| CHEN Shu-nan,LOU Li-yan,JI Gang,JIA Yun-jie,LI Chang-jiu,LI Cheng-xin.Microstructure and Properties of Fe-based Alloy Prepared by Ultra-High Speed Laser Cladding and Conventional Laser Cladding[J],51(12):358-370 |
| Microstructure and Properties of Fe-based Alloy Prepared by Ultra-High Speed Laser Cladding and Conventional Laser Cladding |
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| DOI：10.16490/j.cnki.issn.1001-3660.2022.12.037 |
| KeyWord:ultra-high speed laser cladding coating microstructure corrosion resistance hardness phase structure |
| Author | Institution |
| CHEN Shu-nan |
National-local Joint Engineering Laboratory of Intelligent Manufacturing Oriented Automobile Die & Mould, School of Mechanical Engineering, Tianjin University of Technology and Education, Tianjin , China |
| LOU Li-yan |
National-local Joint Engineering Laboratory of Intelligent Manufacturing Oriented Automobile Die & Mould, School of Mechanical Engineering, Tianjin University of Technology and Education, Tianjin , China;State Key Laboratory for Mechanical Behavior of Materials, School of Materials Science and Engineering, Xi'an Jiaotong University, Xi'an , China |
| JI Gang |
State Key Laboratory for Mechanical Behavior of Materials, School of Materials Science and Engineering, Xi'an Jiaotong University, Xi'an , China |
| JIA Yun-jie |
National-local Joint Engineering Laboratory of Intelligent Manufacturing Oriented Automobile Die & Mould, School of Mechanical Engineering, Tianjin University of Technology and Education, Tianjin , China |
| LI Chang-jiu |
State Key Laboratory for Mechanical Behavior of Materials, School of Materials Science and Engineering, Xi'an Jiaotong University, Xi'an , China |
| LI Cheng-xin |
State Key Laboratory for Mechanical Behavior of Materials, School of Materials Science and Engineering, Xi'an Jiaotong University, Xi'an , China |
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| Abstract: |
| Ultra-high speed laser cladding (UHSLC) technology is a new developed green surface modification technology, which could realize the preparation of high quality coating with high efficiency of 50-500 m/min, and overcome the efficiency obstacle of conventional laser cladding (CLC) technology. The heat input to the substrate could be obviously decreased during UHSLC process, and the coating in thickness of 25-500 μm can be deposited with a dilution ratio as low as 2%. The UHSLC coating was reported to have better wear resistance and corrosion resistance, and the current explanation was due to the finer crystalline grain size and uniformly distributed elements, while the difference of the phase structure between the UHSLC and CLC coatings was not examined yet. In order to clarify the reason of the different performance of the CLC coating from UHSLC coating, the microstructure and phase structure of two different coatings were analyzed in this paper, and the relationship between the structure and the properties of the coating was established at the same time. Fe-based alloy coating was prepared on 27SiMn steel substrate. The laser cladding experiment was carried out with RFL-A2500D fiber laser of ϕ2 mm laser spot, and a self-designed co-axial powder feeding nozzle was chosen during the UHSLC process. The coating was deposited at a laser power of 2.5 kW with a linear speed of 15.6 m/min for UHSLC process, and 1.2 m/min for CLC process. The microstructure of the clad layer was characterized with scanning electron microscope (SEM), and the element analysis was analyzed using Energy-Dispersive Spectrometer (EDS). The phase composition was analyzed with X-ray diffractometer (XRD), optical microscope (OM), and electron backscattering diffraction (EBSD) technology. The micro hardness on the polished coating surfaces was measured by Vickers microhardness tester, and electro-chemical properties were characterized with electrochemical workstation. The experiment results showed that both the UHSLC coating and the CLC coating presented a dense microstructure with mainly dendritic structure, and no obvious pores and cracks were formed. The UHSLC coating was 200 μm in thickness with smooth surface, while the CLC coating was rough with the thickness of 800 μm. Moreover, the UHSLC coating presented finer grains and the more uniform element distribution with a lower dilution ratio of 2%, while the CLC coating presented, an inter-and intra-granular Cr content difference of 6% with a dilution ratio of 12%. The phase structure analysis results revealed that both the UHSLC coating and the CLC coating were composed of martensite, ferrite, and M-type carbides. However, since the higher nonequilibrium solidification rate and the higher content of Ni and Cr element suppress the evolution of martensite, the UHSLC coating had less content of martensite and carbides. Therefore, the UHSLC coating showed lower hardness (460HV) compared with the CLC coating (650HV). The electrochemical performance testing indicated the UHSLC coating had a better corrosion resistance, with the corrosion potential increased from –0.56 V to –0.51 V, and corrosion current density decreased from 1.3×10–5 A/cm2 to 1.5×10–7 A/cm2, compared with the CLC coating. This can be attributed to the fact that the UHSLC coating has higher Cr content, the distribution of Cr elements in the inter-and intra-granular is more uniform, and the intergranular corrosion could be inhibited. |
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