【摘要】：采用爐子和激光兩種熱源對鍍層進行退火處理，比較了兩種退火方式對鍍層晶化組織、硬度和耐蝕性的影響。利用X射線衍射技術(shù)（XRD）定量分析了鍍層的晶化程度、晶粒尺寸和微應變，并通過浸泡腐蝕失重和電化學極化實驗對退火前后鍍層的耐蝕性進行了研究，使用維氏顯微硬度計測量各個鍍層表面顯微硬度，采用掃描電鏡（SEM）和光學顯微鏡觀察鍍層腐蝕前后的表面形貌。 研究結(jié)果表明，化學沉積高磷含量的Ni-3.88wt%W-13.36wt%P合金鍍層為非晶態(tài)結(jié)構(gòu)，鍍層的微應變和非晶相體積分數(shù)隨退火溫度的升高和激光掃描速度的降低而降低，而Ni_3P相和Ni相晶粒尺寸及其體積分數(shù)與之變化規(guī)律相反。爐子退火溫度為400℃時，鍍層中開始有Ni_3P相析出，且Ni_3P相的晶粒尺寸大于Ni相尺寸，溫度超過500℃，兩相的晶粒尺寸特征與之相反，激光退火鍍層整個退火過程中均有Ni_3P相析出，且Ni_3P相晶粒尺寸始終大于Ni相，經(jīng)兩種方式退火鍍層中各相晶粒尺寸大小均保持在納米級。激光退火鍍層的組織特征介于400~500℃之間爐子退火的組織特征。鍍層的硬度隨退火溫度的升高而增大，在500℃達到最大，超過500℃時又有所下降；激光退火鍍層的硬度隨激光掃描速度的增大而減小，在8mm/s達到最大。激光退火鍍層的硬度介于300～400℃之間爐子退火鍍層的硬度，這種硬度向低值移動的現(xiàn)象歸因于激光掃描軌跡在鍍層表面形成搭接區(qū)的緣故。所有鍍層在0.5M/L H2SO4溶液中的腐蝕失重和陽極極化中的腐蝕行為均表現(xiàn)為均勻腐蝕，鍍態(tài)鍍層的耐蝕性不高，主要與鍍層中存在較大的內(nèi)應力有關；退火晶化后鍍層的耐蝕性增大，一方面歸因于內(nèi)應力的降低，另一方面則歸因于Ni及Ni_3P兩相晶粒尺寸及晶化程度的變化。此外，鍍層中存在的孔洞也會相應的提高均勻腐蝕速率；激光退火鍍層的耐蝕性高于爐子在400～500℃這一溫度區(qū)間退火鍍層的耐蝕性，相當于爐子在500～600℃退火鍍層的耐蝕性。這一現(xiàn)象歸因于激光退火鍍層中形成的Ni_3P相遠多于Ni相，使所構(gòu)成的腐蝕微電池數(shù)量減少，從而提高了鍍層的耐蝕性。
[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，

本文編號：2403319