Influences of Pulse Frequency on Microstructure and Properties in Laser Cladding Layers

doi:10.3969/j.issn.1004-132X.2021.17.012

Abstract

Abstract: The coarse grains and hard precipitates in the laser cladding layers had adverse effects on the corrosion resistance and impact resistance. The effects of pulse frequency on microstructure and properties of the coating were studied by pulse laser cladding technology. The microstructure of the coating was characterized by scanning electron microscope (SEM)morphology. High speed camera and numerical simulation method were used to analyze the shapes and temperature changes of molten pools. The hardness， wear resistance， impact resistance and corrosion resistance of the coating were tested by microhardness tester， wear tester， charpy impact tester and electrochemical corrosion tester respectively. The results show that the microstructure of the coating coarsens with the increase of pulse frequency. At the same time， the numbers of precipitates in the coating decrease first and then increase. The wear resistance of the coating decreases with the increase of pulse frequency. The wear resistance of the coating is the best because the microstructure of the coating is refined and there are fine hard precipitates at 20 Hz. The impact resistance and corrosion resistance of the coating increase first and then decrease with the increase of pulse frequency. Because the amount of hard phase in the coating decreases obviously at 80 Hz， the coating has the best impact resistance and corrosion resistance.

Key words: laser cladding, pulsed laser, microstructure, wear resistance, impact resistance, corrosion resistance

摘要： 激光熔覆层内粗大的晶粒与硬质析出相会对涂层耐腐蚀性能与耐冲击性能产生不利影响。采用脉冲激光熔覆技术研究了脉冲频率对涂层微观组织及性能的影响。利用扫描电镜形貌表征涂层微观组织，采用高速摄像机与数值仿真方法分析熔池形貌与温度变化；使用显微硬度计、磨损试验机、夏比冲击试验机及电化学腐蚀仪分别对涂层进行硬度、耐磨性、耐冲击性及耐腐蚀性测试。结果表明，涂层组织随脉冲频率的增大而粗化，同时，脉冲激光会使涂层内部析出相数量先减后增；涂层耐磨性随脉冲频率增大而降低，频率为20 Hz时涂层组织细化且存在细小硬质析出相，耐磨性最佳；涂层耐冲击性与耐腐蚀性随脉冲频率增大会先升后降，频率为80 Hz时涂层硬质相数量明显减少，此时具有最佳的耐冲击性与耐腐蚀性。

关键词: 激光熔覆, 脉冲激光, 微观组织, 耐磨性, 耐冲击性, 耐腐蚀性

CLC Number:

TN249

LI Yunfeng, SHI Yan, . Influences of Pulse Frequency on Microstructure and Properties in Laser Cladding Layers[J]. China Mechanical Engineering, 2021, 32(17): 2108-2117,2124.

李云峰, 石岩, . 脉冲频率对激光熔覆层微观组织与性能的影响[J]. 中国机械工程, 2021, 32(17): 2108-2117,2124.

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