Application of the friction surfacing process in a CNC machining center: a viability assessment for producing Al-alloy coatings on low carbon steel

Friction surfacing is a solid-state joining process that can be applied to develop similar or dissimilar combinations/joining partners that exhibit sound mechanical properties while avoiding some of the problems associated with the conventional deposition methods in which fusion is involved. Currently, however, the friction surfacing process is carried out in specialized equipment which do not yet have widespread industrial use. With the objective of exploring new application possibilities, in the present work, the viability of employing the friction surfacing process in a machining center with computerized numerical control was investigated. To this end, the deposition of 6351 Al-alloy coatings on a 1020 carbon steel substrate was pursued. After preliminary tests for determining viable deposition parameters, the influence of process variables (rod diameter, rotation, and forward speed) on coating geometry and mechanical properties was investigated using design of experiments methodology. Adhesion of the coatings was evaluated by applying a simple push-off test. The surface finish of the substrate plate was found to influence heat generation during the deposition process and impacted coating deposition. The results demonstrated that, although parameters must be carefully tuned, the process can be feasibly applied under the experimental conditions investigated, and a maximum push-off force value of 4250 N could be achieved.