Influence of boriding on the tribological behavior of AISI D2 tool steel for dry deep drawing of stainless steel and aluminum

Deep drawing of stainless steel and aluminum is a widely adopted method for manufacturing various industrial goods. However, the wear damage produced to die tools is a recurring problem in these processes. While lubricants are often employed to lubricate and reduce die wear, dry deep drawing is the current best alternative for meeting green manufacturing demands. Hence, enhanced solid lubricants or surface treatments for dies are highly required. This study aims to evaluate and compare the tribological behavior of a heat-treated AISI D2 steel and a boriding AISI D2 tool steel against stainless steel (AISI 304) and aluminum alloy (AA 6061 T6) in the absence of lubricant. The boride coating was formed on the AISI D2 steel by the closed-pack boriding technique, resulting in a tooth-saw morphology with an overall thickness of 33.6 mu m. X-ray diffraction analysis confirmed the presence of FeB, Fe2B, and Cr2B3 phases on the surface of the borided AISI D2 tool steel. Notably, the boriding treatment led to a significant increase in the surface hardness of the tool steel, reaching a value of 20.7 GPa. The coefficient of friction (CoF) behavior and wear were evaluated by pin-on-disk tests, simulating conditions similar to those found in cold deep drawing operations. The wear surfaces were analyzed by optical profilometry and scanning electron microscopy (SEM). The results suggest boriding as a suitable treatment to reduce wear damage on the surface of deep drawing dies used for stainless steel and aluminum forming processes in the absence of lubricant. Two-body abrasion and adhesion were identified as the main wear mechanisms in AISI D2 steel against stainless steel and aluminum, with a significant amount of oxidation observed when aluminum was tested. Additionally, a reduction of approximately 20 % in the CoF was observed when employing borided tool steel against stainless steel. However, there was an observed increase of around 75 % in the CoF when the borided tool steel was tested against aluminum.