Abstract
In the present study, the microstructure evolution of WC-10Co-4Cr powder deposited on AISI-SAE 1020 steel substrate by laser cladding was evaluated, considering the effect of average energy per unit area. Single tracks were obtained by employing a Yb: YAG laser system with selected processing parameters. All samples were sectioned in the transverse direction for further characterization of the cladding. Results showed that dilution lay within 15% and 25%, whereas porosity was measured below 12%. According to microstructural analyses, considerable grain growth is developed within the central area of the cladding (namely, the inner region); additionally, the development of a triangular and/or polygonal morphology for WC particles along with a clear reduction in hardness was observed when employing a high average energy. It is worth noting that, in spite of the rapid thermal cycles developed during laser cladding of WC-10Co-4Cr, grain growth is attributed to a coalescence mechanism due to complete merging of WC into larger particles. Finally, the presence of small round or ellipsoidal particles within the inner region of the cladding suggested that non-merged particles occurred due to both an inhomogeneous dispersion and the lack of faced-shaped WC particles.
Highlights
WC-10Co-4Cr composite or alloy is widely used for coating applications in aeronautics, mining, construction, and heavy machinery industries [1,2]
The aim of this work is to evaluate the influence of the average energy per unit area (Ea ) on the geometrical characteristics, porosity, microstructure and hardness evolution in Yb: YAG laser cladding of WC-10Co-4Cr alloy deposited on AISI 1020 steel
Microhardness measurements were recorded along the transversal cross-section of the cladded samples using a HVM ShimadzuTM (Shimadzu, The influence of average energy per unit area (Ea ) on both porosity content and dilution are shown
Summary
WC-10Co-4Cr composite or alloy is widely used for coating applications in aeronautics, mining, construction, and heavy machinery industries [1,2]. Laser cladding (LC) is an industrial manufacturing process that produces dense, crack-free, and low-porosity coatings with excellent bonding properties [5,6]. It has been established that the key processing parameters in LC are the laser power, the scanning speed, and the powder feeding rate, which strongly influence the geometrical characteristics of LC tracks, including aspects such as dilution, width, and wetting angle [7,8,9]. With the purpose of establishing a relationship among three different processing parameters, that is, laser power, scanning speed and laser spot diameter, the concept of Metals 2019, 9, 1245; doi:10.3390/met9121245 www.mdpi.com/journal/metals. Metals 2019, 9, 1245 average energy (Ea ) [10], called average energy per unit area [8,10,11], specific energy [12,13,14,15,16], effective energy [13,17,18] and/or energy density [10,19,20,21,22], is frequently used in the literature; thereby, Ea is basically set by adjusting the corresponding parameters.
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