不同工作週期對直流脈衝電漿化學氣相沉積法蒸鍍DLC薄膜於氮氧化處理JIS SKD11工具鋼之研究

Study on the DLC Films of Oxynitriding-treated JIS SKD11 Tool Steel via Various Duty Cycles of DC-pulsed PECVD Process

余鈞正(Chun-Cheng Yu)

指導教授 ： 張世賢

共同指導教授 ： 劉沖明

國立臺北科技大學/工程學院/材料科學與工程研究所/碩士(2014年)

摘要

JIS SKD11工具鋼是常用的冷作模具鋼之一，其擁有高耐磨耗性質與適宜的韌性，因此常應用在壓沖模具及塑膠模具等多功能方面，為了提高刀具的使用壽命，更常使用表面處理來保護內部材料。氮氧化處理可形成許多種類的氮化物(Fe2N、Fe3N和Fe4N)以及氧化物(Fe2O3和Fe3O4)，而其中Fe3O4的氧化層可以有效的防止並改善鋼鐵的耐侵蝕性與耐腐蝕性。類鑽碳(DLC)薄膜具有很多優越的性質，如高硬度、高磨耗阻抗、低磨擦係數及化學鈍性等等；此外，值得一提的是使用直流脈衝電漿化學氣相沉積法，可以有效地改善並提高薄膜的附著力與薄膜性質。因此本實驗使用氮氧化/類鑽碳鍍膜的複合處理於SKD11工具鋼上進行表面改質，嘗試以此複合表面處理來增加其使用壽命。
本研究中使用直流脈衝電漿化學氣相沉積法，將類鑽探薄膜沉積於氮氧化處理後的SKD11工具鋼上；主要探討的直流脈衝電漿化學參數，包括單極性負脈衝電壓與非對稱式雙極脈衝電壓，為了探討DLC薄膜的性質，我們利用拉曼光譜分析、磨耗測試、附著性測試、硬度測試及腐蝕試驗等，來檢測其薄膜之特性。
本實驗結果顯示，JIS SKD11工具鋼的氮氧化層有效硬化深度大約為46 μm，並且成功的在其氮氧化後的試片表面上沉積1-2 μm的類鑽探薄膜，而且其所有參數的薄膜被覆性都相當優越，其中又以脈衝電壓為-1.5 kV，沉積90分鐘以及工作週期為-15+10%的非對稱式雙極脈衝電壓擁有最佳的薄膜性質，其表面硬度最高可達Hv0.025 2830.7，並且在所有不同磨耗參數的變化中都擁有最低之磨耗體積損失(在滑動速度0.05 m•s-1及荷重200 g 時，為4.07 × 10-3 mm3；在滑動速度0.25 m•s-1及荷重 200 g 時，為4.01 × 10-3 mm3；而在滑動速度0.25 m•s-1及荷重500 g 時，為5.83 × 10-3 mm3)。此外，在腐蝕試驗中，氮氧化/DLC複合表面處理在3.5 wt% NaCl腐蝕環境下有最低的腐蝕電流(2.66 × 10-6 A•cm-2)及最高的極化電阻(1.57 × 104 Ω•cm2)，這些結果均表示其擁有最佳的耐磨耗與耐腐蝕性質。

關鍵字

SKD11工具鋼 ； 氮氧化處理 ； 類鑽碳模 ； 直流脈衝電漿化學氣相沉積法 ； 雙極脈衝 ； 磨耗

並列摘要

JIS SKD11 tool steel is a commonly used cold work tool steel. Due to its high wear resistance and appropriate toughness, SKD11 is often using for stamping molds, plastic molds and other multi-function items. To improve tool life, many studies have focused on surface treatment as a method of protecting the internal material. The oxynitriding process can form several kinds of nitride (Fe2N、Fe3N and Fe4N) and oxides (Fe2O3 and Fe3O4). Generally, the Fe3O4 layer of oxidation treatment can effectively protect and improve the erosion and corrosion resistance of steels. Diamond-like carbon (DLC) films have many superior properties, such as high mechanical hardness, high wear resistance, a low friction coefficient and chemical inertness. In addition, the adhesion and properties of DLC film can be effectively improved by a DC-pulsed discharge of the plasma CVD process. Therefore, the oxynitriding/DLC duplex treatment is utilized for treated SKD11 tool steel in an attempt to increase tool life.
In this study, diamond-like carbon films were prepared by DC-pulsed PECVD after oxynitriding-treatment of SKD11 tool steel. The chief study of the parameters of a DC-pulsed PECVD process included the duty cycles with unipolar negative-pulsed voltage and unbalanced bipolar-pulsed voltage. In order to evaluate the properties of the DLC films for oxynitriding/DLC-treated SKD11 tool steel, Raman spectroscopy analysis, wear tests, scratch tests, hardness tests and corrosion resistance inspections were performed.
The experimental results showed that a 46 μm oxynitride layer and 1-2 μm of DLC thin film could be successfully obtained after the JIS SKD11 tool steel was treated by the oxynitriding/DLC duplex treatment. All the DLC films of the oxynitride/DLC duplex treatment possessed good adhesion and excellent characteristics. Particularly, the duplex coating layers had optimal properties when DLC films were treated by an unbalanced bipolar pulse voltage, with a low pulse voltage (-1.5 kV), a coating time of 90 min and duty cycles maintained at -15+10%. Meanwhile, the oxynitride/DLC duplex treatment possessed the highest surface hardness (Hv0.025 2830.7) and lowest wear volume loss (when the sliding speed of 0.05 m•s-1 and load of 200 g was 4.07 × 10-3 mm3; sliding speed 0.25 m•s-1 and load 200 g, was 4.01 × 10-3 mm3; sliding speed 0.25 m•s-1 and load 500 g, was 5.83 × 10-3 mm3, respectively). In addition, the optimal oxynitriding/DLC duplex coating possessed the lowest corrosion current (Icorr = 2.66 × 10-6 A•cm-2) and highest polarization resistance (Rp = 1.57 × 104 Ω•cm2) in 3.5 wt% NaCl solutions. These results confirmed that the optimal wear and corrosion resistance followed the oxynitriding/DLC duplex treatment.

並列關鍵字

SKD11 Tool Steel ； Oxynitriding Treatment ； DLC ； DC-pulsed PECVD ； Bipolar-pulsed ； Wear.

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