The New Jersey Institute of Technology's
Electronic Theses & Dissertations Project

Title:	Multi-component boron coatings on low carbon steel AISI 1018
Author:	Suwattananont, Naruemon
View Online:	njit-etd2010-100 (xxii, 203 pages ~ 14.1 MB pdf)
Department:	Committee for the Interdisciplinary Program in Materials Science and Engineering
Degree:	Doctor of Philosophy
Program:	Materials Science and Engineering
Document Type:	Dissertation
Advisory Committee:	Levy, Roland A. (Committee co-chair) Petrova, Roumiana S. (Committee co-chair) Bozzelli, Joseph W. (Committee member) Mitra, S. (Committee member) Kerwien, Stacey C. (Committee member)
Date:	2010-05
Keywords:	Boronizing Boride Multi-component boronizing Crystal size and microstain Oxidation resistance Corrosion resistance
Availability:	Unrestricted
Abstract:	Boronizing and metalizing are thermo-chemical surface hardening treatments in which boron and metal atoms diffuse into the metal substrate forming metallic boride layers, providing complex properties of B-Me-Fe system. To study multi-component boron coatings on low carbon steel AISI 1018, the simultaneous powder pack method of boronizing and metalizing was selected to perform the coatings. One B-Fe system and eight boron-metal (B-Me-Fe) systems from transition metals group IVB (Ti, Zr, Hf), group VB (Nb, Ta), and group VIB (Cr, Mo, W) were studied. The system specimens were thermo-chemically treated at 950°C for 4 hours in a crucible containing powder mixture of boron source, transition metal powder, and activator. After the heat treatment process, the multi-component boron coatings were characterized by using optical microscope, microhardness tester, TGA, XRD, and Synchrotron microdiffraction. The coating morphology was observed and the coating thickness was measured as well as the microhardness across the depth of coating. The corrosion resistance of the coatings was evaluated by the continuous weighting method. The high temperature oxidation was also detected by isothermal method at a temperature range of 400-800°C for 24 hours. The Rietveld refinement method was used to examine the quantitative phase analysis, crystalline size, microstrain and lattice parameters of the multi-component boron coatings. The results have shown that adding transition metals into the B-Fe system caused the formation of solid solution of transition-metal borides. The distortion of crystal lattice parameters generated microstrain in the boride phase. The Synchrotron microdiffraction confirmed the presence of about 5-10 microns of transition-metal boride phase at the surface. Moreover, the additional transition metal can provide better corrosion and high temperature oxidation resistance to the B-Fe system, preventing the deboronizing and stabilizing the boride phases.