等离子渗镀CrON复合涂层结构与抗铝液熔蚀性能

Microstructure and Corrosion Behavior of Duplex CrON Coatings in Molten Aluminum

摘要:

采用等离子渗氮/电弧离子镀复合方法在H13模具钢表面制备出CrON涂层，研究氧流量对CrON复合涂层结构及抗铝液熔蚀性能的影响。结果表明，随着氧流量的增加，所制备的涂层主要物相由氮化物向氧化物转变，在氧流量较低时主要呈现面心立方CrN结构，而在氧流量为200 mL/min时制备的涂层形成典型的Cr₂O₃晶体相特征。掺入适量的氧，CrN涂层柱状晶生长受到抑制，涂层结构更加致密。涂层表面缺陷和粗糙度随着氧含量的增加而增大。CrON复合涂层在铝液中的失效形式是局部点蚀。由于形成致密的结构和良好的热稳定性，在氧流量为50 mL/min时制备的涂层具有优异的抗铝液熔蚀能力，而氧流量较高时表面生成致密的Cr₂O₃抗氧化层也有利于提高抗铝液熔蚀性能。

Abstract:

The duplex CrON coatings were prepared on H13 tool steels by combination of plasma nitriding and arc ion plating. The effects of oxygen flow rate on microstructure and corrosion behavior of duplex CrON coating in the molten aluminum were investigated. Results show that the as-deposited coatings with oxygen flow rate of 0, 50, and 100 mL/min, namely CrON-0, CrON-50, and CrON-100 coatings, mainly consist of B1-CrN phase. The major components of CrON coating change from nitride into oxide phase with increasing the oxygen flow rate, and the Cr₂O₃ crystalline phase is obviously observed in the as-deposited coatings with oxygen flow rate of 200 mL/min, namely CrON-200 coating. Oxygen addition in nitride restrains the columnar growth of grains resulting in the dense microstructure. The surface defects and roughness increase with the increase of oxygen content. The failure behavior of duplex CrON coatings is mainly corrosion pitting in molten aluminium. The CrON-50 coating reveals the best corrosion resistance due to the dense columnar microstructure and high thermal stability. The dense Cr₂O₃ layer in CrON-200 coating is also favourable for corrosion protection against the molten aluminum.