The influence of shoulder-workpiece clearance on channel formation during friction stir channeling at low and high heat inputs

Abstract

Friction stir channeling (FSC) is a newly developed manufacturing process that can replace the traditional fabrication processes of cooling channels for heat exchangers. Regardless of its application, the size and shape of a cooling channel are fundamental to its efficiency. In FSC, clearance between the shoulder of the tool and the workpiece top surface is a prime factor that significantly influences channel size and shape. This study examined the effect of clearance on channel characteristics using two different clearance values, 0.8 mm and 1.2 mm, respectively. The process parameters are chosen in such a way that the effect of clearance can be understood under low and high heat input conditions on several characteristics. These include channel geometry, dimensions, roof thickness, the roughness of the internal surface of the channel walls, and their topography. A rectangular channel geometry with a larger height and width was found to form at 1.2 mm clearance with high heat input parameters. Lower clearance at low heat input resulted in a successful channel, but a higher clearance value produced a defective channel for the same parameters. In conclusion, the results demonstrate how clearance and the amount of heat input are co-dependent to produce a channel with enhanced characteristics that may directly influence the performance of a cooling channel in various heat exchanger applications.