鎳-鈦熔射塗層之耐蝕與磨潤性能研究

Study on Wear and Corrosion Resistances of Thermal Sprayed Ni-Ti Composite Coatings

張家華(CHIA-HUA CHANG)

指導教授 ： 鄭銘章

國立中央大學/工學院/機械工程學系/博士(2012年)

摘要

金屬熔射為一種常見的鋼鐵材防蝕與硬面技術，金屬熔射法依熱源與材料的不同可區分為火焰線材(粉末)熔射法、電漿熔射法、電弧熔射法(arc spraying)、塑膠熔射及高速燃氣熔射法等(High Velocity Oxygen Fuel, HVOF)。相較於火焰熔射法，因電弧熔射法具有高堆疊率、高附著力與較低孔隙率，廣泛地應用於鋼鐵材防蝕、石化、汽車、模具與航太工業。燃氣速度可達600～2400米/秒的高速燃氣熔射法(HVOF)使熔射塗層的緻密性、氧化程度及附著力均獲得大幅改善，使熔射塗層可以應用於更嚴苛的作業環境。
本文旨在探討以熔射法製備鎳-鈦複合塗層之方法，並就塗層表面特性、微結構、磨潤特性與耐蝕性進行討論，論文第一部分以電弧熔射法製備鎳-鈦複合塗層，其中熔射鎳-鈦塗層係由二條同步進給之鎳線與鈦線經引弧、霧化後沉積於AISI 1020基材上形成。第二部分分別以化學鍍及噴霧乾燥法製備熔射用鎳-鈦複合粉末，以鈦粉末為核化學鍍鎳為殼之複合粉末，分為低鈦含量與高鈦含量二種，分別標記為Ni-Ti10與Ni-Ti30，奈米團聚之鎳鈦複合粉末則記為nano Ni-Ti。自製之鎳-鈦複合粉末再以高速燃氣熔射法製備塗層。熔射鎳-鈦塗層分別進行SEM/EDS，XRD及DTA分析，以探討熔射塗層表面性質，並利用電化學交流阻抗法與動電位極化曲線法進行鎳-鈦熔射塗層耐蝕性評估。磨潤試驗分別依ASTM D6425-99及ASTM G99規範進行磨耗試驗，以評估塗層的耐磨性能。
由電弧熔射複合塗層表面特性檢測結果顯示，以電弧熔射法成功地製備以鎳及鈦為基底，鎳-鈦合金及鎳-鈦介金屬為分散相的複合塗層。三組電弧熔射參數中以高電弧電流及電壓下(32V, 300A)較易形成介金屬相。複合塗層電化學實驗顯示鎳-鈦熔射複合塗層耐蝕性能主要受到熔射層組織與膜厚影響，熔射鎳的引入，改善了單一熔射鈦塗層微裂紋的缺陷，進而提升熔射鈦塗層的耐蝕性。磨潤實驗結果則顯示鈦金屬的引入，可大幅提升單一熔射鎳層的耐磨性能，相較於火焰熔射鎳塗層，耐磨性能提高了586倍之多。
由高速燃氣熔射複合塗層表面特性檢測結果顯示，以高速燃氣熔射法製備之塗層較電弧熔射法緻密。由XRD及DTA分析結果顯示，三種高速燃氣熔射塗層中以化學鍍鎳鈦複合粉末製備之塗層(Ni-Ti10與Ni-Ti30)，含有鎳-鈦合金及鎳-鈦介金屬，以奈米團聚鎳鈦複合粉末製備之塗層(nano Ni-Ti)，則無明確鎳-鈦合金及鎳-鈦介金屬發現。複合塗層耐蝕性實驗顯示，以高速燃氣熔射法製備之鎳-鈦複合塗層較電弧熔射法緻密，耐蝕性優於電弧熔射塗層。三種高速燃氣熔射塗層中以奈米鎳-鈦複合塗層較為緻密，耐蝕性亦最佳。三種高速燃氣熔射塗層之磨耗實驗結果顯示，以高速燃氣熔射法製備之鎳-鈦複合塗層較為均勻，磨耗實驗結果較為一致，三種高速燃氣熔射塗層中以高鈦含量之鎳-鈦複合塗層(Ni-Ti30)具有較佳耐磨性能。高速燃氣熔射法製備塗層之耐蝕性與耐磨性普遍優於電弧熔射法。

關鍵字

熔射 ； 耐腐蝕 ； 磨潤 ； 鎳-鈦

並列摘要

Thermal spraying is a well-developed coating technique in which metallic or non-metallic materials are melted and softened by either chemical or electrical energy and the molten droplets are subsequently atomized and impacted on a prepared substrate to develop a laminar coating.
In this study, we investigated the corrosion and wear performance of Ni-Ti composite coatings with distinct parameters and thermal spraing technology. In the first part, the coatings were prepared by arc spraying with the Ti and Ni wires fed synchronously. In the second part, we investigated Ni-Ti composite coatings deposited on AISI 1020 steel via HVOF spraying. The feedstock powders were prepared by either electro less plating (Ti powder clad with Ni) or spray drying (agglomeration of nanoscale Ni and Ti powders). We performed structural, surface morphological, and compositional analyses of the Ni-Ti composite coatings using microhardness, SEM/EDS, XRD, and DTA analysis. Electrochemical AC impedance and potentiodynamic polarization tests were carried out to examine the anti-corrosion performance of the coating. Ball-on-disc dry wear tests based on the ASTM G99 and ASTM D6425-99 standard were performed at room temperature to evaluate the anti-wear properties.
We found some intermetallic compounds such as TiNi3 and Ni-Ti alloy within the arc sprayed Ni-Ti composite coating. The wear resistance of the arc sprayed Ni-Ti composite coating is much better than that of the Ni-sprayed coating but slightly worse than that of the Ti-sprayed coating. The corrosion resistance of the arc-sprayed Ni-Ti coating is superior to that of Ti but worse than that of Ni. The corrosion and wear performance of the composite coating are greatly influenced by the coating microstructure and thickness.
The coating characterization tests of HVOF Ni-Ti coating indicated that Ni-Ti intermetallic compounds such as Ti3Ni4 were only found inside the Ni-Ti coatings with a high Ti content. The HVOF Ni-Ti coating prepared by agglomerated Ni-Ti nanopowder was oxidized to a greater degree than the other specimens. The AC impedance and potentiodynamic polarization test results showed that the Ni-Ti nanopowder exhibited the best corrosion resistance among the three Ni-Ti coatings. The wear test results indicated that the Ni-Ti 30 coating with its higher Ti content exhibited a better wear resistance than the other two. In general, the HVOF Ni-Ti composite coatings exhibited a better wear and corrosion resistance than those of arc spraying.

並列關鍵字

Thermal spraying ； Ni-Ti ； Wear ； Corrosion

參考文獻

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