| XIA Pengcheng,ZHAN Qingwei,XIE Kun,CAO Meiqing,YUE Lijie,SUN Xiaohua,DONG Junwei.Formation Mechanism of Reinforcements in NiAl Composite Coating and Its Effect on Wear Property[J],53(17):83-93 |
| Formation Mechanism of Reinforcements in NiAl Composite Coating and Its Effect on Wear Property |
| Received:September 18, 2023 Revised:March 04, 2024 |
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| DOI：10.16490/j.cnki.issn.1001-3660.2024.17.007 |
| KeyWord:NiAl composite coating thermodynamic calculation reinforcements hardness wear performance |
| Author | Institution |
| XIA Pengcheng |
School of Material Science and Engineering, Shandong University of Science and Technology, Shandong Qingdao , China |
| ZHAN Qingwei |
School of Material Science and Engineering, Shandong University of Science and Technology, Shandong Qingdao , China |
| XIE Kun |
School of Material Science and Engineering, Shandong University of Science and Technology, Shandong Qingdao , China |
| CAO Meiqing |
School of Material Science and Engineering, Shandong University of Science and Technology, Shandong Qingdao , China |
| YUE Lijie |
School of Material Science and Engineering, Shandong University of Science and Technology, Shandong Qingdao , China |
| SUN Xiaohua |
Qingdao Keruis Refrigeration Technology Co., Ltd., Shandong Qingdao , China |
| DONG Junwei |
Qingdao Keruis Refrigeration Technology Co., Ltd., Shandong Qingdao , China |
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| Abstract: |
| NiAl intermetallic compound has been widely used as a high temperature or coating material owing to its high ratio-strength and ratio-stiffness, good thermal conductivity and electric conductivity, excellent thermal stability and corrosion resistance. However, the hardness of NiAl compound is low, which results in inferior wear performance. Its application as a coating material is restricted. NiAl intermetallic coatings and TiC-TiB2/NiAl composite coatings were fabricated via the plasma cladding technology in the surface of Q235 low carbon steel. Microstructure characteristics, reaction thermodynamics, the formation mechanism of TiC-TiB2 ceramic reinforcement and tribological behavior of the coatings were discussed. The Q235 steel low carbon was used as substrate materials with the size of 100 mm×50 mm×5 mm in this experiment. Nickel powder, aluminum powder, titanium powder and boron carbide powder were used as raw materials of coatings. The matrix was Ni and Al with the atomic ratio of 1∶1. The TiC and TiB2 phases were fabricated by the reactions of 3Ti+B4C→TiC+2TiB2. The mass percent of TiC-TiB2 reinforcements was 20% in composite coatings. The powders were mixed by ball mill. Then they were blended with the sodium silica as binder and pressed on the surface of Q235 low carbon steel by tablet pressing machine. Coatings were prepared by DGR-5 plasma equipment. The microstructure of the coatings was observed by Axio Lab. Al optical microscope and high resolution scanning electron microscopy (HRSEM). The composition of samples was analyzed by JXA-8230 electron probe microprobe analysis (EPMA). The phase was identified by D/Max2500PC X-ray diffraction (XRD). Vickers microhardness was tested with a load of 0.98 N and 15 s of dwelling time in an FM-700/SVDM4R Automatic mico hardness tester. A sliding wear experiment of the sample was carried out with an M-2000 wear test machine. The friction coefficient of the coating was tested with a CETR-UMT-3 multifunctional testing machine. The coating was compact and uniform in addition to negligible porosity and had well metallurgical bonding with the substrate. Ni, Al and Fe elements diffused in the process of coating formation between the coating and the Q235 substrate. The NiAl coating was mainly composed of NiAl and the solid solution γ-(Fe, Ni) phases. The composite coating consisted of NiAl, Ni3Al, γ-(Fe, Ni), reinforcements of TiC and TiB2. The TiC phase had the shape of little block and TiB2 was the shape of short rod. The thermodynamic calculation of reaction further proved the microstructure formation. The formation mechanism of reinforcements was relevant with diffusion-precipitation and crystal structure. The microhardness of the composite coating increased from 416HV to 525HV and the friction coefficient and wear weightlessness decreased from 0.68 and 0.376 g to 0.54 and 0.192 g compared with that of the NiAl coating. There were many large and deep furrows on the worn surface of the NiAl coating, while the worn surface of the NiAl composite coating was relatively smooth with only shallow furrows missing. The NiAl composite coating has excellent wear property owing to its high hardness and low friction coefficient and wear weightlessness. The dispersed distribution of small TiC particles and the high microstructure stability of TiC-TiB2 are the main reason for the significant improvement in hardness and wear resistance in the cladding layer. The main wear mechanism of NiAl coatings is adhesive wear. The wear type of composite coatings is abrasive wear. |
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