Abstract
Ni-based alloy powder (NiCrBSi) was applied to prepare coatings on Ti6Al4V by laser cladding to improve the wear resistance of the latter under corrosion. The scanning speed was found to be an essential parameter that could adjust the microstructure of the coatings. Changes in the microstructures of the coatings with the scanning speed were highlighted, and the relationships between the microstructures and microhardness, fracture toughness, corrosion, and corrosion wear resistance of the coatings were established. Results indicated that the matrix changes from Ti2Ni + TiNi to primary γ(Ni) + eutectics (γ(Ni) + Ni3Ti) with increasing scanning speed. Moreover, reinforcement phases changed from TiB2 + TiC (5 mm∙s−1) to TiB2 + TiC + Cr7C3 (11 mm∙s−1) to TiB2 + TiC + Cr7C3 + CrB (17 mm∙s−1). The average microhardness of the coatings first increased and then decreased, and the corresponding fracture toughness showed the opposite trend. The optimum combination of these properties was observed in the coating prepared at 11 mm∙s−1. This coating demonstrated excellent wear resistance in 3.5 wt.% NaCl solution, as well as a high corrosion potential, a low corrosion current density, and a low current density when the electrode initially entered a comparatively stable corrosion state. Moreover, compared with coatings prepared at other scanning speeds, this coating revealed a higher critical potential for oxidation film destruction. The results of this research collectively show that regulating the microstructures of laser-clad coatings by applying different scanning speeds is a feasible strategy to optimize the wear resistance of the coatings under corrosion.
Highlights
The results of this research collectively show that regulating the microstructures of laser-clad coatings by applying different scanning speeds is a feasible strategy to optimize the wear resistance of the coatings under corrosion
The main peaks of Coating 1 could clearly be observed at 2θ = 36.123◦, 2θ = 39.087◦, 2θ = 41.560◦, 2θ = 42.460◦, 2θ = 44.482◦, 2θ = 61.141◦, and 2θ = 77.745◦
Comparison of the d values of these peaks with those in the corresponding JCPDS cards confirmed that TiNi and Ti2 Ni were formed as the matrix phase, while TiC and TiB2 were formed as the reinforcement phase during laser cladding
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. Given the good affinity between these two types of elements, some borides and carbides with high hardness can be in situ synthesized as reinforcements during cladding, greatly improving the resistance of the resulting Ni-based coatings to microcutting [23,24,25]. Other Nibased coatings, such as NiCoCrAlYSi coatings on GH4169 [32] and NiAlVNbB coatings on SUS304 [33], have been produced Despite their many benefits, previous investigations are limited by their focus on the selectivity of Ni-based alloys and other directly added ceramic phases, as well as the effect of the content of a given ceramic on the microstructural and mechanical properties of the resulting coatings [34,35]. As a comprehensive mechanical property, is well known to be closely associated with the resistance to microcutting and brittle debonding The former depends on the hardness of the material, and the latter is related to the material’s cracking susceptibility. The scanning speed resulting in a coating demonstrated optimal corrosion wear resistance was confirmed
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