The aim of the work is to investigate the wear-resistant characteristics of galvanic and vacuum-arc coatings of molybdenum and chromium on X105CrMo17 steel and VT-22 titanium alloy under fretting conditions. The studies were conducted at 20 and 30 MPa, an oscillation frequency of 30 Hz, an amplitude of mutual displacement of the samples of 175 µm, and a number of cycles of 5 x 105. It was found that the vacuum-arc coating of hard chromium under a load of 20 MPa is characterized by wear resistance 2-3 times greater than that of the electrolytic coating: at 30 MPa, signs of seizure appear. High wear resistance of the molybdenum coating applied by the vacuum-arc method was established: at a pressure of 20 and 30 MPa, this coating on the VT-22 alloy is characterized by a decrease in linear wear by 2.6 and 1.2 times, compared to the coating on X105CrMo17 steel. The theoretical aspects of relaxation, hysteresis, and microplastic mechanisms of internal friction under fretting conditions are considered. The use of VT-22 alloy as an inner race with a 70-µm-thick molybdenum coating applied to its surface using a vacuum-arc method is recommended for spherical plain bearings in the aviation industry.
The phase and elemental compositions of the contact layer of AISI 1020 steel (pin) were determined in dry sliding against AISI 1045 steel (disc) under mild (normal) and catastrophic wear conditions. Formation of a tribolayer on the sample contact surface was demonstrated. The layer was consisted of FeO, α-Fe, and γ-Fe phases. A study of the sample morphological features of the sliding surface revealed that this layer was deteriorated by an abrasive mechanism in one sector (sector 1) of the nominal contact area. The other sector (sector 2) was deteriorated with visual signs of melting and adhesive interaction. The main attention was paid to the oxygen concentration as an indicator of FeO formation. A high oxygen concentration (30–40 at%) was observed on the sliding surface in sector 2. Sliding surface area with melt signs was consisted of iron and oxygen. Melt signs were explained by supposition the appearance of strong pulses of electric induction vector in the contact layer (FeO-rich medium) which can transfer the FeO crystal lattice to melt state in thin contact layer during friction. The FeO-melt was not capable for strengthening the tribolayer. The oxygen concentration in the bulk of the tribolayer was less than 5 at%. This indicated weak strengthening of the contact layer due to the formation of crystalline FeO.
The operational viability of offshore renewable energy systems is constrained by the reliability of gear transmission assemblies. This paper provides an exhaustive review of state-of-the-art literature concerning marine gearing, synthesising the multi-physics synergies between mechanical loading and environmental aggression. This review characterises the technical evolution from deterministic industrial standards toward high-fidelity frameworks that account for the coupling of contact fatigue, progressive wear, and electrochemical corrosion. Key focuses include the modelling of emerging subsurface-initiated modes, such as Tooth Interior Fatigue Fracture (TIFF), through depth-dependent material property gradients and multiaxial fatigue criteria. The review evaluates advanced numerical strategies, including the Extended Finite Element Method (XFEM) for autonomous crack path prediction and Rigid-Flexible Multibody Dynamics (MBS) for resolving system-level responses to stochastic Non-Torque Loads (NTLs). Furthermore, experimental validation protocols within the Very High Cycle Fatigue (VHCF) regime and quantitative non-destructive diagnostics, such as Acoustic Emission (AE), are assessed for their role in calibrating Digital Twin and Prognostic Health Management (PHM) frameworks. Finally, considerations are proposed to guide future research, linking microscopic material integrity and macroscopic system reliability for the next generation of offshore renewable energy assets./p>
Abrasive wear remains a critical challenge in tooling and manufacturing processes, as it leads to accelerated material loss, reduced component life, and increased operational costs. This complex phenomenon is governed by dynamic contact conditions, plastic deformation, fracture, and the properties of both the material and interacting abrasive particles. This study uses finite element analysis (FEA) to investigate abrasive wear behavior of JIS SKD11 tool steel coated with Ti- and Cr-based hard coatings, including TiN, TiAlN, CrN, and AlCrN. A single-asperity scratch model was developed to simulate the ploughing wear mechanism, incorporating strain-rate sensitivity via a modified Johnson-Cook model. The simulation results, validated against experimental data, showed good agreement in surface profiles. Wear performance was assessed using degree of wear (ß) and degree of penetration (Dp). TiN exhibited the lowest penetration and highest plastic deformation, indicating strong wear resistance. CrN offered the best substrate protection, while AlCrN showed the highest material loss due to brittle failure. Overall, the findings highlight the critical role of coating selection in improving abrasive durability and demonstrate the potential of advanced FEA-based approaches for optimizing protective coatings in tool steel applications.
The study uses the grey relational analysis (GRA) to maximize the turning conditions of Aluminum Alloy 6061 (AA6061) to obtain an optimal compromise between roughness and hardness of the surface. Even though AA6061 is a high-strength material with a high level of corrosion resistance, the highest machinability is not easily attained. A Taguchi L27 orthogonal array was used to explore the interactive effects of cutting speed, feed rate, and depth of cut. The best parameter combination that was determined through GRA was a cutting speed of 230 m/min, a feed rate of 0.07 mm/rev, and a depth of cut of 0.2 mm, which gave the best Grey Relational Grade of 0.8067 (Experiment 10). The surface finish of 0.53 µm and the hardness of 75.73 HV were excellent. The hypothesis that feed rate has the most significant variable influence on machining outcomes was tested using ANOVA. The outcomes of the ANOVA proved the dominance of feed rate, which has 42.3% contribution to the Grey Relational Grade (p = 0.001), depth of cut (20.6%, p = 0.017), and cutting speed (7.2%, p = 0.21). The remaining error explained 29.9 percent of the overall variation, implying that other variables, including interactions of parameters, wear development of tools or even variability of materials, might affect the performance of multi-objective machining. In contrast to the earlier GRA-based research on AA6061 that dealt with the isolated parameter effects, this study is the first to measure parameter interaction dynamics and provides a statistically rigorous baseline with error contribution analysis (29.9%), as well as an established benchmark of future integration of sustainable cooling strategies.
