Effect of Different Concentrations of Nano-Cubic Boron Nitride on the Preparation of TiO₂/Ti/Fe Composite Materials by Thermal Sprayed and Micro-Arc Oxidation

Abstract

In the mechanical, automobile, aerospace, and construction industries, Ti and steel are the mostly commercial materials be used. But the poor hardness, wear, and corrosion resistance limit their applications. In this study, we presented a composite material that consists of thermal-sprayed titanium (Ti) layer on AISI 1020 steel. Then we added different concentrations of c-BN to the electrolyte in the MAO process to enhance the wear resistance and corrosion resistance. The operating parameters of MAO were set to 35 A/dm² current density, 450 V voltage and 10 minutes operating time. The concentration of c-BN added to the electrolytes were 0.1 g L⁻¹, 0.3 g L⁻¹, 0.5 g L⁻¹, 0.7 g L⁻¹, 0.9 g L⁻¹, and denoted as Ti/MAO-BN1, Ti/MAO-BN3, Ti/MAO-BN5, Ti/MAO-BN7, Ti/MAO-BN9, respectively. To determine the properties of the composite coating, measurements of coating thickness, surface roughness, microstructure, hardness, XRD analysis, EDS observations were performed. Then potentiodynamic polarization test and a ball-on-disc wear test were used to determine the corrosion resistance and wear resistance. All the results indicated that all Ti/MAO contained c-BN (Ti/MAO-BN) have higher hardness, lower surface roughness, and thicker coatings thickness than that of Ti/MAO-free (Ti/MAO-F). In the corrosion resistance, Ti/MAO-BN was at least about 64% better than Ti/MAO-F, with Ti/MAO-BN9 being about 5 times better. In the wear resistance, Ti/MAO-BN reduces the wear volume at least about 59% compared to Ti/MAO-F, with Ti/MAO-BN9 reducing the wear volume by about 70%.

During the MAO process, c-BN particles will be encapsulated to form large particles or columnar structures. As more CBN is added to the electrolyte, more large particles and columnar structures will be formed, and the number and size of craters and cracks on the surface of the oxide layer will be gradually filled by large particles and columnar structures and reduced.