Year: 2015
Type: dissertation
Abstract: Aluminum alloys enable lighter fuel efficient cars making them attractive for automotive applications but they exhibit poor tribological properties. Industrial coatings practices for wear protection are not suitable to protect aluminum as they lack compatible material and feasible manufacturing processes. The purpose of this research is hence twofold: development of a low cost material and a suitable manufacturing process to improve wear resistance of widely used Aluminum alloys The material was iteratively developed from existing Iron manganese (Fe-Mn) alloys which are used extensively in mining applications. Influence of aluminum, chromium and carbon were studied in order to improve both corrosion and wear resistance of the alloy. A laser cladding process was utilized to create desired alloys. Studies were then conducted to understand phase, wear and corrosion property evolution. It was found that at an optimum composition, the material would barely form a galvanic couple with base aluminum alloy. Wear resistance of the alloy was found to be superior to that of conventional stainless steel. The Fe-Mn alloys are one of the hardest steels to work with. They are also susceptible to oxidation and depletion of manganese during processing. Hence existing coating processes are not suitable for deposition. To this end, cold gas dynamic spray (CS) was utilized to deposit Fe-Mn alloys. In order to improve CS deposition efficiency, the process was at first numerically modeled with experimental feedback. In the next step, a novel coaxial laser assisted cold spray process was utilized to enhance deposition. The improved process resulted in Fe-Mn coatings with multifold improvement in deposition rate and bond strength at significantly lower powers densities than competing complex technologies. The influence of laser on bonding mechanism was then studied through a splat level analysis and auger spectroscopy was utilized to understand variations in chemical composition due to the laser irradiation. As a proof of concept, Fe-Mn alloy was coated onto aluminum pucks and evaluated in a scaled disc brake test environment. The material system and deposition process were found suitable and hence present a potential solution to manufacture coated brake rotors.
Author: Vikram Varadaraajan
Language: English
Subfield: Mechanical Engineering
Field: Engineering
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W1561938109