Oxidation and hot corrosion behavior of Ti2AlNb-based alloy with and without enamel coating at 800℃

The oxidation and hot corrosion behavior of Ti2AlNb-based alloy with and without enamel coating at 800℃was investigated. The results indicated that Ti-22Al-25Nb alloy exhibited poor oxidation resistance at 800℃. The constitution of oxide scale had the effect on its oxidation rate. Because of the S and Cl accelerating the corrosion process, Ti-22Al-25Nb alloy suffered severe hot corrosion and exhibited very poor hot corrosion resistance. Enamel coating could remarkably improve the high temperature oxidation resistance of Ti-22Al-25Nb alloy because it had good chemical stability and matched thermal expansion coefficient with the substrate. In (Na,K)2SO4+NaCl molten salts at 800℃, chemical reactions between molten salts and enamel coating occurred and complicated products formed on the surface of the enamel coating; Cl- in the molten salts could penetrate through the coating and induced the substrate corrosion, but enamel coating still had good hot corrosion resistance.

Effect of Sputtered TiAlCr Coatings on Oxidation and Hot Corrosion Resistance of Ti-24Al-14Nb-3V

The effect of sputtered Ti-50Al-10Cr and Ti-50A1-20Cr coatings on both isothermal and cyclic oxidation resistance at 800-900℃ and hot corrosion resistance at 850℃ of Ti-24Al-14Nb-3V was investigated. Results indicated that Ti-24Al-14Nb-3V alloys exhibited poor oxidation resistance due to the formation of Al2O3+TiO2+AlNbO4 mixed scales in air at 800-900℃ and poor hot corrosion resistance due to the spoliation of scales formed in Na2SO4+K2SO4 melts at 850℃. Both Ti-50Al-10Cr and Ti-50Al-20Cr coatings remarkably improved the oxidation and hot corrosion resistance of Ti-24Al-14Nb-3V alloy.

Oxidation and Hot Corrosion Behavior of a Composite Coating System

The oxidation and hot corrosion behavior of Co-Ni-Cr-AI-Ta-Y coating produced by magnetron sputtering with and without enamel coating has been investigated in air at 900℃ and in molten 75 wt pct NaCl+25 wt pct Na2SO4 at 850℃. The results show that the enamel coating possesses good hot corrosion resistance in the molten salts, in comparison with the sputtered Co-Ni-Cr-AI-Ta-Y coating. In the hot corrosion test, breakaway corrosion did not occur on the samples with enamel coating and the composition of enamel coating did not significantly change either. The oxidation resistance of the sputtered coating, which offers good adhesion, can be improved by the enamel coating.

搪瓷涂层对Ti-24Al-14Nb-3V抗氧化及热腐蚀性能的影响

研究了搪瓷涂层对 Ｔｉ－２４Ａｌ－１４Ｎｂ－３Ｖ抗高温氧化及热腐蚀性能的影响结果表明，在 ９００ ℃下，由于搪瓷涂层具有较高的化学稳定性，且和 Ｔｉ－２４Ａｌ－１４Ｎｂ-３Ｖ有比较接近的热膨胀系数，大大 改善了 Ｔｉ－２４Ａｌ－１４Ｎｂ－３Ｖ抗恒温氧化及循环氧化性能在 ８５０ ℃（Ｎａ， Ｋ）２ＳＯ４中，虽然熔盐中的 Ｎａ＋与搪瓷涂层中的 Ｃａ２＋进行离子交换引起搪瓷涂层少量减重，但它仍具有优异的抗熔融硫酸盐腐蚀 能力在８５０℃ＮａＣｌ＋Ｎａ２ＳＯ４中，搪瓷涂层对Ｔｉ－２４Ａｌ－１４Ｎｂ－３Ｖ具有一定的保护作用，但是由 于熔盐中的 Ｎａ＋与搪瓷涂层中的 Ｃａ２＋进行离子交换，和熔盐中的 Ｃｌ－对搪瓷涂层的腐蚀作用及对基 材的点蚀作用，使其保护作用下降。

搪瓷/NiCrAlY复合涂层的抗高温氧化及热腐蚀行为

研究了溅射NiCrAlY及搪瓷/NiCrAlY复合涂层在900℃空气氧化及850℃75mass%Na2SO4+25mass%K2SO4和75mass%Na2SO4+25mass%NaCl的热腐蚀行为.结果表明:溅射NiCrAlY涂层900℃表面生成了单一的氧化铝膜,具有良好的抗氧化性能,而搪瓷复合涂层进一步提高了NiCrAlY层的抗氧化性能;850℃两种盐的热腐蚀表明,基体合金没有出现内氧化及内硫化现象,搪瓷层的成分也没有显著变化,表现出优异的抗热腐蚀性能.

Al-Si共渗涂层对M951合金高温氧化和热腐蚀的影响

采用料浆法在镍基高温合金。M951上制备Al-Si共渗涂层,研究了合金及涂层样品在1100℃恒温、循环氧化及在850℃在Na_2SO_4+25%K_2SO_4和Na_2SO_4+25%NaCl两种混盐中的热腐蚀行为。同时利用SEM、EDS对氧化膜表截面形貌进行了观察,并结合X射线衍射对相组成进行了分析。结果表明,在1100℃恒温及循环氧化时,M951合金表面生成NiO、NiAl_2O_4、Nb_2O_5及A1_2O_3等的混合氧化物膜,氧化膜不均匀且剥落严重。在Al-Si涂层样品表面形成稳态的α-A1_2O_3,大幅度提高了合金的抗高温氧化性能。在850℃热腐蚀试验中,M951合金40 h后发生灾难性腐蚀,而Al-Si涂层经100 h腐蚀后仍保持完整,表面形成极薄且连续的θ-A1_2O_3氧化膜,大幅度提高了合金的抗热腐蚀性能。

搪瓷涂层700℃长期抗高温氧化和热腐蚀行为研究

研究了在钛铝金属间化合物上涂覆的一种20~40μm厚的新型搪瓷涂层在700℃条件下1000 h高温氧化和硫酸盐+Na Cl热腐蚀600 h的高温腐蚀行为。结果表明,搪瓷涂层具有很高的高温稳定性,在长时间的实验中有效地避免了基体的高温腐蚀,涂层未出现开裂或剥落。在涂层制备过程和高温腐蚀测试过程中,在涂层/基体界面发生了界面反应,形成了由α-Al2O3、Ti O2、Al2Si O5和Al2Ti O5组成的薄氧化物层。

溅射AlY涂层对Ni基合金抗热腐蚀性能的影响

采用磁控溅射方法在镍基合金表面制备AlY涂层,并对涂层试样分别进行预氧化和真空扩散退火处理,对比研究镍基合金、预氧化AlY涂层试样和真空扩散退火AlY涂层试样在900℃硫酸盐膜下的热腐蚀动力学及腐蚀产物的组成。结果表明,各试样的腐蚀动力学均分段遵循抛物线规律。对于24 h的腐蚀增重,涂层试样明显小于镍基合金,预氧化试样略低于真空扩散退火试样。镍基合金腐蚀膜分层且开裂,外层主要是Cr_2O_3及NiO的混合物,其下有不连续的Al_2O_3;真空扩散退火试样的腐蚀膜外层是连续的Al_2O_3,其下是Cr和Ni的氧化物,再下是连续的Y_2O_3;预氧化试样形成了与真空扩散退火试样相似的腐蚀膜,但略薄于真空扩散退火Al Y涂层试样。表面连续Al_2O_3膜及连续的Y_2O_3层的形成,提高了腐蚀膜的保护性和粘附性,不同方法处理的AlY涂层提高了镍基合金的抗热腐蚀性能。

DD98M纳米晶AlSi渗层制备及抗高温腐蚀性能研究

采用磁控溅射技术在DD98M合金表面制备了同成份的纳米晶,采用多弧离子镀技术在DD98M纳米晶涂层表面沉积了AlSi涂层,对上述制备态纳米晶+AlSi复合涂层进行了真空扩散处理,得到了外层为β-NiAl层、内层为γ'-Ni_3Al层的双层结构复合涂层。研究了合金、DD98M纳米晶涂层及复合涂层在1050℃恒温氧化及900℃下Na_2SO_4+25%K_2SO_4混合熔盐体系中的热腐蚀行为。结果表明:1050℃恒温氧化时,DD98M合金表面生成NiO,α-Al_2O_3,Ta_(0.8)O_2,CrTaO_4及NiAl_2O_4等组成的混合氧化物膜,氧化膜开裂剥落严重。纳米晶涂层表面生成α-Al_2O_3和少量NiAl_2O_4组成的混合氧化物膜,复合涂层表面形成了均匀致密的单一α-Al_2O_3膜。纳米晶涂层和复合涂层大幅提高了合金的抗恒温氧化性能。在900℃下Na_2SO_4+25%K_2SO_4熔盐中,DD98M合金20 h后即发生了灾难性腐蚀,沉积态纳米晶及其预氧化涂层提高了合金的抗热腐蚀性能,复合涂层大幅提高了合金的抗热腐蚀性能。