TA15合金表面Cr-Si合金层的高温氧化及抗热腐蚀行为研究

发布时间：2018-01-08 19:21

本文关键词：TA15合金表面Cr-Si合金层的高温氧化及抗热腐蚀行为研究　出处：《南京航空航天大学》2016年硕士论文　论文类型：学位论文

【摘要】：TA15合金兼具α合金优异的抗蠕变性能、良好的耐蚀性及(α+β)合金的高强度,其独特的优势,使其成为航空航天领域具有巨大潜力的新型高温结构材料。但其抗高温氧化性能和抗热腐蚀性能的不足,严重限制了该合金的使用范围。为解决这一问题,采用双层辉光等离子表面冶金技术在TA15合金表面制备Cr-Si合金层,以提高其抗高温氧化及抗热腐蚀性能。TA15合金基体表面成功渗Cr后,再进行渗Si,渗Cr的最佳工艺参数为:温度950℃,源极电压950V;工件电压400V;工作气压35Pa;极间距15mm;保温时间3h。渗Si层的最佳工艺参数为:温度1000℃,源极电压1000V;工件电压450V;工作气压38Pa;极间距15mm;保温时间3.5h。利用SEM、EDS、XRD对Cr-Si合金层的表面形貌、截面形貌、元素分布及相组成进行分析,结果表明:Cr-Si合金层表面均匀致密,无孔洞、缝隙;表面相组成为Cr、Si和Cr3Si;厚度约为40μm,与基体之间结合力达63.5N。对基体及Cr-Si合金层在不同温度下进行高温氧化实验,结果表明:温度低于750℃时,基体及Cr-Si合金层都具有一定抗高温氧化能力,基体在800℃以上失去抗氧化能力;Cr-Si合金层在850℃氧化50h后,表面出现轻微剥落,但仍具有较好的抗高温氧化作用。对基体及Cr-Si合金层在750℃不同时间进行高温氧化实验,结果表明:基体表面氧化膜呈Al_2O_3和TiO_2交替分层分布;Cr-Si合金层表面能迅速生成Cr2O3和SiO_2保护膜,起到较好抗高温氧化作用。对基体及Cr-Si合金层在不同温度Na_2SO_4盐中热腐蚀实验,结果表明:Cr-Si合金层增重小于基体,且温度低于750℃热腐蚀100h时均表现出一定的抗热腐蚀能力。基体在800℃氧化50h时,氧化膜腐蚀剥落;Cr-Si合金层在800℃中热腐蚀100h后,仍能起到较好的抗热腐蚀作用。对基体及Cr-Si合金层在700℃的Na_2SO_4盐中不同时间热腐蚀实验,结果表明:基体及Cr-Si合金层均表现出一定的抗热腐蚀能力;Na_2SO_4盐可使氧化膜疏松多孔,还能与金属元素发生氧化或硫化反应,是加速氧化腐蚀的催化剂。对基体及Cr-Si合金层在75%Na_2SO_4+25%NaCl混合盐中不同时间热腐蚀试验,结果表明:基体在混合盐中抗热腐蚀能力急剧下降,生成的氧化膜疏松,且易与基体剥离;Cr-Si合金层表面氧化膜仍具有较好的抗热腐蚀能力。氯离子的存在加速了热腐蚀进程,故混合盐中的热腐蚀过程是氧化、硫化和氯化的综合过程。
[Abstract]:TA15 alloy with alpha alloy excellent creep resistance, corrosion resistance and good (alpha + beta) high strength alloy, its unique advantages, make it become the new high temperature structural materials with great potential in aerospace field. But the high temperature oxidation resistance and corrosion resistance is not enough, seriously limits the use of the scope of this alloy. In order to solve this problem, on the surface of TA15 alloy Cr-Si alloy prepared by layer by double glow plasma surface metallurgy technology, in order to improve its resistance to high temperature oxidation and hot corrosion resistance of.TA15 alloy surface infiltration success after Cr, then the Si penetration, the optimum process parameters of Cr infiltration were temperature 950 DEG C, the source voltage 950V; workpiece voltage 400V working pressure; 35Pa; electrode spacing 15mm; optimum parameters of the heat preservation time is 3h. infiltration Si layer: 1000 degrees Celsius temperature, source voltage 1000V; workpiece voltage 450V working pressure; 38Pa; electrode spacing 15mm; holding time 3.5H . using SEM, EDS, XRD on the surface morphology of Cr-Si alloy layer cross section morphology, element distribution and phase composition were analyzed, the results show that the Cr-Si alloy layer on the surface is uniform and dense, no holes, cracks; the surface is Cr, Si and Cr3Si; the thickness is about 40 m, and the matrix between the combination of up to 63.5N. on the matrix and Cr-Si alloy layer under different temperature by high temperature oxidation experiments, the results show that the temperature is lower than 750 DEG C, and Cr-Si matrix alloy layer has a certain resistance to oxidation at high temperature, the base lose antioxidant ability in more than 800 DEG C; Cr-Si alloy layer at 850 DEG 50h after oxidation, slight surface spalling, but still has good resistance to high temperature oxidation of Cr-Si alloy layer and the matrix. 750 degrees in the different time of high temperature oxidation experiments, the results show that the oxide film on the substrate surface is Al_2O_3 and TiO_2 alternate layer distribution; surface layer of Cr-Si alloy can quickly generate Cr2O3 and SiO_2 The protective film, play a better role. High temperature oxidation resistance of substrate and Cr-Si alloy layer at different temperature Na_2SO_4 salt in hot corrosion experiments, the results show that the Cr-Si alloy layer is less than the weight matrix, and the temperature is lower than 750 DEG C hot corrosion of 100h showed certain ability of corrosion resistance. The matrix at 800 DEG 50h oxidation. The film corrosion spalling; Cr-Si alloy layer at 800 DEG C in hot corrosion of 100h, still can play a better role. Corrosion resistance of different time of hot corrosion experiment, and Cr-Si matrix alloy layer at 700 DEG Na_2SO_4 salt results show that matrix and Cr-Si alloy showed certain ability of corrosion resistance; salt Na_2SO_4 the film is loose and porous, but also with metal elements or sulfide oxidation reaction is the catalyst of oxidation corrosion. The matrix and Cr-Si alloy layer in 75%Na_2SO_4+25%NaCl mixed salt in different time hot corrosion test results Matrix: thermal in the mixed salt corrosion ability decreased dramatically, the film is loose and easy to generate, and the matrix of Cr-Si alloy layer peeling; surface oxide film still has better ability of corrosion resistance. The presence of chloride ions accelerated the hot corrosion process, the hot corrosion process in the mixed salt is the oxidation process of sulfide and chloride synthesis.

【学位授予单位】：南京航空航天大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TG174.4

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