钨含量对Ni-W-P镀层抗垢性能的影响

Effect of tungsten addition on the anti-fouling property of the electroless Ni-W-P deposits

摘要:

采用化学镀的方法，调整化学镀工艺参数中钨酸钠的浓度，在低碳钢（1015）表面获得了钨含量不同的Ni-W-P镀层，分别采用扫面电镜、X射线衍射仪以及MH-6表面硬度计研究了钨含量对Ni-W-P镀层表面形貌、结构以及显微硬度的影响。结果表明，镀液浓度对于获得磷和钨含量起到决定性的作用，而磷和钨的含量决定了Ni-W-P镀层的表面形貌和结构。胞状晶的形成是Ni-W-P镀层的共同特征，镀层中钨含量的增加降低了磷的含量，因此改变了纳米晶相的含量。由于钨固溶于镍中诱使镀层产生固溶强化限制了镀层局部塑性变形，从而增加了镀层的硬度。采用差热分析研究相变行为的结果表明，高钨含量的Ni-W-P镀层表现为较高的晶化温度。进一步的污垢沉积试验表明，与低碳钢表面相比，含有不同钨含量的Ni-W-P镀层表面抑制了污垢的黏附。然而，进一步研究表明，污垢沉积速度和Ni-W-P镀层表面粗糙度之间没有必然的联系，与钨的含量有着直接的联系。

Abstract:

In the present investigation, ternary Ni-W-P deposits were prepared on the mild steel (1015) substrate using electroless plating by varying sodium tungstate. Surface morphology, microstructure, and the microhardness of electroless Ni-W-P deposits were investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD) and a MH-6 Vickers diamond indenter, respectively. The results demonstrated that the bath concentration plays a significant role in obtaining ternary Ni-W-P deposits containing various composition of phosphorus and tungsten, which decides the surface morphology and the structure. Although nodular formation is a common feature of electroless Ni-W-P deposits, composition of W decreased the P content of these deposits and hence changes the content of the nanocrystalline phase. The co-deposition of tungsten in the deposits increased the microhardness due to the solid solution strengthening of nickel induced by tungsten in the deposits and resisted regional plastic deformation. Moreover, studies on phase transformation behavior carried out by differential scanning calorimetry (DSC) showed that Ni-W-P deposits with high W content exhibited higher crystallization temperatures. Further fouling experiments indicated that the Ni-W-P deposit surfaces with different W content inhibited the adhesion of fouling compared with the mild steel surface. However, we found there is not a necessary relationship between the fouling adhesion rate and surface roughness of the ternary Ni-W-P deposits, but is intimately related to the W content.