Laser Direct Deposition of CoCrAlSiY/YSZ Composites: Densification, Microstructure and Mechanical Properties
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Laser Direct Deposition of CoCrAlSiY/YSZ Composites: Densification, Microstructure and Mechanical Properties Tao Wang1 • Jiaqi Liu1 • Lingchao Qin1 • Jie Tang1 • Jun Wu1
Submitted: 19 September 2018 / in revised form: 26 February 2019 Ó ASM International 2019
Abstract A comprehensive study of densification behavior, microstructural features, microhardness and wear properties of the CoCrAlSiY/YSZ composite coatings fabricated under laser direct deposition (LDD) is presented. The relationship of the laser energy density, microstructures and material properties has been built. Due to the presence of a balling phenomenon at a low laser energy density input, the relative density of the formed materials was low. As the laser energy density was increased to 200 kJ/m, a near-complete densification sample was yielded. At the same time, with the increase of the laser energy density, the microstructure of LDD-prepared CoCrAlSiY/ YSZ composites went from cluster crystals to columnar crystals, to slender and uniformly distributed columnar crystals, and finally to the shape of coarsened columnar crystals. The results of the sliding wear tests indicated that the CoCrAlSiY/YSZ composites prepared by a 200-kJ/m energy density laser had the most uniform microhardness distribution with a mean value of 657 HV0.2, the smallest friction coefficient of 0.4 and the lowest wear rate of
& Jiaqi Liu [email protected] Tao Wang [email protected] Lingchao Qin [email protected] Jie Tang [email protected] Jun Wu [email protected] 1
Department of Mechanical Electronic Engineering, Civil Aviation University of China, Tianjin 300300, People’s Republic of China
2.83 9 10-4 mm3/Nm, which resulted from the finest microstructure of the material prepared by this laser. Keywords CoCrAlSiY/YSZ composites coatings laser direct deposition MCrAlY micro-hardness wear mechanisms
Introduction Additive manufacturing (AM), as one of the leading and advanced manufacturing techniques in the world (Ref 1-3), is widely used in the aerospace, aviation, marine, nuclear, biomedical industries, etc. Laser direct deposition (LDD) is recognized as one of the most versatile AM processes, is able to process a wide range of metals, alloys and composites, and is utilized to coat, manufacture and repair components with complex geometries and strict requirements in the material integrity and the dimensional accuracy (Ref 4-8). Ti6Al4V is a titanium alloy, with a high strength, good plasticity and excellent resistance to corrosion and impact, which is widely used in aerospace, aviation, marine, petrochemic, metallurgy, surgical implants, etc. (Ref 9). However, due to its poor resistance to wear, oxidation and high temperature, its application is limited under the severe conditions of high temperature and severe wear. In order to overcome these disadvantages, some surface coating techniques have been studied and applied to improve the surface characteristics of Ti6Al4V, such as plasma spraying (PS), electroplating and LDD. The functional material
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