Product Code: PIC2008_207

Synthesis and Coating of Aln on Mild Steel by Combined Laser Sol-Gel Technique
Authors:
Marimuthu Sundar, The University of Manchester; Kolkata India
Paul Mativenga, The University of Manchester; Manchester Great Britain
Lin Li, The University of Manchester; Manchester Great Britain
Philip Crouse, The University of Manchester; Manchester Great Britain
Presented at PICALO 2008

In this work a novel method for synthesising AlN coatings is reported. A high-power diode laser at different powers and traverse speeds was applied to a mild steel substrate, coated with a slurry of aluminium hydroxide sol-gel, urea and graphite. The reaction chemical thermodynamics was investigated to estimate the compositions, temperature range, and the required reaction enthalpy for producing AlN. A three-dimensional heat transfer model by CFD technique has been used to predict the processing parameters (speed and power) required to obtain the temperature range during experimentation. Surface morphology and microstructure of the deposited coatings and substrate surface layers were examined using optical microscopy, field emission gun scanning electron microscope which revealed deposition of very thin layer of AlN and the presence of sub-micron crystalline structure of AlN forming a metal matrix composite interlayer with the substrate below the film which suggest a good metallurgical bonding with the substrate. The phases were identified by X-ray diffraction which confirms the synthesis of AlN film for all the samples. Results of micro-hardness measurements revealed a hardness value of the order of 876 HV. The surface roughness of the coating is found to be in the order of 1.8-2.1 µm Ra. The coating exhibits good wear resistance and friction coefficient.