ABSTRACT

The aim of the present study was to investigate the feasibility of fabrication of a Fe_53.4Cr₂₀Mo₁₆Cu_0.6C₁₀ amorphous and amorphous-crystalline crack-free layer with desirable corrosion resistance and hardness using the laser surface melting technique The phase analysis of clad layers has been characterised by X-ray diffraction (XRD). Also, the microstructure and phase analysis of the cross-section of clad layers has been studied by scanning electron microscopy, field emission scanning electron microscopy, and energy dispersive spectrometry. The effect of laser scanning speed on microstructure, corrosion behaviour, and hardness was investigated at 4, 6, and 8 mm s^-1. The results showed that a high fraction of amorphous phase (90%) has been obtained at an 8 mm s⁻¹ scan rate. The coating thickness is more than 150 μm, fully dense having low porosity. The corrosion resistance of Fe-based coatings was investigated by potentiodynamic polarisation and electrochemical impedance spectroscopic tests, and pitting corrosion evaluated in HCl solutions. The laser-treated material coatings had a lower current density than the substrate due to the formation of an amorphous phase, and the corrosion resistance values were 56, 162, and 141 Ω.cm² for 4, 6, and 8 mm s⁻¹ scanning rate samples respectively. It was found that high corrosion resistance is related to coating with a 6 m s⁻¹ scan rate due to the mixture of galvanic effects and amorphous structure. The average measured micro-hardness of the coatings demonstrated that the sample formed from the highest scan rate possessed the highest micro-hardness, which was 824 HV.

摘要

本研究的目的是研究使用激光表面熔化技术制备具有所需耐腐蚀性和硬度的 Fe _53.4 Cr ₂₀ Mo ₁₆ Cu _0.6 C ₁₀非晶和非晶晶无裂纹层的可行性。包层已通过 X 射线衍射 (XRD) 进行了表征。此外，还通过扫描电子显微镜、场发射扫描电子显微镜和能量色散光谱法研究了包层横截面的微观结构和相分析。在 4、6 和 8 mm s ^{-1下研究了激光扫描速度对微观结构、腐蚀行为和硬度的影响}. 结果表明，在 8 mm s ^-1扫描速率下获得了高比例的非晶相 (90%)。涂层厚度大于150μm，完全致密，孔隙率低。通过动电位极化和电化学阻抗光谱测试研究了铁基涂层的耐腐蚀性，并在 HCl 溶液中评估了点腐蚀。由于非晶相的形成，激光处理的材料涂层的电流密度低于基体，并且在4、6 和 8 mm s ^-1时的耐腐蚀性值为 56、162 和 141 Ω.cm ²分别扫描速率样本。发现高耐腐蚀性与具有 6 ms ^{-1的涂层有关}由于电流效应和无定形结构的混合而导致的扫描速率。涂层的平均测量显微硬度表明，由最高扫描速率形成的样品具有最高的显微硬度，为 824 HV。