Investigating the friction coefficient in functionally graded rapid prototyping of Al–Al₂O₃ composite prepared by fused deposition modelling

The present research work aims to study the friction coefficient in functionally graded rapid prototyping of Al–Al₂O₃ composite prepared via fused deposition modelling (FDM)-assisted investment casting (IC) process. The optimized settings of the process parameters (namely, filament proportion, volume of FDM pattern, density of FDM pattern, barrel finishing (BF) time, BF media weight and number of IC slurry layers) suggested in the present research work will help fabricate parts possessing higher frictional coefficient.

Initially, melt flow index (MFI) of two different proportions of Nylon6-Al–Al₂O₃ (to be used as an alternative FDM filament material) was tested on the melt flow indexer and matched with MFI of commercially used acrylonitrile–butadiene–styrene filament. After this, the selected proportions of Nylon6-Al–Al₂O₃ were prepared in the form of the FDM filament by using a single screw extruder. Further, this FDM filament has been used for developing sacrificial IC patterns in the existing FDM system which was barely finished to improve their surface finish. Castings developed were tested for their wear resistance properties on a pin-on-disc-type tribo-tester under dry conditions at sliding conditions to check their suitability as a frictional device for industrial applications. In the methodology part, Taguchi L18 orthogonal array was used to study the effect of selected process variables on the coefficient of friction (μ).

It has been found that filament proportion, volume of FDM pattern and density of FDM pattern have significantly affected the μ-values. Further, density of the FDM pattern was found to have 91.62 per cent contribution in obtaining μ-values. Scanning electron micrographs highlighted uniform distribution of Al₂O₃ particles in the Al-matrix at suggested optimized settings.

The present methodology shows the development of a functional graded material that consisted of surface reinforcement with Al₂O₃ particles, which could have applications for manufacturing friction surfaces such as clutch plates, brake drum, etc.

This paper describes the effect of process parameters on wear properties of the Al–Al₂O₃ composite developed as a functionally graded material by the FDM-based pattern in the IC process.