摘要
本文采用等离子喷涂在TC4钛合金基体上分别制备了常规Metco130涂层及纳米结构Al_2O_3-13wt%TiO_2涂层,并利用CO2激光器对所制备的涂层进行了激光重熔处理,研究了激光重熔对涂层组织结构及性能的影响。
采用X射线衍射分析(XRD)、扫描电镜分析(SEM)、能谱分析(EDAX)、显微硬度试验等方法对激光重熔前后的Al_2O_3-13wt%TiO_2涂层进行了组织结构及性能测试与分析。
试验结果表明,采用等离子喷涂方法制备的涂层与基体形成了较好的机械结合,纳米结构涂层的孔隙率低于Metco130涂层。激光重熔后,获得了表面平整,内部无明显裂纹的激光重熔层。等离子喷涂层的缺陷得以消除,重熔层孔隙率降低,致密度得到了较大提高,且重熔层与基体形成了冶金结合,结合状态良好。
微观组织结构分析表明,等离子喷涂层中相成分主要包括α-Al_2O_3相、γ-Al_2O_3相、TiO_2相及一部分非晶相。激光重熔后,等离子喷涂层中亚稳的γ-Al_2O_3相全部转化成了稳定的α-Al_2O_3相。此外,在重熔过程中, Al_2O_3和TiO_2反应生成了Al2TiO5相,且基体中有部分活性元素Ti渗入到熔池中。粒径分析结果表明,等离子喷涂Al_2O_3-13wt%TiO_2涂层及激光重熔后的Al_2O_3-13wt%TiO_2涂层均处于纳米结构。等离子喷涂纳米结构涂层中主要有两种组织,即熔凝组织和三维网状组织。激光重熔后,纳米结构重熔层组织具有明显的区域特征,在不同区域发现了柱状晶,胞状晶及其混合组织,这是由不同温度条件、不同冷却速度及熔池中不均匀传质等综合因素引起的。
等离子喷涂层的显微硬度约为HV700~1050,是钛合金基体材料显微硬度值的2~3倍。激光重熔后,重熔层的显微硬度可达HV800~1300,其硬度值相对于等离子喷涂层又有了较大提高。
在等离子喷涂及激光重熔过程中,纳米结构涂层表现出了组织结构遗传性。在纳米结构可喷涂喂料中发现了黑白相间的网状组织,等离子喷涂后,网状结构的组织保留到喷涂态的涂层中,最后,在纳米结构重熔层中,仍然可以看到球形放射状组织中包含有网状特征的组织。
In this paper, conventional Metco130 ceramic coating and nanostructured Al_2O_3-13wt%TiO_2 coating have been successfully fabricated by plasma spraying on a titanium alloy (TC4) substrate. A CO2 laser has been used to remelt the plasma sprayed coatings, with the purpose of homogenizing their microstructure, eliminating their porosity and enhancing their bonding strength. The influence of laser remelting on the microstructure and properties of the ceramic coatings was investigated.
The microstructure, phase constitution and microhardness of the as-sprayed and laser remelted coatings were investigated by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive analysis of X-rays (EDAX) techniques and microhardness testing, respectively.
Experimental results show that the as-sprayed coatings maintained good mechanical bonding to the substrate. The porosity of the nanostructured coating is less than that of the conventional Metco130 coating. After laser remelting, the remelted coatings with smooth surface, less crack were obtained. The remelted coatings possessed a more homogeneous microstructure, less porosity, and an excellent metallurgical bonding to the substrate. The defects and porosity of the as-sprayed coatings were eliminated.
The microstructure analysis shows that the plasma sprayed coatings consisted ofα-Al_2O_3,γ-Al_2O_3 and TiO_2 phases. Amorphous phases were also found in the as-sprayed coatings. After laser remelting, the metastableγ-Al_2O_3 phase in the as-sprayed coatings was transferred to stableα-Al_2O_3. In addition, the reaction of Al_2O_3 and TiO_2 led to Al2TiO5. A bit of Ti of the substrate came into the molten pool during laser remelting. The average grain size in the as-sprayed coatings and laser remelted coatings was evaluated using Scherrer Equation. The results show that the plasma sprayed Al_2O_3-13wt%TiO_2 coatings were nanostructured. After laser remelting, the remelted coatings could still keep nanostructured. Two kinds of typical microstructures were found in the as-sprayed nanostructured coatings. One is the full-fused microstructure and the other is the three-dimensional net microstructure. In the laser remelted nanostructured coatings, columnar grain, cellular grain and their mixture microstructure were found in different zone. The different kinds of microstructure were due to different laser heating temperature, different cooling rate and nonuniform mass transfer process.
The microhardness of the coatings before and after laser remelting was determined. It has been found that the microhardness of the as-sprayed coatings was about HV700~1050, which was 2~3 times that of the microhardness of the substrate. The microhardness obtained after laser remelting was up to HV800~1300, which was higher than that of the microhardness of the as-sprayed coatings.
During plasma spraying and laser remelting, the nanostructured coatings possessed microstructure heredity. The three-dimensional net microstructure could be found in the nanostructured feedstock. After plasma spraying, the net microstructure was kept in the as-sprayed coatings. At last, in the laser remelted coatings, the net microstructure feature could be also found in the ball-like micorstructure.
引文
1徐滨士.纳米表面工程.化学工业出版社. 2003: 1~14
2 R. McPherson. A review of Microstructure and Properties of Plasma. Sprayed Ceramic Coatings. Surf. Coat. Technol. 1989, 39/40: 173~181
3张建华,田宗军,赵剑峰,黄因慧,余承业,胡育文,张永康. Al_2O_3纳米复合陶瓷涂层激光熔覆试验研究.激光杂志. 2004, 25(3): 67~69
4张松,张春华,康煜平等.钛合金表面激光熔覆原位生成TiC增强复合涂层.中国有色金属学报. 2001(6): 1026~1030
5熊玉明,朱圣龙,王福会.影响Ti合金热稳定性的因素.腐蚀科学与防护技术. 2001, 13卷增刊: 471~475
6贺志荣.耐蚀Ti合金及其应用研究进展. Ti工业进展. 2000, (4): 38~40
7张晓化,刘道新,唐长斌,高广睿.复合表面改性协同增强Ti合金高温微动疲劳抗力.中国有色金属学报. 2006, (4): 599~605
8 H. Hofmann, G. Frommeyer, C. Derder. Creep Mechanisms in Particle Strengthenedα-Titanium–Ti2Co Alloys. Materials Science and Engineering A. 1998, 245: 127~134
9乌学东,陈海刚,王大璞,杨生荣. WC/Ti合金在水基润滑剂润滑下的摩擦磨损机理研究.摩擦学学报. 1999, (3): 218~223
10张文光,王成焘,刘维民.钛合金表面改性层的摩擦学性能.摩擦学学报. 2003, (2): 91~94
11 D. K. Das, S. P. Trivedi. Microstructure of Diffusion Aluminide Coatings on Ti-base Alloy and Their Cyclic Oxidation Behaviour at 650℃. Materials Science and Engineering A. 2004, 367: 225~233
12 J. C. Williams. Alternate Materials Choices—Some Challenges to the Increased Use of Ti Alloys. Materials Science and Engineering A. 1999, 263: 107~111
13 B. Y. Chou, E. Chang. Plasma-sprayed Hydroxyapatite Coating on Titanium Alloy with ZrO2 Second Phase and ZrO2 Intermediate Layer. Surface and Coatings Technology. 2002, 153: 84~92
14 M. Inagaki, Y. Yokogawa, T. Kameyama. Apatite/titanium Composite Coatings on Titanium or Titanium Alloy by RF Plasma-spraying Process.Thin Solid Films. 2001, 386: 222~226
15陈传忠,李士同,王曙光,陈鹭滨,彭其风,于家洪,雷廷权.等离子喷涂Al_2O_3+ TiO_2复合陶瓷涂层的组织结构.陶瓷学报. 1999, (1): 17~22
16冯拉俊,曹凯博,雷阿利.等离子喷涂Al_2O_3陶瓷涂层的工艺研究.中国表面工程. 2005, (6): 45~48
17顾明兰,田丹碧,朱隽.纳米Al_2O_3的制备和防止团聚技术.吉林师范大学学报(自然科学版). 2004, (1): 14~17
18唐正姣,欧阳贻德,陈中. TiO_2涂层耐蚀性能和抗高温氧化性能.电镀与涂饰. 2003, (1): 45~47
19 Y. Wang, Y. Jin, S. Wen. The Analysis of the Friction and Wear Mechanisms of Plasma-sprayed Coating at 450℃. Wear. 1988, 128: 267~276
20邸英浩,张建新,阎殿然,何继宁,童翔.等离子喷涂纳米Al_2O_3/TiO_2涂层耐磨性的研究.金属热处理. 2005, (3): 4~7
21尹衍升,张景德.氧化铝陶瓷及其复合材料.化学工业出版社. 2001: 27~29
22 A. W. Czanderna, A. F. Clifford, J. Am. Chem. Soc. 1957, 79(5): 5407~5409
23李春福,王斌,张颖,宋开红,罗建民.纳米掺杂Al_2O_3基等离子喷涂层残余应力分析.表面技术. 2004(1): 11~14
24汤文博.等离子喷涂Al_2O_3陶瓷涂层的冲蚀磨损特性.表面技术. 2002, (4): 15~16
25杨元政,刘正义,庄育智.等离子喷涂Al_2O_3+13%TiO_2陶瓷涂层的组织结构及其耐磨性.功能材料. 2000, 31(4): 390~392
26叶宏,张津,孙智富,杨惠,詹捷.镁合金表面等离子喷涂纳米陶瓷涂层研究.武汉理工大学学报. 2004, (4): 9~11
27 Y. Wang, S. Jiang, M. D. Wang, S. H. Wang, T. D. Xiao, P. R. Strutt. Abrasive Wear Characteristics of Plasma Sprayed Nanostructured Alumina-titania Coatings. Wear. 2000, 237: 176~185
28 X. B. Liu, B. Zhang. Effects of Grinding Process on Residual Stresses in Nanostructured Ceramic Coatings. Jounal of Materials Science. 2002, 37: 3229~3239
29 M. Gell, E. H. Jordan, Y. H. Sohn, D. Goberman, L. Shaw, T. D. Xiao. Development and Implementation of Plasma Sprayed Nanostructured Ceramic Coatings. Surface and Coatings Technology. 2001, 146~147: 48~54
30 E. H. Jordan, M. Gell, Y. H. Sohn, D. Goberman, L. Shaw, S. Jiang, M. Wang, T. D. Xiao, Y. Wang, P. Strutt. Fabrication and Evaluation of Plasma Sprayed Nanostructured Alumina–titania Coatings with Superior Properties. Materials Science and Engineering A. 2001, 301: 80~89
31吴子健.热喷涂技术与应用.机械工业出版社. 2005: 1~49
32徐滨士.纳米表面工程.化学工业出版社. 2003: 172~198
33申振华.热喷涂技术的发展及其在航空工业中的应用.航空发动机. 2001, (2): 14~18
34 Y. R. Liu, T. E. Fischer, A. Dent. Comparison of HVOF and Plasma-sprayed Alumina/titania Coatings─Microstructure, Mechanical Properties and Abrasion Behavior. Surface and Coatings Technology. 2003, 167: 68~76
35 K. Vijayakumar, A. K. Sharma, M. M. Mayuram, R. Krishnamurthy. Response of Plasma-sprayed Alumina–titania Ceramic Composite to High-Frequency Impact loading. Materials Letters. 2002, 54: 403~413
36 M. Bounazef, S. Guessasma, G. Montavon, C. Coddet. Effect of APS Process Parameters on Wear Behaviour of Alumina–titania Coatings. Materials Letters. 2004, 58: 2451~2455
37 Y. C. Zhu, K. Yukimur, C. X. Ding, P. Y. Zhang. Tribological Properties of Nanostructured and Conventional WC-Co coatings Deposited by Plasma spraying. Thin Solid Films. 2001, 388: 277~282
38 L. L. Shaw, D. Goberman, R. M. Ren, M. Gell, S. Jiang, Y. Wang, T.D. Xiao, P. R. Strutt. The Dependency of Microstructure and Properties of Nanostructured Coatings on Plasma Spray Conditions. Surface and Coatings Technology. 2000, 130: 1~8
39 J. K. Lee, M. H. Oh, H. K. Lee, D. M. Wee. Plasma-sprayed Al–21Ti–23Cr coating for Oxidation Protection of TiAl Alloys. Surface and Coatings Technology. 2004, 182: 363~369
40 B. H. KEAR and P. R. STRUTT. Chemical Processing and Applications for Nanostructured Materials. Nanostructured Materials. 1995, 6: 227~236
41李志忠.激光表面强化.机械工业出版社. 1992: 10~12
42安耿,梁工英,黄俊达等.激光重熔Cr等离子喷涂层的组织及其导电性的研究.热加工工艺. 2004, 1, 9~11
43张芳.纳米Ni-Co合金的喷射电沉积及其微观组织结构.燕山大学硕士论文. 2002: 25~26
44张晓东.钛合金表面激光熔覆镍包石墨涂层的研究.哈尔滨工业大学硕士学位论文. 2006: 5~6
45江志强,席守谋,李华伦.激光表面重熔等离子喷涂陶瓷涂层的研究与发展.材料工程. 1999, (1): 46~48
46花国然,黄因慧,赵剑峰,王蕾,田宗军,张建华,张永康.激光熔覆纳米Al_2O_3等离子喷涂陶瓷涂层.中国有色金属学报. 2004, (2): 199~203
47刘润,赵剑峰,黄因慧,花国然.纳米复合陶瓷涂层激光熔覆后的组织与耐磨性能.中国表面工程. 2003, (5): 39~42
48张亚平,高家诚,文静,王勇.钛基激光涂覆生物陶瓷涂层的生物相容性.中国生物医学工程学报. 2002, (3): 242~245
49 G. Antou, G. Montavon, F. Hlawka, A. Cornet, C. Coddet, F. Machi. Modification of Ceramic Thermal Spray Deposit Microstructures Implementing In-situ Laser Remelting. Surface and Coatings Technology. 2003, 172: 279~290
50关振中.激光加工工艺手册.机械工业出版社. 1998: 236~239
51 J. A. Picas, A. Forn, G. Matth?us. HVOF Coatings as an Alternative to Hard Chrome for Pistons and Valves. Wear. 2006, 261: 477~484
52何继宁,阎殿然,董艳春,李香芝,刘艳改.等离子喷涂Al_2O_3与Al_2O_3/ TiO_2涂层中的相变及涂层的耐腐蚀行为.金属热处理. 2005, 30(8): 47
53 D. R. Yan, J. N. He, J. J. Wu et al. The Corrosion Behavior of Plasma Spraying Al_2O_3 Ceramic Coating in Dilute HCl Solutions. Surface And Coatings Technology. 1997, 89(1~3): 191~195
54胡汉起.金属凝固原理.机械工业出版社. 2000: 292~293
55 H. P. KIug, L. E. Alexander. X-ray Diffraction Procedures for Polycrystalline and Amorphous Materials. John Wiley&sons, Inc. 1974: 50~51
56孟庆武.钛合金表面激光熔覆复合材料涂层的生成机制与耐磨性能.哈尔滨工业大学博士学位论文. 2006: 5~19
57刘荣祥. TC4钛合金表面激光熔覆NiCrBSi及NiCrBSi/TiN涂层的研究.哈尔滨工业大学博士学位论文. 2005: 9~19
58祝柏林,胡木林,陈俐,谢长生.激光熔覆层开裂问题的研究现状.金属热处理. 2000, (7), 1~4
59 E. M. Levin, H. F. McMurdie. Phase Diagrams for Ceramists. AmericanCeramic Society. 1975, 3: 135
60陈传忠,雷廷权.等离子喷涂激光重熔陶瓷涂层存在问题及改进措施.材料科学与工艺. 2002, (12): 431~435
61刘润,赵剑峰,黄因慧,花国然.激光熔覆纳米Al_2O_3复合陶瓷涂层的组织结构. 2003, 23(5): 258~264
62陈传忠.激光熔覆Al_2O_3+TiO_2复合陶瓷涂层的微观结构.硅酸盐学报. 2000, 28(2): 133~138
63程钢,樊刚.共晶铝硅合金性能的遗传性.特种铸造及有色合金. 2001, (6): 4~5
64魏仑,陈庆华,龙晋明,李建国,蔡英文.激光熔覆原位自生复相陶瓷颗粒增强涂层.激光技术. 2002, 2(4): 246~249
65 J. H. Yao et al. Microstructure and Hardness Analysis of Carbon Nanotube Cladding Layers Treated by Laser Beam. Surface & Coatings Technology. 2006, 201: 2854~2858
66巴伦.纯物质热化学数据手册.科学出版社. 2003: 10~15
67艾桃桃,王芬,朱建锋. Al_2O_3/TiAl复合材料的原位合成及反应机制的研究.金属热处理. 2007, 32(4): 38~41
68 A. Levi. Heridity in Cast Iron. The Iron Age. 1927, (6): 960
69 H. W. Gillet. Heridity in Cast Iron. Metals and Alloys. Trans. AFS. 1934: 15
70 H. W. Lownie. Jr. Use of Pig Iron in Foundries. Trans. AFS. 1956: 104
71 J. Motz. Influence of Trace Elements on the Structures and Properties of Nodular Iron Casting. Giessereiforsching. 1967, (3): 109
72李双寿,朱跃峰,曾大本,吴全虎,李庆荣,顾开广.原料组织遗传性及其在铸造铝合金中的应用.铸造. 1999, (8): 53~56
73周继扬.影响铸铁凝固组织的隐形因素.现代铸铁. 2005, (2): 21~22
74赵宇,周宏,陈莉.添加回炉料后AZ91D镁合金遗传性研究.铸造. 2007, 56(3): 298~299
75 P. Bansal, P. N. Padture, A. Vasiliev. Improved Interfacial Mechanical Properties of Al_2O_3-13wt%TiO_2 Plasma-Sprayed Coatings Derived from Nanocrystalline Powders. Acta Materialia. 2003, 51: 2959~2970