‘nanoQuench’ was an Innovate UK project that utilised specialist nanotechnology to reformulate and improve upon existing quenching fluids used in the heat treatment of alloys which are typically applicable to the aerospace industry.
One common cooling technique used in the metal working process of alloys is that of the use of quenching fluids. However during the quenching of aerospace metals it is common for residual stresses to occur in the component, leading to uncertainty surrounding product performance, final machinability and associated service lifetimes. Currently a range of quench media are available, including water, oil and polymer based – each having specific heat transfer characteristics that create specific material properties in the quenched components.
There is a need throughout the aerospace industry to closely control the precise location and rate of heat transfer during the quenching process. This would enable more localised mechanical and material properties to be achieved and lead to significant improvements in alloy performance alongside substantial benefits in productivity and cost efficiency within manufacturing.
The aim of nanoQuench was to focus on the formulation of novel nanofluids at laboratory scale which would provide a greater heat removal performance then current available fluids. The nine month project finished in October 2014 and included CPI alongside The Advanced Forming Research Centre and Primary Dispersions Limited.
The overall outcome of the project concluded that the addition of metal oxide nanoparticles to a quenching fluid can significantly affect the rate of cooling and lead to significant improvements in the microstructure of the resultant quenched part. The project has shown that the rate of cooling can also be adjusted and improved upon through the selection of the metal oxide, its concentration and stabilisation package. The correct selection of metal oxide used can result in later processing steps, such as tempering, being unnecessary.
Working in partnership with CPI and Primary Dispersion Ltd, quenching trials on two different materials (mild steel and IN718 alloy) have been conducted in the Advanced Forming Research Centre using different nano-particles (Al₂O₃ and ZnO₂) mixed with base fluids (De-ionised water, De-ionised water + Polymer, Oil). The objective was to study the effect of the nano-fluids on quenching behaviour in comparison with the performance of the base fluids. Cooling rate and micro-hardness of the samples quenched in various nano-fluids were studied and compared with those obtained from the samples quenched in the base-fluids. The nanoQuench project achieved very promising results and progress is underway for further in-depth research towards commercial applications.Himanshu Lalvani
Manufacturing Engineer, Advanced Forming Research Centre