Impact loads developed on a tool cutting edge when milling into a workpiece material are prevailing metrics for explaining coating fatigue failure and the subsequent tool-wear evolution. For predicting related stress and strain fields in the compound coating-substrate, stress, strain, and strain-rate, dependent material properties are required. The attainment of such data is briefly described in the paper. Considering these data, the occurring strains in the cutting edge at various entry impact durations, i.e., strain rates, were calculated and compared with fatigue-critical strains. In this way, the wear phenomena causing the coating failure on the flank and rake during milling were clarified. The attained results were also correlated to corresponding ones in turning, where the dynamic loads of the cutting edge are comparably negligible. The conducted investigations showed that the fatigue-critical strains strongly diminish, when the relevant strain rates increase; thus, leading to a remarkable tool-life reduction. This happens, because the increase of the strain-rate restricts the time for the dislocations movements; thus, regions with stress concentrations occur, deteriorating the material ductility, increasing its brittleness, and diminishing the fatigue critical strains. In cutting operations, where the coating fatigue is the main wear factor, the tool-life can be predicted considering these phenomena. In the paper, relevant experimental analytical procedures are introduced.

The work aimed to investigate the possibility of improving the mechanical properties, and therefore the wear resistance, of coated tools in manufacturing processes with continuous or interrupted cutting loads through appropriate annealing. In this context, PVD CrAlN coatings were deposited on cemented carbide inserts. A part of these coated tools was annealed at a temperature of 400 °C, which was close to the deposition temperature, in an inert gas atmosphere. The annealing duration ranged up to 60 min. Nanoindentations and repeated perpendicular and inclined impact tests were carried out to characterize the strength, fatigue, and adhesion of the tool coatings before and after annealing. According to the results, the mechanical properties of the coating and the fatigue resistance were maximized after a short annealing period of about 15 min, while the adhesion of the coating remained unchanged. These facts led to a large increase in tool life in milling 42CrMo4 QT, when annealed coated tools were applied at 400 °C for 15 min. Furthermore, turning experiments using the mentioned hardened steel as well as GG30 cast iron to produce continuous or interrupted chips, respectively, confirmed the obtained results in milling. Therefore, annealing of coated cutting tools at an optimized duration is recommended as an effective method to extend tool life.

The adhesion, structure architecture, and residual stresses of crystalline diamond coatings (CDCs) on cemented carbide inserts are the factors that significantly affect tool life. The influence of these factors on cutting performance cannot be investigated separately since interactions among them exist. The paper elucidates such dependencies to optimize the CDC architecture and improve cutting performance. In this context, diamond coatings possessing different architectures were deposited on cemented carbide tools. The fatigue endurance and the milling performance of the coated tools were investigated using impact and milling tests, respectively. The residual stresses in the film structures were determined through impact tests and appropriate (Finite Element Analysis) FEA evaluation of the corresponding results. According to the obtained results, the application of a bottom micro-structured CDC prior to the deposition of an upper nanolayered one with inferior thickness improves the coated tools’ cutting performance. An optimum coating architecture is associated with a thickness ratio between the micro-structured bonding to the upper nanolayered CDCs of 2/1. Hereupon, the augmentation of coated tool life via the application of an optimum diamond coating architecture compensates for the high tool cost and improves milling productivity. The latter is further enhanced as the number of tool replacements decreases.

This study investigates the time-dependent corrosion behavior of 6060 aluminum profiles subjected to three industrially relevant surface treatments: clear anodizing, black anodizing, and pre-anodizing followed by polyester powder coating during 30 days of immersion in NaCl solution. Electrochemical Impedance Spectroscopy combined with equivalent electrical circuit modeling was used to monitor corrosion evolution and identify the governing degradation mechanisms. Black-anodized specimens exhibited the highest initial corrosion resistance during the first 4 days of immersion, while clear-anodized specimens provided superior protection between 7 and 15 days due to the formation of a more protective inner oxide layer. Both anodized systems showed evidence of repassivation during prolonged exposure through corrosion product accumulation within the porous oxide structure. The pre-anodized/powder-coated system delayed corrosion initiation beyond 15 days, demonstrating the highest long-term barrier performance. Dynamic perpendicular impact loading after corrosion exposure revealed significant differences in mechanical durability: clear-anodized specimens maintained coating integrity up to 15 days, whereas black-anodized specimens experienced complete coating removal, associated with corrosion-induced microcracks and void formation observed by SEM. Overall, clear anodizing provided the best balance between corrosion resistance and post-corrosion mechanical durability, while the pre-anodized/powder-coated system offered the greatest long-term corrosion protection, demonstrating that the optimum surface treatment depends on the intended service conditions.

Implant-supported overdentures improve denture retention and patient satisfaction, but debonding of attachment housings from the denture base remains a frequent prosthetic complication. This in vitro study evaluated the influence of attachment housing and denture base materials on debonding occurrence and maximum tensile force in resin-cemented attachment housing–denture base complexes subjected to cyclic mechanical loading. Thirty standardized specimens were digitally designed and fabricated from 3 denture base materials—polymethylmethacrylate (PMMA), polyetheretherketone (PEEK), and cobalt-chromium (Co-Cr)—and combined with either titanium or PEEK attachment housings, which were bonded with a dual-polymerized resin cement. Specimens were subjected to 1,100 cycles of alternating tensile and compressive loading, and debonding occurrence and maximum tensile force were recorded. Debonding occurred in 60% of specimens and differed significantly among denture base materials, with no debonding observed in Co-Cr specimens, whereas debonding occurred in 75% of PMMA and PEEK specimens. Co-Cr specimens also demonstrated significantly higher maximum tensile force values than PMMA and PEEK groups, while attachment housing material showed no significant effect. Within the limitations of this in vitro study, the denture base material significantly influenced debonding and tensile force during cyclic loading, whereas the attachment housing material did not demonstrate a significant main effect.

Implant-supported overdentures improve denture retention and patient satisfaction, but debonding of attachment housings from the denture base remains a frequent prosthetic complication. This in vitro study evaluated the influence of attachment-housing and denture-base materials on debonding occurrence and maximum tensile force in resin-cemented attachment housing denture-base complexes subjected to cyclic mechanical loading. Thirty standardized specimens were digitally designed and fabricated from three denture-base materials—polymethylmethacrylate (PMMA) (n = 12), polyetheretherketone (PEEK) (n = 12), and cobalt-chromium (Co-Cr) (n = 6)—and combined with either titanium or PEEK attachment housings, which were bonded with a dual-polymerized resin cement. The specimens were subjected to 1100 cycles of alternating tensile and compressive loading, and debonding occurrence and maximum tensile force were recorded. Debonding occurred in 60% of the specimens and differed significantly among denture base materials. No debond-ing was observed in the Co-Cr specimens, whereas debonding occurred in 75% of the PMMA and PEEK specimens. The Co-Cr specimens also demonstrated significantly higher maximum tensile force values than the PMMA and PEEK groups, while regarding the attachment-housing material, no significant main effect was detected. Within the limitations of this in vitro study, the denture-base material, fabrication, and surface treatment combinations significantly influenced debonding and tensile force during cyclic loading, whereas the attachment-housing material did not demonstrate a significant main effect.