| SHENG Yongqi,WEI Yacheng,SHANG Dazhi,XIA Kun,SHENTU Chengwang,FENG Aixin.Microstructure and Properties of Laser Cladded Ni/WC Gradient Composite Coatings[J],53(15):152-162 |
| Microstructure and Properties of Laser Cladded Ni/WC Gradient Composite Coatings |
| Received:July 15, 2023 Revised:November 10, 2023 |
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| DOI：10.16490/j.cnki.issn.1001-3660.2024.15.014 |
| KeyWord:laser cladding Ni/WC gradient composite coating hardness wear resistance impact toughness |
| Author | Institution |
| SHENG Yongqi |
College of Mechanical and Electrical Engineering,Rui'an Graduate College, Wenzhou University, Zhejiang Wenzhou , China |
| WEI Yacheng |
College of Mechanical and Electrical Engineering,Rui'an Graduate College, Wenzhou University, Zhejiang Wenzhou , China |
| SHANG Dazhi |
College of Mechanical and Electrical Engineering, Beijing University of Chemical Technology, Beijing , China |
| XIA Kun |
College of Mechanical and Electrical Engineering,Rui'an Graduate College, Wenzhou University, Zhejiang Wenzhou , China |
| SHENTU Chengwang |
College of Mechanical and Electrical Engineering,Rui'an Graduate College, Wenzhou University, Zhejiang Wenzhou , China |
| FENG Aixin |
College of Mechanical and Electrical Engineering,Rui'an Graduate College, Wenzhou University, Zhejiang Wenzhou , China;Zhejiang Provincial Key Laboratory of Laser Processing Robots/Key Laboratory of Laser Processing and Testing in Machinery Industry, Zhejiang Wenzhou , China |
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| Abstract: |
| Cr12MoV is commonly used in molds for automotive seat frames. In practical applications, mold steel is subject to high impact forces and friction, ultimately leading to failure and affecting the service life of the mold. Laser cladding technology is currently an advanced surface repair technique. In order to improve the microhardness and wear resistance of the surface of Cr12MoV die steel and reduce the internal defects of the coating, in this paper, laser cladding technology was adopted to sequentially prepare Ni60-Ni60/25%WC (Ni/WC) gradient composite coatings on the surface of Cr12MoV steel. An X-ray diffractometer (XRD) was used to analyze the phase composition of the coating, a scanning electron microscope (SEM) was used to characterize the microstructure, an energy dispersive spectrometer (EDS) was used to analyze the element distribution of the coating, and a three-dimensional profilometer was used to observe the wear morphology. The hardness, wear resistance, and impact toughness of the gradient composite coating were tested with a microhardness tester, a friction and wear testing machine, and an impact testing machine, respectively. The research indicated that the Ni60 layer and the Ni60/25%WC layer achieved ideal metallurgical bonding when preparing Ni/WC gradient composite coatings on the substrate of Cr12MoV. The main phases on the surface of the Ni/WC gradient composite coating were γ-(Fe, Ni), FeNi3, CrB, Cr7C3, and Cr23C6. From the bottom to the top of the Ni60 layer, the microstructure transited from cellular crystals to columnar crystals, and finally to fine equiaxed dendrites. And from the performance point of view, the Ni/WC gradient composite coating exhibited a gradient distribution of hardness, which decreased with increasing depth. This was mainly due to the re-diffusion of alloying elements in the sub-surface layer after multiple cladding processes, resulting in a more uniformly distributed strengthening phase throughout the gradient coating. The average hardness of the coating reached 698.5HV, which was a 55.2% improvement compared with the substrate. Compared with the substrate, the Ni/WC gradient composite coating exhibited excellent wear resistance. The friction coefficient and wear rate were reduced by 40.92% and 28.6%, respectively. While the substrate showed adhesive wear, the coating as a whole demonstrated abrasive wear. This behavior was closely related to the increased hardness of the coating. The improved hardness of the Ni/WC gradient composite coating allowed it to resist wear caused by abrasive particles. The harder coating could effectively withstand the forces and interactions between the coating and abrasive particles, reducing the friction coefficient and wear rate. The presence of the gradient distribution in hardness further enhanced its resistance to wear, as different regions of the coating possess varying levels of hardness that contributed to its overall wear performance. However, compared with the substrate, the Ni/WC gradient composite coating exhibited a decrease of 32.48% in impact toughness value and showed brittle fracture behavior. Due to the presence of reinforcing phases in the coating, the material was more prone to crack propagation, while the lower impact toughness value limited its ability to absorb energy and inhibited crack propagation. This resulted in an increased likelihood of fracture occurring in the coating when it was subject to impact. In summary, the Ni/WC gradient composite coating exhibits good metallurgical bonding compared with the substrate. It effectively improves hardness and wear resistance. However, there is a slight decrease in impact toughness. |
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