This Small Business Technology Transfer (STTR) Phase I project aims to develop nanoparticle-based lubricant additives to enhance Minimum Quantity Lubrication (MQL) in high-energy grinding. Nanoparticle-based lubricant additives for specific applications will first be synthesized. Then a special system to deliver tribofilms at the tool-workpiece interfaces for selective lubrication will be developed. This technology is expected to significantly reduce friction and heat generation at the machining interface, resulting in excellent surface finish and reduced thermo-mechanical damage while maintaining surface integrity of machined parts.
The broader/commercial impact of this project will be the potential to provide nanoparticle-based lubricant additives and a delivery system for reduced cost, improved quality, and increased energy saving in a broad range of aggressive machining applications. This technology will also facilitate the replacement of re-circulating lubricant systems, which are sources of variation and significant waste streams.
The Phase I of this project was performed to establish fundamental understanding of behavior of nanoparticle-based lubricants for minimum quantity lubrication (MQL) at machine tool-workpiece interface in surface grinding operations. In current practice, MQL is not widely used in these applications due to oil starvation /burnoff, consequent poor tool life and machined surface integrity. The goal was to improve MQL oil delivery and durability by designing and synthesizing nanoparticles (nanolubricant A, C, and D) integrated with environmentally safe organic agents, and then understanding their behavior at machining interface. The project execution was undertaken by a team of researchers from NanoMech (expertise - nanomanufacturing), academia (expertise – nanotechnology and machining), and their key manufacturing industry collaborators. This collaborative research project was intended to combine the expertise and knowledge in nanolubricant and in machining to work together to design and investigate a solution and study fundamental science for developing a new paradigm in MQL machining based on the advanced nanomanufacturing. Nanolubricants were synthesized using green chemistries of solid nanoparticle cores integrated with fatty acids, emulsifiers, and dispersants. They were successfully dispersed in metalworking fluids and stability of dispersions was monitored over 5 months for keeping the nanoparticles dispersed and forming stable suspensions. Addition of nanoparticles (nanolubricant D) into metalworking fluid showed reduction in coefficient of sliding friction between cubic boron nitride (c-BN) pin and SAE 1045 steel substrates. Nanolubricants showed significant reduction in coefficient of friction (COF) values compared to the base formulations: 1) 34% reduction in COF by nanolubricant compared to that of commercial metalworking fluid; 2) 30% reduction in COF by nanolubricant compared to that of water?based emulsion; 3) 23% reduction in COF by nanolubricant compared to that of vegetable oil. Addition of nanoparticles (nanolubricant D) to base formulations showed significant improvement in material removal and reduction in the density of weartracks on the workpiece surfaces. SEM?EDX analysis of workpiece surfaces showed the formation of low?friction tribofilm with nanolubricant formulations by the shearing of nanoparticles along the sliding direction. Nanolubricants as additives have shown a marked improvement by reducing the grinding thrust and tangential forces using a vitrified c-BN grinding wheel and heat-treated SAE 1045 workpiece. The surface finish is found to be reduced along the grinding direction but increased across the grinding direction which is typical for a sharp high efficiency grinding wheel demonstrating that nanolubricants have facilitated sharper cutting. Nanolubricant additives have been evaluated in this Phase I focused on grinding to demonstrate the efficiency of this technology. A significant reduction in force was seen which leads to an increase tool life and tool performance. This factor is very important as tooling costs are very high and any technology that can improve the efficiency of the machining operation will be well received by metalworking fluid suppliers and end users. This data bodes well for NanoMech’s efforts to utilize nanolubricant for product development and commercialization in collaboration with key industrial partners in Phase II.
