航空发动机高温固体润滑涂层材料的制备与性能研究

发布时间：2018-04-28 01:49

本文选题：NiCoCrAlY-Cr_2O_3-Ag + 涂层　；参考：《中国科学院大学(中国科学院过程工程研究所)》2017年博士论文

【摘要】：目前先进航空发动机的高压压气机和低压涡轮部位采用刷式封严结构,由于刷式封严的主要部件刷丝需要在高温燃气条件下与高速运转的转子轴表面摩擦接触,因此为了降低刷丝与转子轴表面的磨损,通常利用热喷涂技术在转子轴表面制备一层高温自润滑耐磨涂层。由于使役环境恶劣,该涂层不仅要具有宽温域自润滑减摩耐磨效果,还应该具备良好的高温抗氧化、耐熔盐腐蚀、耐热循环等性能。本论文采用化学还原、化学镀、离心喷雾造粒以及固态合金化技术制备了 Ag、Ag-Mo、CoNiCrAlY-Cr_2O_3以及NiCoCrAlY-Cr_2O_3四种粉体,并采用等离子喷涂技术制备了 CoNiCrAlY-Cr_2O_3、NiCoCrAlY-Cr_2O_3、NiCoCrAlY-Cr_2O_3-Ag 以及 NiCoCrAlY-Cr_2O_3-AgMo 四种复合涂层,对复合涂层的结构以及性能进行了系统研究,揭示了复合涂层在苛刻环境条件下的结构与性能变化规律及相关作用机理。主要研究内容和结果如下:(1)对等离子喷涂CoNiCrAlY-Cr_2O_3和NiCoCrAlY-Cr_2O_3复合涂层的摩擦磨损性能、抗氧化性和抗熔盐腐蚀性能进行了研究。摩擦磨损结果表明:随着温度的上升,两种涂层的摩擦系数均呈下降趋势。600℃以下,CoNiCrAlY-Cr_2O_3涂层的摩擦系数略低于NiCoCrAlY-Cr_2O_3涂层;600℃以上,两种涂层的摩擦系数相差不大。涂层的磨损量均在10-5mm~3/Nm数量级。涂层的氧化实验表明:在800℃下,NiCoCrAlY-Cr_2O_3涂层的抗氧化性略优于CoNiCrAlY-Cr_2O_3涂层。对两种涂层进行氧化动力学分析,其氧化动力学曲线分为大斜率直线、抛物线和小斜率直线三个阶段,涂层均具有较好的抗氧化性能。氧化后表面生成的尖晶石氧化物以及涂层中沉积的Cr_2O_3对涂层起到了保护作用。熔盐腐蚀实验表明:由于Co·Co_3S_2 比Ni·Ni_3S_2共晶体在800℃下相对稳定,并且Co基合金具有更好的耐S腐蚀性能,因此CoNiCrAlY-Cr_2O_3涂层的抗熔盐腐蚀性能优于NiCoCrAlY-Cr_2O_3涂层。(2)研究了 Ag膜在硬质基体表面的润滑性能,发现Ag膜在常温下的摩擦系数仅有0.2。以Ag为润滑剂,采用等离子喷涂技术制备了 NiCoCrAlY-Cr_2O_3、NiCoCrAlY-Cr_2O_3-10Ag以及NiCoCrAlY-Cr_2O_3-30Ag三种复合涂层,涂层结构致密,孔隙率都在2.5%左右。NiCoCrAlY-Cr_2O_3涂层的显微硬度约为650HV0.2。随着Ag的加入,涂层的显微硬度降低,但是结合强度有所提高。NiCoCrAlY-Cr_2O_3-30Ag涂层的结合强度达到53MPa,比NiCoCrAlY-Cr_2O_3提高了 17MPa。涂层的摩擦磨损性能表明:与NiCoCrAlY-Cr_2O_3涂层相比,加入10%Ag后,涂层的摩擦系数从室温到800℃有所降低,在600℃达到最低值0.3。当加入30%Ag时,涂层在高温下的摩擦系数和磨损量都显著增高。摩擦机理分析表明:低温下,Ag在涂层表面铺展成膜发挥润滑作用;高温下,Ag扩散到表面并发生熔融软化,过量的Ag造成涂层严重的黏着磨损和塑性变形。涂层的热循环及氧化实验表明:加入Ag后,涂层的抗热震性能提高,但是氧化增重略高于NiCoCrAlY-Cr_2O_3涂层。(3)以Ag-Mo作为复合固体润滑剂,采用等离子喷涂制备了NiCoCrAlY-Cr_2O_3-10AgMo 和 NiCoCrAlY-Cr203-15AgMo 两种复合涂层。两种涂层的显微硬度均约为600HV0.2。涂层的结合强度分别为42±2MPa以及45±5MPa。涂层的摩擦磨损性能表明:加入Ag-Mo复合固体润滑剂的涂层从室温到800℃内具有优异的润滑性能,在800℃摩擦系数仅有0.3左右。磨损量从室温到800℃都保持在10-5mm~3/Nm数量级。600℃以上,摩擦表面生成的NiMoO_4和Ag_2MoO_4化合物有效降低了涂层的摩擦磨损。此外,较高的载荷会促进Ag,Mo与O_2反应生成Ag_2MoO_4润滑膜的过程,并有助于压实磨屑形成保护性釉质层,提高涂层润滑耐磨性能。(4)用冷等静压和高温烧结法制备了 Ag-Mo复合材料,测试并分析了材料的摩擦磨损性能和润滑机理。结果发现:低温下,铺展在摩擦表面的Ag膜起到润滑作用;高温下摩擦表面生成的一系列低熔点钼酸银化合物降低了涂层的摩擦磨损。通过对Ag-Mo-O_2固相反应机理的研究,建立了 Ag-Mo-O_2三元体系生成Ag_2MoO_4的固相反应模型。研究发现:Ag_2MoO_4在空气气氛下1000℃以内不分解也不挥发,并且对NiCoCrAlY-Cr_2O_3涂层具有良好的润湿性。(5)有限元模拟计算表明:涂层的弹性模量越高,封严层与粘结层之间的应力梯度越大,在热循环过程中封严涂层越容易产生裂纹并脱落。在涂层中加入Ag可使弹性模量降低34%,改善涂层与基体热膨胀系数的匹配性,从而提高涂层的抗热震性能。
[Abstract]:At present, the high pressure compressor and the low pressure turbine part of Advanced Aero engine use a brush seal structure. Because the brush seal is the main part of the brush, the brush wire needs to contact with the surface of the rotor shaft running at high speed under the condition of high temperature gas. So in order to reduce the wear of the brush and the rotor shaft, the thermal spraying technology is usually used in the rotor shaft. A layer of high temperature self lubricating and wear-resistant coating is prepared on the surface. Due to the bad environment, the coating should not only have the effect of self lubrication and wear resistance in the wide temperature field, but also have good antioxidation, corrosion resistance and heat-resistant cycle. This paper is prepared by chemical reduction, electroless plating, centrifugal spray granulation and solid-state alloying technology. Four kinds of powders of Ag, Ag-Mo, CoNiCrAlY-Cr_2O_3 and NiCoCrAlY-Cr_2O_3 were used to prepare four kinds of composite coatings, CoNiCrAlY-Cr_2O_3, NiCoCrAlY-Cr_2O_3, NiCoCrAlY-Cr_2O_3-Ag and NiCoCrAlY-Cr_2O_3-AgMo. The structure and properties of the composite coatings were systematically studied. The main contents and results are as follows: (1) the friction and wear properties of the plasma sprayed CoNiCrAlY-Cr_2O_3 and NiCoCrAlY-Cr_2O_3 composite coatings, the oxidation resistance and the corrosion resistance of the molten salt were studied. The friction and wear results showed that with the increase of temperature, two The friction coefficient of the coating is below.600 C, and the friction coefficient of the CoNiCrAlY-Cr_2O_3 coating is slightly lower than that of the NiCoCrAlY-Cr_2O_3 coating; the friction coefficient of the two kinds of coatings is not quite different at 600 degrees C. The wear amount of the coating is at the order of 10-5mm~3/Nm. The oxidation test of the coating shows that the oxygen resistance of the NiCoCrAlY-Cr_2O_3 coating at 800 C The oxidation kinetics of two kinds of coatings was analyzed. The kinetic curves of the two coatings were divided into three stages: large slope straight line, parabolic line and small slope straight line. The coating had better oxidation resistance. The oxidation of the spinel formed on the surface after oxidation and the deposited Cr_2O_3 in the coating played a role in the coating. The corrosion test of molten salt showed that Co. Co_3S_2 was relatively stable at 800 C than Ni Ni_3S_2 eutectic, and Co based alloy had better corrosion resistance to S. Therefore, the corrosion resistance of CoNiCrAlY-Cr_2O_3 coating was better than that of NiCoCrAlY-Cr_2O_3 coating. (2) the lubrication performance of Ag film on the surface of hard matrix was studied, and Ag was found to find Ag. The friction coefficient of the film at normal temperature is only 0.2. Ag as lubricant. Three kinds of composite coatings, NiCoCrAlY-Cr_2O_3, NiCoCrAlY-Cr_2O_3-10Ag and NiCoCrAlY-Cr_2O_3-30Ag, are prepared by plasma spraying technology. The coating structure is compact and the porosity of the coating is about 2.5%.NiCoCrAlY-Cr_2O_3 coating with the addition of 650HV0.2. with Ag. The microhardness of the coating is reduced, but the bonding strength of the.NiCoCrAlY-Cr_2O_3-30Ag coating is up to 53MPa, and the friction and wear performance of the 17MPa. coating is increased than that of NiCoCrAlY-Cr_2O_3. Compared with the NiCoCrAlY-Cr_2O_3 coating, the friction coefficient of the coating decreases from room temperature to 800 C after adding 10%Ag, and the friction coefficient is reached at 600. When the minimum value of 0.3. is added to 30%Ag, the friction coefficient and wear amount of the coating increase significantly at high temperature. The analysis of the friction mechanism shows that at low temperature, the Ag spread into the coating surface to play the lubrication; at the high temperature, the Ag diffuses to the surface and melts and softens, and the excessive Ag causes the coating's serious adhesion and plastic deformation. The thermal evidence-based of the coating. The experiments of ring and oxidation show that the thermal shock resistance of the coating is increased after adding Ag, but the oxidation weight gain is slightly higher than that of the NiCoCrAlY-Cr_2O_3 coating. (3) two composite coatings of NiCoCrAlY-Cr_2O_3-10AgMo and NiCoCrAlY-Cr203-15AgMo are prepared by plasma spraying with Ag-Mo as a composite lubricant. The microhardness of the two kinds of coatings is about 600H The friction and wear properties of the V0.2. coating with the bonding strength of 42 + 2MPa and 45 + 5MPa. coatings show that the coating with Ag-Mo composite solid lubricants has excellent lubrication performance from room temperature to 800 C, and the friction coefficient is only about 0.3 at 800 C. The wear amount is kept at.600 degrees centigrade at 10-5mm~3/Nm order of magnitude from room temperature to 800 centigrade. The surface generated NiMoO_4 and Ag_2MoO_4 compounds effectively reduce the friction and wear of the coating. In addition, the higher load will promote the process of Ag, Mo and O_2 to produce Ag_2MoO_4 lubricating film, and help compacting the debris to form the protective glaze layer and improve the wear resistance of the coating. (4) the Ag-Mo composite is prepared by the cold isostatic pressure and the high temperature sintering method. The friction and wear properties and the lubrication mechanism of the material were tested and analyzed. It was found that the Ag film spreading on the friction surface was lubricated at low temperature, and a series of low melting point silver molybdate compounds produced at the friction surface at high temperature reduced the friction and wear of the coating. By the study of the mechanism of the solid state reaction of Ag-Mo-O_2, the Ag-Mo-O was established. The _2 three element system generates a solid state reaction model of Ag_2MoO_4. It is found that Ag_2MoO_4 does not evaporate within 1000 C in air and has good wettability to NiCoCrAlY-Cr_2O_3 coating. (5) finite element simulation shows that the higher the elastic modulus of the coating, the greater the stress gradient between the sealing layer and the bonding layer, and the heat of the coating. In the cycle process, the more easy the coating is, the more easy to produce the crack and fall off. Adding Ag in the coating can reduce the modulus of elasticity by 34%, improve the matching of the thermal expansion coefficient of the coating and the matrix, so as to improve the thermal shock resistance of the coating.

【学位授予单位】：中国科学院大学(中国科学院过程工程研究所)
【学位级别】：博士
【学位授予年份】：2017
【分类号】：V263;TG174.4

【参考文献】