Sliding wear of cold sprayed Ti6Al4V coatings: Effect of porosity and normal load

Tribological Performance of Porous Ti–Nb–Ta–Fe–Mn Alloy in Dry Condition

“…Such a difference in wear mechanism may be caused by a dissimilarity in the relative hardness or by the appearance of the wear products at the interface between the target alloy and the counter surface, i.e., the test ball. Since the hardness of the sintered matrix can be expected to be similar, the difference should be attributed to the debris, as observed by Dubrujeaud et al [6] and Munagala et al [5]. For the bulk sample, at the early stage, abrasive wear is likely to set in, but after accumulating plastic deformation, a debris was evidently generated and transferred to the surface of the ball, which is consistent with the observation of Haftlang et al [26].…”

“…This observation indicates that the shift in the COF of the 30% porosity sample is associated with the change of friction mechanism, which is possibly associated with the accumulation of wear debris inside the pores. Such an effect was shown by other authors for a Ti-6Al-4V coating, in which the porosities percentage and pore diameters are approximately 13% and 25 μm, respectively, contributed to the accumulation of debris by the pore-filling mechanism [ 5 ]. The randomness in response of the sample with 30% porosity is attributed to variability of number of pores that are included in the initial contact area.…”

“…This observation is indicative of a distinctive wear system that developed between the two bodies, in which both the effective surface of contact and the debris generated in the process would play a different role. In addition, the amount of surface oxides present in the interior of the sintered structure should be taken into account, as it is known to be potentially detrimental when released as debris [5,6]. Then, the lesser penetration in the more porous sample is indicative of debris removal.…”

“…Ti-based alloys have been widely used in the orthopedic industry and today, as porous materials have gained particular interest due to the possibility of mimicking the elastic modulus (E) of natural bone and thus avoiding failures by stress shielding [1,2]. Nonetheless, the addition of porosity to the metal matrix may also modify other properties related to biocompatibility [3], corrosion [4], and wear resistance [5,6]. Some studies have shown that the corrosion resistance may decrease if porosity is added to Ti-based alloys [7].…”

“…Indeed, intermetallic compounds demonstrate generally superior mechanical properties as compared to solid solutions, increasing stiffness and thus improving wear resistance [12], although some specific types of intermetallic compounds might also be associated with lower machinability [13]. However, there is no agreement on the influence that porosity has on wear and friction performance, in particular the individual aspects of porosity percentage, pore shape, and size, for a given alloy composition [5,6].…”