氮化處理對塑膠模具鋼之表面特性研究

A Study of Surface Properties for Plastic Mold Steel by Nitriding Treatment

呂志宏(Chih-Hung Lu)

指導教授 ： 韓麗龍 ； 施議訓

國立臺北科技大學/機電學院/機電整合研究所/碩士(2011年)

摘要

AISI P21為組織均匀之預硬鋼，因具有極佳的放電加工、精密咬花及焊接性等，故非常適用於塑膠模具鋼鏡面抛光之模仁與模穴使用。本研究針對P21施以三種不同製程參數之氣體氮化與氮氧化處理，探討氮化後對模具鋼表面特性之影響。製備後的試片以 OM 分析氮化層的顯微結構與氮化層厚度；以X 光繞射儀分析氮化層結構；以EDS 分析氮化層成份；以3D 表面輪廓儀分析氮化層表面形貌及表面粗糙度；以接觸角試驗來分析氮化層之親、疏水性；藉由極化腐蝕及浸泡試驗來分析氮化層抗腐蝕特性；以微硬度試驗來測試氮化層硬度與驗證氮化層深度；以洛氏壓痕試驗來觀察氮化層的附著性；用磨耗試驗來評估氮化後的耐磨耗性與摩擦係數，最後以SEM 觀察氮化層表面形貌、確認磨耗機制及作附著性等級之判別。
實驗結果顯示氮化處理後之AISI P21 塑膠模具鋼，可以有效提升表面之硬度、耐磨耗性與附著性，其中以氮氧化處理具有較佳的耐磨耗性與較低的腐蝕電流。另因氮元素在表層深處形成Fe3N 及Fe4N ，具有良好的硬度且脆性較低之氮化鐵可確保塑膠模具之尺寸精度與使用壽命。

關鍵字

AISI P21 ； 氣體氮化 ； 氮氧化 ； 耐磨耗性 ； 摩擦係數 ； 腐蝕電流

並列摘要

AISI P21 prehardened plastic mold steel containing homogeneous microstructure, good EDM properties, precise texture, and weldability etc. is suitable for mirror finished plastic mold core and cavity. This study applied nitriding heat treatment and oxynitriding to AISI P21 plastic mold steel with different processing parameters to explore the influence on the surface characteristics by the nitriding treatment. For the prepared test piece, OM was utilized to analyze the microstructure and nitride layer thickness, XRD was employed to examine the structure, EDS was used to investigate the compositions, 3D surface profile meter was adopted to scrutinize the surface morphology and roughness, contact angle test was made to give an analysis of the hydrophilicity and hydrophobicity, and polarization corrosion and immersion test was conducted to analyze the corrosion resistance. In addition, micro-hardness test was implemented to test the hardness and verify the nitride layer depth, Rockwell indentation test was carried out to observe the adherence, wear test was given to assess the wear resistance and friction coefficient, and finally, the surface profile was observed by SEM to determine the wear mechanism and the level of adherence.
Results show the nitrided AISI P21 plastic mold steel can effectively improve the surface hardness, wear resistance and adherence. The surface nitride layer underthe oxynitriding also effectively relieves the corrosion resistance and decreases the corrosion current. Furthermore, the nitrogen element under the surface layer produces the ferrous nitrides, such as Fe3N and Fe4N, which is of good hardness but low brittle, so that the size of plastic mold is maintained precisely, and the life of are extended.

並列關鍵字

AISI P21 ； gas nitriding ； oxynitriding ； wear resistance ； friction coefficient ； corrosion current

參考文獻

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