化学沉积非晶态Ni-W-P合金激光纳米化及其耐蚀机理研究
发布时间：2019-01-07 06:53
【摘要】：采用炉子和激光两种热源对镀层进行退火处理，比较了两种退火方式对镀层晶化组织、硬度和耐蚀性的影响。利用X射线衍射技术（XRD）定量分析了镀层的晶化程度、晶粒尺寸和微应变，并通过浸泡腐蚀失重和电化学极化实验对退火前后镀层的耐蚀性进行了研究，使用维氏显微硬度计测量各个镀层表面显微硬度，采用扫描电镜（SEM）和光学显微镜观察镀层腐蚀前后的表面形貌。 研究结果表明，化学沉积高磷含量的Ni-3.88wt%W-13.36wt%P合金镀层为非晶态结构，镀层的微应变和非晶相体积分数随退火温度的升高和激光扫描速度的降低而降低，而Ni_3P相和Ni相晶粒尺寸及其体积分数与之变化规律相反。炉子退火温度为400℃时，镀层中开始有Ni_3P相析出，且Ni_3P相的晶粒尺寸大于Ni相尺寸，温度超过500℃，两相的晶粒尺寸特征与之相反，激光退火镀层整个退火过程中均有Ni_3P相析出，且Ni_3P相晶粒尺寸始终大于Ni相，经两种方式退火镀层中各相晶粒尺寸大小均保持在纳米级。激光退火镀层的组织特征介于400~500℃之间炉子退火的组织特征。镀层的硬度随退火温度的升高而增大，在500℃达到最大，超过500℃时又有所下降；激光退火镀层的硬度随激光扫描速度的增大而减小，在8mm/s达到最大。激光退火镀层的硬度介于300～400℃之间炉子退火镀层的硬度，这种硬度向低值移动的现象归因于激光扫描轨迹在镀层表面形成搭接区的缘故。所有镀层在0.5M/L H2SO4溶液中的腐蚀失重和阳极极化中的腐蚀行为均表现为均匀腐蚀，镀态镀层的耐蚀性不高，主要与镀层中存在较大的内应力有关；退火晶化后镀层的耐蚀性增大，一方面归因于内应力的降低，另一方面则归因于Ni及Ni_3P两相晶粒尺寸及晶化程度的变化。此外，镀层中存在的孔洞也会相应的提高均匀腐蚀速率；激光退火镀层的耐蚀性高于炉子在400～500℃这一温度区间退火镀层的耐蚀性，相当于炉子在500～600℃退火镀层的耐蚀性。这一现象归因于激光退火镀层中形成的Ni_3P相远多于Ni相，使所构成的腐蚀微电池数量减少，从而提高了镀层的耐蚀性。
[Abstract]:The effect of two annealing methods on the microstructure, hardness and corrosion resistance of the coating was compared. The degree of crystallization, grain size and micro-strain of the coating were quantitatively analyzed by X-ray diffraction (XRD) technique. The corrosion resistance of the coating before and after annealing was studied by immersion corrosion loss and electrochemical polarization test. The microhardness of each coating was measured by Vickers microhardness meter. The surface morphology of the coating before and after corrosion was observed by scanning electron microscope (SEM) and optical microscope. The results show that the electroless Ni-3.88wt%W-13.36wt%P alloy coating with high phosphorus content is amorphous. The microstrain and amorphous phase volume fraction decrease with the increase of annealing temperature and the decrease of laser scanning speed. However, the grain size and volume fraction of Ni_3P phase and Ni phase are opposite to that of Ni phase. When the annealing temperature is 400 鈩，
本文编号：2403319
[Abstract]:The effect of two annealing methods on the microstructure, hardness and corrosion resistance of the coating was compared. The degree of crystallization, grain size and micro-strain of the coating were quantitatively analyzed by X-ray diffraction (XRD) technique. The corrosion resistance of the coating before and after annealing was studied by immersion corrosion loss and electrochemical polarization test. The microhardness of each coating was measured by Vickers microhardness meter. The surface morphology of the coating before and after corrosion was observed by scanning electron microscope (SEM) and optical microscope. The results show that the electroless Ni-3.88wt%W-13.36wt%P alloy coating with high phosphorus content is amorphous. The microstrain and amorphous phase volume fraction decrease with the increase of annealing temperature and the decrease of laser scanning speed. However, the grain size and volume fraction of Ni_3P phase and Ni phase are opposite to that of Ni phase. When the annealing temperature is 400 鈩，
本文编号：2403319
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