Catalysis of Rare Earth Element Nd on Boriding of AISI 1045 Steel

Abstract

The present study evaluate the catalysis of Nd₂O₃ on the boriding of AISI 1045 steel using a 5% Nd₂O₃-containing boriding agent in a temperature range of 1213 K to 1350 K for 2 h–5 h. The morphology and types of borides formed on the steel surface were confirmed by optical microstructure, scanning electron microscopy and X-ray diffraction. The results show that the Nd₂O₃ has contrary effects on boriding process, i.e. promotion at high temperatures or hindrance at low temperatures. Nd₂O₃ addition can significantly reduce the activation energy of boride growth at high temperatures, decreased it from 198 kJ/mol to 137 kJ/mol, reduced by 31% in the high temperature range of 1133 K–1213 K as compared with that without Nd₂O₃ addition. The catalysis mechanism of RE element Nd during boriding process was discussed through the analysis of chemical reactions probably occurred in boriding agent, changes in surface morphology and chemical composition.