Investigation of Adhesion and Tribological Performance of CrN-, AlTiN-, and CrN/AlTiN-Coated X45CrMoV5-3-1 Tool Steel

Nitriding Effect on the Tribological Performance of CrN-, AlTiN-, and CrN/AlTiN-Coated DIN 1.2367 Hot Work Tool Steel

“…The COF values for HC, HA, and HCA vary between 0.20 and 0.25 in the run-in stage ( Figure 6 a) and can be attributed to the ploughing effect due to asperities and deformation of asperities resulting in polishing and adhesion on the surface at the beginning of the contact [ 35 ]. Previous studies revealed the tendency of the CrN layer to be removed from the surface in the early stages of tribological interaction, in contrast to the relative stability of the AlTiN layer [ 36 , 37 ]. As a result, the tribological pairs change from a ceramic/ceramic to a metal/ceramic contact and can cause a change in the wear mechanism from a two-body to a three-body contact caused by chipping [ 37 ].…”

“…Previous studies revealed the tendency of the CrN layer to be removed from the surface in the early stages of tribological interaction, in contrast to the relative stability of the AlTiN layer [ 36 , 37 ]. As a result, the tribological pairs change from a ceramic/ceramic to a metal/ceramic contact and can cause a change in the wear mechanism from a two-body to a three-body contact caused by chipping [ 37 ]. Although there is no significant change in the COF values for NC and NA surfaces, the COF value of the NCA coating is higher than 0.30 due to the influence of hard particles present in the contact zone ( Figure 6 b).…”

“…The average COF value for the HCA material belonging to the group of coatings with two ceramic layers on the surface increases and rises to 0.26 ( Figure 6 a). The highest COF value for the HCA coating, having the highest hardness among the heat-treated and coated steels, can be attributed to an increase in frictional force resulting from the increase in shear strength, which is the more dominant factor compared to the decrease in contact area [ 37 , 38 , 39 ]. This trend is also observed for nitrided and coated steels.…”

“…The depths of these profiles indicate that all ceramic coatings are removed from the surfaces by the test; however, the resistance of the individual coatings to the wear conditions varies. The AlTiN-coated surface after heat treatment shows a shallower profile compared to the CrN-coated surface due to its higher hardness and better adhesion to the substrate [ 37 ]. On the other hand, the depth and width of the profile become flatter for the CrN/AlTiN coating, which has the highest hardness in this group of coatings ( Figure 8 a).…”

“…The higher modulus of elasticity of the AlTiN coating compared to CrN is therefore reflected in its higher load-carrying capacity, as it has a higher stiffness on the same substrate. Functionally graded design in terms of elastic modulus improves the load-carrying capacity in the CrN/AlTiN coating, since the stresses formed during tribological interaction are transferred to the upper layer, which has the highest elastic modulus in the integral system [ 37 , 44 ]. This improvement in load-carrying capacity is even more clear for the nitrided and integral coated surfaces ( Table 4 ).…”