Mechanical Properties and Growth Mechanism of TiB 2 -TiC/Fe Composite Coating Fabricated in Situ by Laser Cladding
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Mechanical Properties and Growth Mechanism of TiB2-TiC/Fe Composite Coating Fabricated in Situ by Laser Cladding Tianwei Yang 1 & Zhaohui Wang 1 & Shihai Tan 1 & Fu Guo 1 Received: 15 May 2020 / Revised: 22 July 2020 / Accepted: 6 August 2020 # Springer Nature B.V. 2020
Abstract
A TiB2-TiC/Fe composite coating was successfully produced on a Q235 substrate by laser cladding through in-situ reactions among 60TiFe, B4C, Cr, Ni, and Si preset powder mixtures. Based on the available literature, scanning electron microscopy images of the mixed precursor powder and coating layer, and corresponding electron dispersive spectroscopy and X-ray diffraction results from the produced coating, the formation mechanism of the TiC-TiB2 composite during laser cladding was determined. The results show that the coating was mainly composed of α-Fe, TiB2, TiC and (Fe, Cr)7C3, where the TiB2 had a dark grey rectangular shape and TiC had a light grey spherical shape. Most of the TiC particles were attached to the TiB2, which means that TiB2 particles were formed before the TiC. The microhardness of the composite coating approached 1260 HV0.2, which shows that the microhardness of the composite coating was more than 7 times that of the Q235 substrate. Furthermore, the wear performance of the coating was obviously improved, to approximately 15 times that of the substrate. Keywords Laser cladding . TiB2-TiC . Formation mechanism . Microhardness
* Zhaohui Wang [email protected] * Fu Guo [email protected] Tianwei Yang [email protected] Shihai Tan [email protected]
1
College of Materials Science and Engineering, Beijing University of Technology, Beijing, Chaoyang District, China
Applied Composite Materials
1 Introduction Low-carbon steel has received considerable interest due to its good mechanical properties and low price. However, during the actual production process, it has been observed that the common failure mechanisms of engineering components include wear, corrosion and fatigue, which causes substantial economic losses. Recently, iron and steel matrix composites reinforced with in situ synthesized ceramic particulates have been the subject of significant investigation [1, 2]. Particulate-reinforced metal matrix composite (MMC) coatings have the advantages of high hardness, high strength and high wear resistance and are promising for various industrial applications [3]. TiC-TiB2 composites have high melting points, high hardness, low densities, excellent thermal stability and good wettability with molten iron [4]. Therefore, they are attractive ceramic reinforcing phases [5]. Directly adding ceramic phases leads to an uneven distribution in the composite coating and poor wetting behaviour between the ceramic phases and the matrix [6, 7]. To avoid the formation of defects from the direct addition of ceramic particles, a new in situ authigenic process has been developed and studied, in which the enhanced phases are formed by chemical reactions during laser cladding and nucleate during the cooling process of the molten pool. Comp
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