在NaAlO2溶液中,采用微等离子氧化法在Ti-6Al-4V合金表面制备出含α-Al2O3相高硬度陶瓷膜。利用显微硬度计分析了膜层的硬度及其分布,用落球冲击法、耐热循环冲击法研究了膜层与基体的界面结合情况,并探讨了在微等离子体氧化过程中电解液浓度和负相/正相电流比(Ic/Ia)对膜层相组成和力学性能的影响规律。结果表明:在浓度较高的铝酸钠溶液中(0.15-0.20mol/L)得到的膜层含有大量α-Al2O3相且随着Ic/Ia比例减小α-Al2O3相的含量增加,此种膜层硬度为1100-1600Hk50g;而在低浓度溶液中(≤0.050mol/L)得到的膜层只含有Al2TiO5和金红石型TiO2,硬度仅为500-850Hk50g。横截面硬度分布:从界面处到膜的表层硬度逐渐增大并在达到最大值后缓慢下降。利用SEM观察了经落球冲击后膜层的表面的状态,发现膜层表面无裂纹及脱落的现象,膜层与基体结合良好。另外,在耐热循环冲击试验中厚度最低的膜层热冲击循环次数最高。
Ceramic coatings containing α-Al2O3 were prepared on Ti-6Al-4V alloy by an alternat-ing-current micro-plasma oxidation (MPO) method in
solutions of sodium aluminate. The Knoop hardness (HK) and coating-substrate adhesion of MPO coatings were measured by the microhardness tester and
ball-on-plate impact tester. Influences of the electrolyte concentration and cathodic to anodic current ratio Ic/Ia on the phase
composition and mechanical properties of coatings were discussed. The results show that the coating formed at weak aluminate solution
(≤0.05mol/L) consists of TiO2 and Al2TiO5; at high aluminate concentration (0.15-0.20mol/L) consists of TiO2, Al_2TiO5 and
α-Al_2O_3. The content of α-Al2O3 increases with the decreasing Ic/Ia ratio. HK of coatings containing α-Al2O3 varies within 1100-1600 Hk50g which
is much higher than that of Ti substrate and even the coating not containing α-Al2O3. Distribution profile of HK from
interface toward the coating surface shows that HK gradually increases and reaches the maximum value around 35--45μm. In addition, there is no spallation
after impact tests observed by SEM, which indicates MPO coatings have the excellent interfacial adhesion with the titanium substrate. The
cycle thermal shock tests show that, the thinnest film possesses the highest number of cycles.
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