預鍍鎳層對低碳鋼熱浸鍍鋁於高溫擴散之作用

Effect of Nickel Plating on the High-Temperature Diffusion Behavior of Al Hot-Dipped Low Carbon Steels

本研究於低碳鋼表面以電鍍方式鍍鎳層再進行熱浸鍍純鋁後，於750℃靜滯空氣進行恆溫氧化與熱循環實驗，探討鎳鋁化塗層之相變化過程與動力學，並和低碳鋼熱浸鍍純鋁比較兩者鍍層之抗氧化性及熱循環行為。實驗結果顯示，預鍍鎳低碳鋼熱浸鋁化塗層，由表面至基材分別為純鋁塗層、NiAl3、Ni2Al3、NiAl、Ni3Al與純鎳層。經短時間擴散後，純鋁塗層與NiAl3轉變為Ni2Al3，經120小時擴散，大部份Ni2Al3變為NiAl相。鎳鋁化層中的鎳鋁交互擴散，在NiAl比Ni3Al有較低的活化能障，造成NiAl成長速率較高。預鍍鎳低碳鋼熱浸鋁與低碳鋼熱浸鍍純鋁相比，在高溫空氣環境具有較優異的抗氧化性與受熱循環後之表現。

The purpose of this study was to investigate the effects of nickel-plating on the phase transformation, kinetics, and thermal-cycling oxidation behavior of Al hot-dipped low-carbon steels at 750 ℃ in dry air. The results were compared with those of the same steel with a direct Al hot-dipping (without Ni-plating). The results showed that Ni-Al layers having formed in the top coating consisted of NiAl3, Ni2Al3, NiAl, Ni3Al, and pure-nickel layers. However, most Ni2Al3 phase was transformed into a NiAl phase after a 120 hr exposure. Due to the lower activation energies for the growth of both NiAl and Ni3Al phases, their growth rates were much faster than those of the other Ni-Al phases. It was found that the steel with the nickel-plating treatment exhibited an excellent oxidation and thermal-cycling resistance with respect to that of the nickel-plating free steel.