A composite coating. Therefore, the graphite/WC/Ni60A is expected to be a new surface protective material for extreme marine environment. |
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