Fabrication and microstructure of C_aTiO₃ coating by laser cladding

Abstract

In order to explore the way to improve the adhesion of the calcium phosphate bioceramic coating to Ti substrate, the CaTiO₃ coating was fabricated on Ti substrate by laser cladding (LC) using powders of CaCO₃ and CaHPO₄, and then the composition and microstructure of the coatings were investigated. During LC, CaCO₃ can hardly react with Ti, and the coating fabricated using CaCO₃ powder is mainly composed of the process of CaO, the decomposition product of CaCO₃. Moreover, the coating has a loosened structure and part of it has peeled off from the substrate. CaHPO₄ reacts vigorously with Ti, and the coating fabricated using CaHPO₄ mainly consists of CaTiO₃ which is one of the reaction products between Ti and CaHPO₄. Chemical bonding is formed at the interface between coating and substrate, which may enhance the adhesion of the CaTiO₃ coating to Ti substrate. Furthermore, CaTiO₃ dendrite and eutectic of CaTiO₃ and Ca₂P₂O₇ are found on the surface of the coating, implying that a transition can be formed between CaTiO₃ and some calcium phosphate bioceramic. So CaTiO₃ coating fabricated using CaHPO₄ can be a potential candidate to improve the adhesion between calcium phosphate coating and Ti substrate. However, there are also pores and cracks existing in the coating, which may degrade the mechanical properties of the coating.

Keywords

CaTiO₃ coating / CaCO₃ / CaHPO₄ / Ti substrate / laser cladding

References

[1] Gotman I. Characteristics of Metals Used in Implants [J]. J. Endourol., 1997, 11(6): 383-389.

[2] Kim H., Camata R., Lee S., . Crystallographic Texture in Pulsed laser Deposited Hydroxyapatite Bioceramic Coatings [J]. Acta Mater., 2007, 55(1): 131-139.

[3] Ban S., Maruno S. Effect of Temperature on Electrochemical Deposition of Calcium Phosphate Coatings in a Simulated Body fluid [J]. Biomaterials, 1995, 16(13): 977-981.

[4] Singh I., Kaya C., Shaffer M., . Bioactive Ceramic Coatings Containing Carbon Nanotubes on Metallic Substrates by Electrophoretic Deposition [J]. J. Mater. Sci., 2006, 41(24): 8 144-8 151.

[5] Torrisi L., Setola R. Thermally Assisted Hydroxyapatite Obtained by Pulsed-laser Deposition on Titanium Substrates [J]. Thin solid films, 1993, 227(1): 32-36.

[6] Roy M., Vamsi Krishna B., Bandyopadhyay A., . Laser Processing of Bioactive Tricalcium Phosphate Coating on Titanium for Load-bearing Implants [J]. Acta Biomater., 2008, 4(2): 324-333.

[7] Lusquinos F., Pou J., Boutinguiza M., . Main Characteristics of Calcium Phosphate Coatings Obtained by Laser Cladding [J]. Appl. Surf. Sci., 2005, 247(1–4): 486-492.

[8] Heimann R., Wirth R. Formation and Transformation of Amorphous Calcium Phosphates on Titanium Alloy Surfaces During Atmospheric Plasma Spraying and Their Subsequent in Vitro Performance [J]. Biomaterials, 2006, 27(6): 823-831.

[9] Fernández J., Gaona M., Guilemany J. Effect of Heat Treatments on HVOF Hydroxyapatite Coatings [J]. J. Therm. Spray Technol., 2007, 16(2): 220-228.

[10] Patnaik P. Handbook of Inorganic Chemicals[M], 2003 New York McGraw-Hill Professional 100-131.

[11] Yeong K., Wang J., Ng S. Mechanochemical Synthesis of Nanocrystalline Hydroxyapatite from CaO and CaHPO₄ [J]. Biomaterials, 2001, 22(20): 2 705-2 712.

[12] Rakngarm A., Miyashita Y., Mutoh Y. Formation of Hydroxyapatite Layer on Bioactive Ti and Ti6Al4V by Simple Chemical Technique [J]. J. Mater. Sci. Mater Med, 2008, 19(5): 1 953-1 961.

[13] Omori M., Onoki T., Hashida T., . Low Temperature Synthesis of Hydroxyapatite from CaHPO₄· 2H₂O and Ca(OH)₂ Based on Effect of the Spark Plasma System (SPS) [J]. Ceram. Int., 2006, 32(6): 617-621.

[14] Lin L., Lee J., Hsu C., . A Study on the Thermal Properties of Dibasic Calcium Hydrogen Phosphate and Monobasic Calcium Phosphate [J]. Anal. Sci., 1997, 13(Supplement): 413-418.

[15] Hua T., Jing C., Xin L., . Research on Molten Pool Temperature in the Process of Laser Rapid Forming [J]. J. Mater. Process. Technol., 2008, 198(1–3): 454-462.

[16] Kurz W., Fisher D. Fundamentals of Solidification, Aedermannsdorf [M], 1986 Switzerland Trans. Tech. Publications Ltd. 151-186.

[17] Lin X., Yue T., Yang H., . Laser Rapid Forming of SS316L/Rene88DT Graded Material [J]. Mater. Sci. Eng. A, 2005, 391(1–2): 325-336.

[18] Umann M. G., Bezencon C., Canalis P., . Single-crystal Laser Deposition of Superalloys: Processing-microstructure Maps [J]. Acta Mater., 2001, 49(6): 1 051-1 062.

[19] Kou S., Wang Y. Three-dimensional Convection in Laser Melted Pools [J]. Metall. Mater. Trans. A, 1986, 17(12): 2 265-2 270.