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目的：研究化学沉积Ni-4.11%Mo-6.50%P和Ni-9.19%P合金镀层退火晶化转变特征,通过定量表征镀层的晶化程度、晶粒尺寸及结晶相的质量分数,建立显微组织与耐蚀性的关联。方法采用XRD衍射技术和Jade软件分析,定量表征镀层的晶化组织特征,由SEM/EDS测试确定镀层的成分及表面形貌,通过浸泡腐蚀实验及金相显微观察,对比两种镀层的耐蚀性。结果 Ni-Mo-P镀层在低于400℃退火时,只有Ni相结晶；在≥400℃退火时,发生Ni3 P晶化反应,同时伴有Ni-Mo固溶体的形成,600℃时的晶化程度为88.13%。相比之下,Ni-P镀层中Ni3 P相开始析出的温度降至300℃,600℃时的晶化程度达到91%。在相同温度进行热处理时,Ni-Mo-P镀层晶粒尺寸小于Ni-P镀层。在发生Ni3 P晶化反应的温度下,两种镀层中Ni3 P的晶粒尺寸总是大于Ni相。在0.5 mol/L的H2 SO4中,对于Ni-Mo-P镀层,除300℃外,其他温度下的热处理均能显著改善其耐蚀性；而对于Ni-P镀层,镀态下具有最好的耐蚀性能。在10%的HCl溶液中,退火温度为600℃时,Ni-Mo-P镀层的耐点蚀性能更好；而Ni-P合金则相反,镀态及低温200℃退火后的耐点蚀性能最好。结论 Mo的共沉积提高了Ni-Mo-P镀层Ni3 P的析出温度,降低了镀层的晶化程度及晶粒尺寸；与Ni-P镀层相比,高温退火的Ni-Mo-P镀层表现出了优异的耐点蚀性能,但耐硫酸均匀腐蚀的性能较差。

Objective To study the crystallizing characteristics of Ni-4. 11%Mo-6. 50%P and Ni-9. 19%P coatings prepared by chemical deposition during annealing, and to establish the relationship between the microstructure and corrosion resistance by quan-titative characterization of crystallization degree, grain size and mass fraction of crystalline phases of the coatings. Methods The structural characteristics of coatings were quantitatively analyzed using XRD diffraction technique and Jade software;the morpholo-gy and composition of coatings were determined by SEM/EDS measurements; the corrosion resistance of both coatings was com-pared by immersion corrosion tests and metallographic microstructural observation. Results When the annealing temperature was below 400 ℃, only crystallized Ni phase existed in the Ni-Mo-P coating. The crystallization reaction of the Ni3 P phase occurred at 400 ℃ or above, and was accompanied by the formation of Ni-Mo solid solution. When the annealing temperature reached 600℃, the degree of crystallization of the Ni-Mo-P coating was 88. 13%. In contrast, when the precipitation temperature of Ni3 P phase in the Ni-P coating was lowered to 300 ℃, the degree of crystallization reached 91% at 600 ℃. The grain sizes of the Ni-Mo-P coa-ting were smaller than those of the Ni-P coating at the same annealing temperature. The grain size of Ni3 P phase was always larger than that of Ni phase at the crystallization reaction temperature of Ni3 P phase. In the 0. 5 mol/L H2 SO4 solution, for the Ni-Mo-P alloy, the heat treatment could significantly improve its corrosion resistance except at the annealing temperature of 300 ℃. For Ni-P alloy, the as-plated coating had the best corrosion resistance. In the 10% HCl solution, the Ni-Mo-P alloy annealed at the high temperature of 600 ℃ had higher resistance to pitting corrosion. For Ni-P alloy, it showed the opposite trend. The as-plated and annealed coatings at low temperature of 200 ℃ showed the best pitting corrosion resistance. Conclusion The co-deposition of Mo into Ni-P coating enhanced the precipitation temperature of Ni3 P phase and decreased the degree of crystallization and grain size. Compared with the Ni-P coating, the Ni-Mo-P coating annealed at high temperature exhibited better pitting resistance, but the resistance to uniform corrosion in H2 SO4 solution was lower.