Ti基与Cr基氮化物涂层的抗氧化性能

Oxidation resistance of Ti-based and Cr-based nitride coatings

选用TiN,TiAlN,CrN和CrAlN 4种涂层材料,使用电阻炉对试样加热并保温,进行抗氧化性能实验,利用SEM、EDS和XRD获得了氧化结果。结果表明:Ti基涂层的氧化机制以O原子向涂层内部扩散为主;Cr基涂层的抗氧化机制为N原子和Cr离子向涂层表面的扩散所形成的微孔诱发的氧化;Cr基涂层比Ti基涂层具有较好的抗氧化性;Al的加入使得TiAlN与CrAlN涂层的氧化性能和高温后硬度提高,特别是CrAlN氧化后生成的致密Cr2O3和Al2O3混合氧化物使其抗氧化性能达到最优;氧化及涂层与基体的热涨失配使得几类涂层最终开裂失效;四种涂层的抗氧化能力为CrAlN>TiAlN>CrN>TiN。

Four kinds of hard coatings, TiN, TiA1N, CrN and CrA1N were heat-treated in electric furnace to make oxidation experiment. The oxidation mechanisms of the four coatings were studied by means of SEM, EDS and XRD. The results show that the oxidation mechanism of Ti-based coating is mainly controlled by the diffusion of oxygen atom to coating inner, but for Cr-based coatings, oxidation is caused by micro-holes which are formed by diffusion of nitrogen atom and chromium ion to coating surface. The Cr-based coatings exhibit evidently better oxidation resistance than Ti-based coatings. Oxidation resistance and hardness of TiA1N and CrA1N coatings at elevated temperatures are improved by addition of A1 and the dense oxides of Cr203 and A1203 make CrA1N coating present the best oxidation resistance among them. Oxidation and the mismatch of expansion coefficients between coatings and substrate are responsible for cracking and failure of the coatings. The oxidation resistance comparison of the four kinds of coatings is as follows ： CrAIN 〉 TiAIN 〉 CrN 〉 TiN.