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

Abstract

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.

Investigation of Austenitic Stainless Steel Coatings on Mild Steel Produced by Friction Surfacing Using a Conventional CNC Machining Center

“…In this investigation, it was found that surface roughness did not have a significant influence on coating geometry (thickness and width) but had a strong impact on the adhesion between coating and substrate, evaluated in terms of push-off strength: the lower the substrate roughness, the higher the push-off strength (for Ra = 2.95 µm, the average push-off strength was 5.8 kN whereas for Ra = 0.66 µm the average push-off strength was 10.6kN). In a previous report concerning the deposition of Al-alloy on mild steel the opposite effect was observed 25 . In that case, however, the consumable rod hardness was significantly smaller compared to the substrate.…”

“…The FS procedures were carried out in a ROMI Discover 560 CNC machining center with a power output of 11 kW and maximum rotation of 10000 rpm, as in previous investigations 25,26 . In order to assess the influence of process parameters on coating characteristics, an experimental plan was developed using a simple Design of Experiments (DoE) methodology which consisted of a complete factorial design with three factors and two levels per factor, which yielded a total of 2 3 distinct experimental conditions 27 .…”

“…Recently, attempts have been made to broaden possible applications for the FS process by its employment in nonspecialized equipment [23][24][25] . In an attempt to further explore such possibilities and to advance the current knowledge of corrosion behavior and microstructure formation in FS stainless steel coatings, the present study was conducted.…”