退火處理及類鑽薄膜對無電鍍鎳鍍層磨耗腐蝕之影響

Effect of Annealing and Diamond-like Film on the Wear-corrosion of Ni Coatings Prepared by Electroless Plating

本研究以無電鍍退火處理及熱燈絲化學氣相沈積法（Hot Filament Chemical Vapor Deposition, HFCVD），為防止硬式磁碟機內部的鋁合金基板磁碟片（記憶磁訊號重要元件），因為記錄密度增加及磁頭飛行間距縮短而被磁頭刮傷，所以將對析鍍在鋁基板上的無電鍍鎳層施以不同溫度的退火處理（230℃~ 400℃）條件，另外並於鎳鍍膜表面濺鍍類鑽薄膜，來分析無電鍍鎳鍍膜與類鑽薄膜的組織結構、導電度及機械性質，進而探討鋁合金磁碟片在3.5 wt.% NaCl溶液下之磨耗腐蝕特性。
由組織結構、導電度及機械性質試驗分析結果顯示，退火處理溫度提高（230℃~ 400℃），使無電鍍鎳鍍膜內部結晶及組織轉化現象，由X-ray繞射分析鍍膜內含有NiP及Ni3P兩種結構，280℃所析出Ni3P結構較多，導電度的測試結果發現，隨著退火處理溫度提高導電度280℃> 260℃> 230℃的趨勢，因為較多的Ni3P結構，所以無電鍍鎳鍍膜之硬度也相對提升，證明此Ni3P結構的析出為硬化及強化機構，並且能提升導電度值。在磨耗腐蝕試驗中，將鍍膜浸置於3.5 wt.% NaCl腐蝕溶液下，以塊對環（block-on-ring）方式進行磨耗。結果顯示，280℃退火處理下其耐磨耗腐蝕性最差（icorr=3.68μA/cm2）、摩擦係數（μ）為0.87，而230℃退火處理其耐磨耗腐蝕性為較佳（icorr=2.37μA/cm2）、摩擦係數（μ）為0.45，因為退火處理溫度越高Ni3P結構越明顯，且導電度也是較高的趨勢，故耐磨耗腐蝕性下降。為了驗證是否隨著退火處理溫度越高進而導致抗腐蝕性下降，所以將退火溫度提高至400℃，分析出其較差的耐腐蝕性（icorr=5.99μA/cm2），證明是有此趨勢存在。為加強鍍膜退火處理之磨耗腐蝕性，所以於退火鍍膜表面濺鍍鑽石薄膜，藉此提升退火鍍膜之硬度、耐腐蝕磨耗性及耐腐蝕性，並且做一系列的研究。

This research is to evaluate the effect of both the post-annealed NiP and the DLC thin film on the wear corrosion properties of aluminum magnesium planks, with an annealing process being conducted at different temperatures (230 ℃ ~ 280 ℃, 15 min). The aluminum plank floppy disk (an important component for recording the magnetism signal) is the in bar of a hard disk inner part. As the recording density increases and the fly time of the magnetic head shortens, the disk will be scratched and damaged by the head. In this study, NiP films electrolessly plated on aluminum plates and a DLC thin film deposited on one of the NiP films by sputtering were prepared. The structures, electric conductivity, mechanical properties, and wear-corrosion characteristics in 3.5 wt.% NaCl solutions of the NiP film and the DLC thin film were then analyzed.
The results indicate that the NiP film contained both NiP and Ni3P phases, according to the X-ray diffraction analysis. The Ni3P phase gradually increased with increasing annealing temperature. The electric conductivity of the film was also found to behave similarly since the hardness of the NiP film increased with more Ni3P phase. In the wear corrosion test, the NiP film annealed at 280 ℃ exhibited a corrosion current density (icorr) of 3.68 μA/cm2 and a friction coefficient of 0.87, both worse than those annealed at 230 ℃ and 260 ℃ in the aspect of wearcorrosion resistance. The annealing temperature was later raised to 400 ℃, and the icorr on the NiP film was further increased to 5.99 μA/cm2, confirming the effect of elevated temperature. On the other hand, test results on the DLC thin film of 3nm in thickness deposited on the NiP film annealed at 280 ℃ showed an icorr of 2.87 μA/cm2 and a friction coefficient of 0.78, a significant improvement on the wear corrosion resistance as compared with that of the bare film. Similar improvements were also found on the DLC thin films deposited on the NiP films annealed at other temperatures.