航空发动机高温固体润滑-耐磨涂层的制备与研究
文献类型：学位论文
| 作者 | 黄传兵 |
| 学位类别 | 博士 |
| 答辩日期 | 2009-08-25 |
| 授予单位 | 中国科学院过程工程研究所 |
| 授予地点 | 过程工程研究所 |
| 导师 | 张伟刚 |
| 关键词 | 热喷涂 NiCr/Cr3C2-BaF2• CaF2涂层 NiCr/Cr3C2-BN涂层 显微组织 力学性能 摩擦磨损特性 |
| 其他题名 | Study and Preparation of Turbo-Engine’s Coatings with Solid Lubricating and Wear-Resistant Effects Used at Elevated Temperatures |
| 学位专业 | 化学工程 |
| 中文摘要 | 在航空发动机转子轴表面采用热喷涂技术制备高温固体自润滑-耐磨复合涂层，既能降低转子轴的磨损又能减少对磨件的磨损量，满足先进航空发动机刷式封严苛刻工作条件的需要，应用前景广阔。本论文通过研制复合粉体，结合多种热喷涂技术成功制备了NiCr/Cr3C2-BaF2•CaF2和NiCr/Cr3C2-BN复合涂层，考察了涂层材料的结构与性能。论文首次采用加压氢还原、固态合金化及喷雾造粒技术制备了分开包覆型（FKBC）、低压喷雾造粒型（YLBC）和离心喷雾造粒型（LXBC）NiCr/Cr3C2-BaF2•CaF2喷涂粉末，粉末热喷涂工艺性好、沉积效率高。采用等离子喷涂技术制备了YLBC型和具有不同BaF2•CaF2共晶含量的FKBC涂层，采用超音速火焰喷涂和爆炸喷涂技术分别制备了LXBC型和YLBC型涂层。首次制备出适合等离子喷涂的分开包覆型（FKBN）和低压喷雾造粒型（YLBN）NiCr/Cr3C2-BN粉体，采用等离子喷涂制备相应的FKBN和YLBN涂层。研究发现： （1）包覆法制备的粉体能有效抑制碳化物在喷涂过程中的脱碳和氧化，明显提高涂层的均匀性和层状颗粒之间的结合。由于相对高速、低温，超音速火焰喷涂和爆炸喷涂技术制备的LXBC型和YLBC型涂层中物相组成几乎与原始粉末一致。而等离子喷涂FKBC和YLBC型涂层中的主要物相与设计粉末相同，还含有少量的氧化物相（Cr2O3、BaCrO4、NiCr2O4）和其它碳化物相（Cr7C3、Cr23C6），且涂层中存在一定数量的纳米晶粒。 （2）NiCr/Cr3C2-BaF2•CaF2复合涂层的结合方式主要是机械结合，还存在部分的冶金-扩散结合。等离子喷涂YLBC型涂层与FKBC型涂层相比显微硬度相当，但YLBC型涂层颗粒扁平化程度高，物相分布更加均匀，结合强度稍高。与等离子喷涂相比，超音速火焰喷涂和爆炸喷涂涂层的孔隙率分别为约1%和1.5%（不到等离子喷涂涂层的1/4）；涂层的结合强度分别可达约55MPa和70MPa，是等离子喷涂涂层的2倍以上。 （3）等离子喷涂FKBC和YLBC型涂层700~900℃抗热震性能良好，10次热循环无开裂脱落，比较适合的基体是碳钢和Ni基高温合金。700℃涂层的氧化动力学基本遵循抛物线规律，YLBC型涂层的抗氧化性高于FKBC型涂层。发现碳化物的氧化是氧气从表面氧化物膜扩散到氧化物-碳化物界面，通过消耗碳化物相本身而形成的。 （4）等离子喷涂不同共晶含量的FKBC型涂层研究表明，BaF2•CaF2共晶含量为10%的涂层具有最佳的摩擦学特性。随着共晶含量的增加，涂层力学性能下降，摩擦学性能恶化。说明只有当固体润滑剂与基体材料的物理化学性能相匹配，才能形成良好的微观结构并获得较好的综合性能。另外，等离子喷涂YLBC型涂层的摩擦学性能优于同BaF2•CaF2共晶含量的FKBC型涂层。两种涂层在高温下均能有效的降低自身及对磨球Si3N4的磨损。爆炸喷涂和超音速火焰喷涂NiCr/Cr3C2-BaF2•CaF2涂层的摩擦系数比等离子喷涂NiCr/Cr3C2-BaF2•CaF2涂层的摩擦系数更低，耐磨性更好。等离子喷涂、爆炸喷涂和超音速火焰喷涂NiCr/Cr3C2-BaF2•CaF2涂层的摩擦系数最低分别可达0.28，0.29和0.23，显著低于不含共晶的NiCr/Cr3C2涂层最低的摩擦系数0.55。三种NiCr/Cr3C2-BaF2•CaF2涂层的磨损率室温明显高于高温时，但都保持在10-5mm3/Nm数量级。与三种NiCr/Cr3C2-BaF2•CaF2涂层对磨时，相同温度条件下Si3N4的磨损率相当，保持在10-6mm3/Nm数量级。 （5）在室温至400℃时，脆性碎片和Cr3C2-BaF2•CaF2剥离颗粒对热喷涂NiCr/Cr3C2-BaF2•CaF2涂层的磨损进程起主导作用。500℃至800℃时，BaF2•CaF2经历脆性到塑性的转变，塑性变形及连续的BaF2•CaF2转移膜、轻微粘着磨损和粘滞流对热喷涂NiCr/Cr3C2-BaF2•CaF2涂层的磨损进程起主导作用。高温摩擦过程自润滑膜的演变规律为润滑膜的生成-破坏-脱落-再生。BaF2•CaF2共晶是一种性能良好的高温固体润滑剂。 （6）FKBN型NiCr/Cr3C2-BN涂层中氧化物相对YLBN型NiCr/Cr3C2-BN涂层要少。FKBN型和YLBN型涂层具有接近的、较高的结合强度和显微硬度。YLBN涂层物相分布更均匀，孔隙率比FKBN涂层低，两者均具有优良的抗热震性能。YLBN型涂层具有比FKBN型涂层更好的摩擦学特性，其摩擦系数可低至约0.32；以及更低的高温磨损率，仅为FKBN型涂层的50%；对磨球Si3N4的高温磨损也较轻。NiCr/Cr3C2-BN涂层低温下的磨损机理是磨粒磨损和粘着犁削，高温下是粘着和疲劳磨损混合机制，还伴有大量塑性变形和涂层转移到对磨球上。 |
| 英文摘要 | Using thermal spraying technology to obtain composite coatings with solid lubricating and wear-resistant effects used at elevated temperature on turbo-engines would not only reduce both the wear rates of rotor shaft and brushes, but also satisfy the harsh environment need for sealing coatings. In this study, NiCr/Cr3C2-BaF2•CaF2 and NiCr/Cr3C2-BN composite coatings were prepared by using composite powder preparation methods together with thermal spraying technologies, and the microstructure and properties of the coatings were systematically investigated. The obtained main results are summarized as follows: Individual cladding (FKBC), low pressure spray granulation (YLBC) and centrifugal spray granulation (LXBC) NiCr/Cr3C2-BaF2•CaF2 composite powders were developed by using pressurized hydrogen reduction, solid state alloying and spray granulation technologies. The powders have good flowability, apparent density and are suitable for thermal spraying. FKBC, YLBC and LXBC type NiCr/Cr3C2-BaF2•CaF2 composite coatings were fabricated by plasma spray, HVOF and detonation gun spray technologies. FKBN and YLBN type NiCr/Cr3C2-BN composite powders were developed by using pressurized hydrogen reduction, solid state alloying and spray granulation technologies, too. FKBC and YLBC type NiCr/Cr3C2-BaF2•CaF2 composite coatings were then fabricated by plasma spray technology. (1) The analysis of carbon and oxygen in powders and coatings showed that the oxidation, decarburization and ablation of Cr3C2-BaF2•CaF2 during spraying could be reduced by using coated powders.The main phases in HVOF and detonation gun sprayed coatings are almost the same with designed powders due to their relatively high particle velocity and low flame temperature. The main phases in plasma sprayed FKBC and YLBC type coatings are consistent with designed powders, but trace amount of Cr2O3, BaCrO4, NiCr2O4, Cr7C3, Cr23C6 phases were also found in the coatings by TEM. (2) The bonding form of NiCr/Cr3C2-BaF2•CaF2 composite coatings is mainly mechanical bonding with partially metallurgical and diffusion bonding. The microhardness of plasma sprayed YLBC type coating is close to plasma sprayed FKBC type coating. However, the adhesive strength of YLBC type coating is slightly higher than FKBC type coating for the better flat structure and uniform phase distribution. The porosity of HVOF and detonation gun sprayed NiCr/Cr3C2-BaF2•CaF2 coatings are about 1% and 1.5%, respectively, which are less than 25% of that of plasma sprayed NiCr/Cr3C2-BaF2•CaF2 coatings. The adhesive strength of HVOF and detonation gun sprayed NiCr/Cr3C2-BaF2•CaF2 coatings can be up to 55MPa and 70MPa, which are two times more than that of plasma sprayed NiCr/Cr3C2-BaF2•CaF2 coatings. (3) The thermal shock resistance of plasma sprayed FKBC and YLBC type coatings are very well, which can undergo more than ten times thermal cycling between 700℃ and 900℃. Carbon steel and nickel based superalloy are testified to be suitable substrates for NiCr/Cr3C2-BaF2•CaF2 coatings. The oxidation kinetics of plasma sprayed NiCr/Cr3C2-BaF2•CaF2 coatings basically follow the parabolic law, and the oxidation resistance of plasma sprayed YLBC type coating is better than that of plasma sprayed FKBC type coating. Carbide oxidation occurs by diffusion of oxygen through the surface oxide layer down to the oxide-carbide interface. Oxide formation occurs at the oxide-carbide interface by consumption of the carbide phase itself. (4) For plasma sprayed FKBC type NiCr/Cr3C2-BaF2•CaF2 coatings, the coating containing 10wt.% eutectic shows optimum tribological properties at elevated temperatures, depending on the physical and chemical match between the solid lubricant and the matrix materials as well as fine, dense microstructure of this composite coating. With further increasing of BaF2•CaF2 content, the wear rates of NiCr/Cr3C2-BaF2•CaF2 coatings increase rapidly, due to the degradation of mechanical properties. The properties of solid lubrication coatings not only depend on the addition amount of solid lubricant, but also depend on the physical and chemical match (such as coefficient of thermal expansion) between solid lubricants and matrix materials, and microstructure of composite coatings, etc. Only when the physical and chemical properties between solid lubricants and matrix materials matches each other, and the addition of solid lubricant in the coating is appropriate to form well microstructure, comprehensive properties of the coating can be obtained. More over, it also found that plasma sprayed YLBC type coating has better tribological property than FKBC type coating, and the two kinds of NiCr/Cr3C2-BaF2•CaF2 coatings can significantly reduce the wear rate of both themselves and coupled Si3N4 balls at high temperature. The friction coefficients of HVOF and detonation gun sprayed coatings were lower than plasma sprayed coatings, and HVOF and detonation gun sprayed coatings showed better wear-resistance. The friction coefficients of plasma, HVOF and detonation gun sprayed coatings can be as low as 0.28, 0.29 and 0.23, respectively，which are significantly lower than 0.55 of NiCr/Cr3C2 coating. The wear rates of three kinds of thermal sprayed NiCr/Cr3C2-BaF2•CaF2 coatings basically maintain at 10-5mm3/Nm magnitude level, and the wear rates at room temperature are higher than that at elevated temperatures. The wear rates of coupled Si3N4 balls basically maintain at 10-6mm3/Nm magnitude level when sliding against with the three kings of thermal sprayed NiCr/Cr3C2-BaF2•CaF2 coatings. (5) From the investigation of worn surfaces, it was concluded that brittle fracture and delamination were the dominant wear mechanisms of the NiCr/Cr3C2-BaF2•CaF2 coatings at low temperature. A transition stage from brittle to plastic state with decreased shear strength was observed for BaF2•CaF2 eutectic at high temperatures, which resulted in the formation of a continuous lubricating layer in the wear track above 500℃. The evolution rule of self-lubrication layer undergoes the stages of forming, destroying, falling and reforming. BaF2•CaF2 eutectic can be act as a good solid lubricant at elevated temperatures. (6) XRD analysis showed that the oxide in YLBN type coating was lower than that in FKBN type coating. Both two kinds of NiCr/Cr3C2-BN coatings have relatively high adhesive strength and microhardness, and well thermal shock resistance. However, the porosity of YLBN coating is much lower than FKBN coating, and YLBN coating has relatively uniform phase distribution. With comparison to FKBN type NiCr/Cr3C2-BN coating, YLBN type NiCr/Cr3C2-BN coating has lower high temperature friction coefficient, which can be reduced to about 0.32; and has lower wear rates of which is 50% of FKBN coating; the wear rates of coupled Si3N4 balls are also reduced. The wear mechanism of plasma sprayed NiCr/Cr3C2-BN coating was dominated by mixed abrasive and adhesion wear as it slidding against the Si3N4 balls at low temperatures, and it was characterized by mild adhesion and fatigue wear with plastic deformation, as well as coating transfer to coupled Si3N4 balls. |
| 语种 | 中文 |
| 公开日期 | 2013-09-13 |
| 页码 | 213 |
| 源URL | [http://ir.ipe.ac.cn/handle/122111/1259]  |
| 专题 | 过程工程研究所_研究所（批量导入） |
| 推荐引用方式 GB/T 7714 | 黄传兵. 航空发动机高温固体润滑-耐磨涂层的制备与研究[D]. 过程工程研究所. 中国科学院过程工程研究所. 2009. |
入库方式： OAI收割
来源：过程工程研究所
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