How to do friction stir welding of water cooling plate? Is the cost higher than that of buried copper pipes?

yes, it is possible to make the water cooling plate by friction stir welding. The general method is to dig a groove on the base plate, that is, a water tank, and then spread a thin profile plate on the groove surface, and then weld it by friction stir welding to form a waterway. However, it seems that there is a thickness requirement, and it is more difficult to be too thin. Wenxuan thermal friction stir welding water cooling plate will be less expensive than buried pipes.