Boron induced surface modification of transition metals

Boronizing is a thermo-chemical surface treatment of metals in which boron atoms diffuse into the metal substrate and form hard metallic borides. As a result of boronizing, several properties such as hardness, wear resistance, corrosion resistance, and high temperature oxidation resistance improve which make the metal substrate more suitable for industrial applications. These boronized parts are used in many industrial applications like ingot moulds, crucibles, biomedical implants, die-casting moulds, magnetic head applications, drawing dies etc. The objective of this work was to investigate the influence of boronizing on the properties of transition metals. Three transition metals, tantalum, niobium and tungsten were considered in this research. After boronizing, tantalum, niobium and tungsten exhibited a coating thickness of 3 μm, 10 μm and 10 μm respectively. The obtained coating exhibited a columnar structure showing a good adhesion with the substrate. The presence of boron was confirmed by the X-Ray analysis. The coating has a microhardness of 3200 HV, 3300 HV and 3200 HV for tantalum, niobium and tungsten respectively. Potentiodynamic corrosion resistance testing was performed in 4% NaCl for the three metals. The boronized transition metals exhibited better resistance to polarization than the unboronized transition metals indicating better corrosion resistance for the boronized metals than the unboronized metals