Influence of single point incremental forming on the quality and surface properties of parts manufactured with aluminized steel sheets pre-coated with PTFE

Abstract

Hot dip coated steel/aluminium sheet is commonly used in heat exchangers or in industrial baking trays due to its great heat return capacity and anticorrosive protection and polytetrafluoroethylene (PTFE) is known for its low surface energy which gives it a low coefficient of friction and great hydrophobicity. Usually, aluminized steel sheets are formed to later apply the coating, which requires specialized processes that could be streamlined with the supply of pre-coated sheet, making the final product cheaper. In the present work PTFE coating has been applied on DX51D aluminized steel sheets which have then been processed by single point incremental forming using a protective sacrificial plate (dummy) to prevent deterioration of the coating. The influence of the technological input variables (rotational speed, feed rate, Z-stepover, wall angle and dummy) on the final quality of the coating (coating thickness, hardness, roughness, durability and sliding angle) has been studied, also analysing the deformation-flatness relationship and the effect of the inherent temperature of the process. The specimens showed a noticeable improvement in their hydrophobicity caused by surface changes as a consequence of the applied deformation and the consequent elastic recovery of the composite, maintaining good durability against abrasion resistance. Softer deformation values (wall angle, A) combined with a slower movement of the forming tool (feed rate, F) allowed to obtain a product with better geometric quality even improving its hydrophobicity maintaining good coating quality.