Wear Regime Research Articles

Multibond Model of Single-Asperity Tribochemical Wear at the Nanoscale.

Single-asperity wear experiments and simulations have identified different regimes of wear including Eyring- and Archard-like behaviors. A multibond dynamics model has been developed based on the friction model of Filippov et al. [Phys. Rev. Lett. 92, 135503 (2004)]. This new model captures both qualitatively distinct regimes of single-asperity wear under a unified theoretical framework. In this model, the interfacial bond formation, wearless rupture, and transfer of atoms are governed by three competing thermally activated processes. The Eyring regime holds under the conditions of low load and low adhesive forces; few bonds form between the asperity and the surface, and wear is a rare and rate-dependent event. As the normal stress increases, the Eyring behavior of wear rate breaks down. A nearly rate-independent regime arises under high load or high adhesive forces, in which wear becomes very nearly, but not precisely, proportional to sliding distance. In this restricted regime, the dependence of wear rate per unit contact area is nearly independent of the normal stress at the point of contact. In true contact between rough elastic surfaces, where contact area is expected to grow linearly with normal load, this would lead to behavior very similar to that described by the Archard equation. Detailed comparisons to experimental and molecular dynamics simulation investigations illustrate both Eyring and Archard regimes, and an intermediate crossover regime between the two.

Transition from the boundary lubrication to scuffing – The role of metallic surfaces morphology

Intensive recent research into a better understanding of the scuffing wear of lubricated interfaces has opened new views on the transition from a boundary lubricated regime to catastrophic wear. The present paper focuses on the morphological aspects that can play a determining role in that transition.Manufacturing is frequently based on multi-physical and multi-scale processes, from elastic-plastic deformation (drawing, turning etc.), via abrasive finishing (grinding, polishing etc.) to coatings. These processes introduce numerous morphological modifications to the metallic surfaces of machined items. Therefore, it is important to consider that improper morphology can lead to catastrophic wear. Such a morphology is primarily related to the critical combination of emerging peaks (responsible for unit pressure in the contact area) and valleys (responsible for the oil capacity in the contact area). Hence, the parametric estimation of the surface morphological state is probably crucial in the technology of scuffing prevention. That is the reason why the role of surface morphology in the identification of the transition from boundary lubrication conditions to catastrophic wear is the principal object of this study.The experimental investigations examined the morphological changes of pairs of cooperating surfaces, from "freshly" machined to scuffed states. The frictional process was systematically carried out on a specifically adapted tribometer (a “block-on-ring” system). Explicitly wear-resistant materials (e.g. AISI 4130 steel/EN-GJL-300 cast iron and AISI W1-81/2A steel/EN-GJS-450-10 cast iron) were selected for this investigation, using the same load to cause the transition to scuffing and employing different combinations of more or less efficient lubricants in the boundary regime: either reclaimed naphthenic oil or a chemically-active oil containing a particular additive (an olefin sulphide). The double-blind protocol of these experiments was employed in order to achieve a higher standard of scientific rigour. The strategy was to apply the concept of a morphological precursor to scuffing to the identification of the transition conditions from the boundary lubricating regime to scuffing. The quantification of the morphological transition based on the scientific examination of selected parameters (EN-ISO 25178 and EUR 15178, ISO 16610, ISO 13565-2 and ISO 13565-3, ISO 12085 motifs’ parameters), from normal boundary lubrication to the scuffing wear regime, is presented.

Tribological Behavior of Mg97Zn1Y2 Alloy at Elevated Temperatures of 50-200 °C

The tribological behavior of Mg97Zn1Y2 alloy was investigated using a pin-on-disk wear machine at wear temperatures of 50-200 °C. Morphologies and chemical compositions of worn surfaces were analyzed using scanning electron microscope and energy-dispersive x-ray spectrometer. The microstructural evolution and hardness change in subsurfaces were examined by optical microscopy and hardness tester. The results showed that the wear temperature had significant influence on the coefficient of friction and wear rate. At wear temperatures of 50-200 °C, with increasing applied load, the coefficient of friction went down rapidly then turned to decrease slowly in the mild wear regime, and continuously decreased modestly until the largest applied load in the severe wear regime. Increasing wear temperature from 50 to 200 °C decreased the mild to severe wear transition load linearly from 120 to 60 N. In the mild wear regime, the main wear mechanisms were identified as abrasion + oxidation and delamination + surface oxidation at 50-150 °C, and delamination at 200 °C, while in the severe wear regime, the main wear mechanisms were identified as severe plastic deformation + spallation of oxide layer and surface melting at 50-150 °C, and severe plastic deformation and surface melting at 200 °C. The microstructural transformation from the deformed to the dynamically recrystallized (DRX), and hardness change from the strain hardening to softening were found in the subsurfaces before and after mild to severe transition. The DRX softening mechanism was determined for mild to severe wear transition at 50-200 °C. A wear transition map was constructed for Mg97Zn1Y2 alloy on applied load versus wear temperature.

The Braking Behaviors of Cu-Based Metallic Brake Pad for High-Speed Train Under Different Initial Braking Speed

The purpose of this research was to study the braking behaviors of Cu-based composite pad under real operating conditions of high-speed train. A series of pad-on-disk braking tests was performed with the initial braking speed (IBS) from 80 to 380 km/h. Results showed that the coefficient of friction (COF) of the brake pad demonstrated a three-stage feature with the increase in IBS. It decreased from 0.395 to 0.358 with the increase in IBS from 80 to 200 km/h, then increased to 0.398 when IBS reached 320 km/h; and fell again to 0.379 at 380 km/h. Similarly, the pad also displayed three wear regimes as IBS increased, i.e., (1) mild wear (80–160 km/h), (2) moderate wear (200–250 km/h), and (3) severe wear (300–380 km/h). Surface morphologies and phase analyses indicate that the evolution of the COF mainly depends upon the state of friction film. The formation or completion of friction film regularly contributes to a lower COF and wear rate, while the destruction of friction film results in a higher COF and wear rate. Besides, the “lubricants” induced by high braking temperature are also responsible for the change in the COF. As IBS increased, the key wear mechanisms changed from abrasion, plowing, and oxidation to delamination at 250 km/h.

In situ stylus profilometer for a high frequency reciprocating tribometer

Measuring the friction and wear characteristics of a tribological contact is essential to gaining a detailed understanding of its performance and predicted life. Wear rate and friction coefficient measurements are obtained from instrumented benchtop tribometers designed to replicate specific tribological contacts. Due to the difficulty of measuring wear in situ, measurements are typically made before and after an experiment. The wear rate must be assumed to be linear for it to be used to predict product life, however this is assumption can hide changes occurring during an experiment which indicate wear transitions. This paper details the design and validation of an in situ stylus profilometer for a reciprocating sliding tribometer to provide an insight into the wear transitions occurring during dry sliding of 52100 bearing steel against graphitic flake cast iron. The profilometer’s performance was validated using ground roughness standards and the accuracy found to be approximately 110 nm. Incubation, run-in and steady state wear regimes were identified by the profilometer and corroborated with friction coefficient data, providing an enhanced understanding of the tribological contact behaviour.

Design of composite systems for rotary wear applications

Due to the prevalence of sliding interfaces in mechanical assemblies, fast and reliable wear prediction capabilities are imperative for system design and analysis. This study investigates the rotary wear of multi-material composite systems that have thrust washer geometries. An analytical rotary wear model is developed to predict the rotary wear performance based on Archard's wear law and a Pasternak elastic foundation model. Numerical methods are used to track the evolution of key wear parameters including surface profile, contact pressure distribution, volume loss and composite wear rate during both run-in and steady-state wear regimes. A direct method is also developed to determine the steady-state characteristics from just the initial conditions and configurations of a given composite system. Optimal designs and design guidelines for several wear objectives are identified. Initial optimal material distributions for target steady-state surface profiles are determined. In addition, the steady-state composite wear rate is minimized to reduce material loss for bi-material systems with prescribed volume fractions. It is found that the optimal material configuration for this objective is counterintuitive. Wear tests are conducted to evaluate the proposed models and optimal design solutions. Results obtained from the wear models agree well with the experimental measurements.

Theoretical Approach of Wear for Slide-Friction Pairs

A number of different mechanisms and devices in mechatronic systems may involve sliding-friction surfaces. The issues of service life and its prediction for the details of such surfaces have always been of particular importance. Having studied the wear process prediction theories that have been developed in the course of time, which can be classified by dividing them in definite groups based on similar theoretical approach one can state that each of them has different shortcomings, which might affect the result precision, when essential basic parameters have been disregarded, as well as create a need for useless additional practical experiments, as a result of which theoretical calculation becomes unnecessary. [4] The article determines the most suitable wear calculation model that allows considering the set of parameters necessary for calculating slide-friction pair. Wearing usually proceeds in three stages: the running-in stage, the normal wear stage, and the intensive wear stage. The proposed model is provided for normal wear stage calculations. The proposed model for wear calculation is based on the application of theories from several branches of science to the description of 3D surface micro-topography in accordance with random field theory, assessing the material’s physical and mechanical characteristic quantities, substantiating the regularities in creation of material particles separated during the wear process and taking into consideration definite service conditions of fittings. Since the wear process is variable and many-sided, it is influenced by numerous different parameters, for example, surface geometry (roughness, waviness, form deviation, etc.), physical and mechanical conditions of the upper layer, material components, wear regime, wear temperature, etc. Based on the regularities stated in the article one can propose the following wear calculation sequence [4]:1) Initial data should be stated which will be further necessary in calculations: constructive-kinematic characteristic quantities (rated area Aa of wearing component, load P, gliding movement speed v, movement time t), fatigue characteristic of friction component material (friction coefficient f (f≤0,1) and material fatigue destruction parameters (m, σ-1, N0), mechanical characteristic quantities of material (E, μ);2) Parameters should be stated after attachment: surface roughness parameters (Sa, Sm1, Sm2, Sm2a), initial wear Up and corresponding time Tp, tolerated wear Umax.

Abrasive wear maps for High Velocity Oxy Fuel (HVOF) sprayed WC-12Co and Cr3C2−25NiCr coatings

The friction and abrasive wear behavior of WC-12Co and Cr3C2–25NiCr HVOF sprayed coatings were investigated. The coefficient of friction and abrasive wear rate decreased with increasing sliding velocity, although the magnitude of decrease was different. The operating condition, mechanisms of wear, microstructure and the extent of oxidation influenced friction and wear behavior of the coatings. The wear maps were used to identify transition in abrasive wear rates and severity of oxidative wear. The different wear regimes exhibited by the coatings were attributed to change in relative contribution of mechanical wear and oxidative wear with respect to operating variables. Severity of contact can be used to identify transitions in failure modes from plastic deformation to brittle fracture.

The effect of in-service work hardening and crystallographic orientation on the micro-scratch wear of Hadfield steel

This work presents the micro-scratch wear analysis of a sample of Hadfield steel previously used in a jaw crusher machine. The in-service work hardening material derived from dynamic high loads during the abrasive contact on the steel surface. The scratch resistance of hardened samples was evaluated by micro-scratch tests on a cross-section surface. Scratches were made on a deformed layer and on an undeformed material. In the undeformed region, the two crystallographic planes 001 and 111 were analyzed. The scratch tests were performed under various normal loads (from 20 mN to 250 mN) with a diamond cone stylus of 60° and a 5 μm radius. The electron microscopy techniques (FEG, FIB, and EBSD) were applied to characterize the microstructure, the wear micromechanisms, and the change of the submicrostructure due to scratches and crystallography. Additionally, an optical interferometry analysis was done for the topography characterization of the scratches. The microhardness profile analysis showed a variation of the hardness values from 300 to 700 HV0.3, which resulted from the twinned grains found near the worn surface. Low loads (20 mN and 50 mN) corresponded to mild wear regime, with a wear regime transition at 100 mN. A severe wear regime corresponded to higher loads (150 mN, 200 mN, and 250 mN). A significant variation of the friction coefficient along with the severely hardened layer for low normal loads was not observed. On the other hand, high loads resulted in significant variations of the friction coefficient, without correlation with microhardness profile. Additionally a strong relationship was observed between the scratch wear and the individual grain crystallographic orientation. For scratches in the (001) plane microploughing was established as the predominant wear micromechanism, whereas for (111) plane microcutting was identified as the micromechanism responsible for wear, presenting a higher friction coefficient than for the (001) plane.

Tribological transitions during sliding of zirconia against alumina and ZTA in water

Water-lubricated ceramic bearings are currently being used in engineering applications like water pumps, air compressors and marine systems, due to their higher efficiency, reduced environmental impact and simpler constructive designs. In search of low-cost and high-performance tribosystems, bearings made of dissimilar ceramics are not frequently studied, but have potential to show good tribological compatibility. In this study, tribological behavior of two dissimilar ceramic pairs, ZrO2-Al2O3 and ZrO2-ZTA (10vol% ZrO2), was investigated. Water-lubricated ball-on-disc tests under loads ranging from 6.0 to 24.6 N and sliding speeds from 0.1 to 2.0m/s were performed. Worn surfaces were characterized by optical microscopy, SEM and contact-type profilometry. Thermal (Sc,t) and mechanical (Sc,m) severity of contact models explained the mild to severe wear transition as function of tribosystem's variables such as load, speed, distance, materials’ properties, contact geometry and environment. During mild wear regime, wear rates were smaller than 10⁻⁷ mm³/Nm, friction coefficients remained low (0.1<µ<0.2) and surface roughnesses were reduced during sliding. A mechanical, plasticity-dominated, wear mechanism was observed at ZrO2 balls, while tribochemical wear, mixed with minor ploughing marks and microcracking, prevailed at the wear track of Al2O3 and ZTA discs. For severe wear regime, wear rates of balls and discs were greater than 10−3 and 10−5mm3/Nm, respectively, friction coefficients were high (µ≈0.5) and surface roughnesses significantly increased. Dominant wear mechanisms consisted of plastic deformation, microcracking and material transfer between bodies. The role of water in removing heat from the sliding interface was demonstrated through calculations of contact temperatures and heat partition. The study also showed that it is possible to operate ZrO2 bearings at sliding speeds much higher than previously reported through coupling it with a tribologically compatible counter-body, such as Al2O3 or ZTA, that preferably conducts the heat away from the interface.

Prediction of sliding speed and normal force effects on friction and wear rate evolution in a dry oscillating-fretting PTFE/Ti-6Al-4V contact

Dry fretting wear tests were performed on a semicrystalline polytetrafluoroethylene PTFE cylinder rubbing on a flat Ti-6Al-4V surface at room temperature. Various sliding speeds and normal loads were imposed for test durations from 5×104 to 106 cycles. The purpose of the investigation was to evaluate how sliding speed and normal load influence friction and wear rate evolution for gross slip fretting-reciprocating sliding conditions. Analysis confirmed an initial transient regime related to the progressive formation of a PTFE transfer film on the titanium counterface, followed by a linear steady-state wear regime. Focusing on the steady-state wear regime, a rising staircase evolution versus sliding speed was observed for both friction and Archard's wear rate. This continuous “sigmoid” wear rate evolution was related to friction heating, inducing transition from micro to macro surface-ploughing wear damage. In addition, a discontinuous cracking wear component was observed from a threshold sliding speed (vth=12mm/s), due to friction-induced thermal activation of the crystalline phase transition then the principal transition (associated with the glass transition) of the PTFE polymer. The analysis also showed that an increase in normal load induced a parallel reduction in the coefficient of friction and parallel increase in wear rate. These parallel evolutions suggest no direct interaction between sliding speed and normal force. Hence the normal force effect can be analyzed using a (P/Pref)n weight function, where the n exponent quantifies the relative effect of normal load versus friction and PTFE wear rate. These results, which are discussed regarding former research works of Tanaka, are correlated with PTFE thermo-mechanical response, friction thermal considerations and competition between several wear processes. Finally, global wear rate could be formulated, including sigmoid (ploughing wear), bell shape (cracking wear) and weighted (normal force effect) functions. Good correlation between experiments and predictions confirmed the stability of this formulation.

Tribocorrosion behaviour of a biomedical Ti-25Nb-3Mo-3Zr-2Sn alloy in Ringer's solution

The tribocorrosion behaviour of biomaterial Ti-25Nb-3Mo-3Zr-2Sn alloy in Ringer's solution was evaluated by micro-abrasion experiments, electrochemical tests and scanning electron microscope (SEM) observations. Potentiodynamic polarization results suggested that the effect of particle concentration on the electrochemistry characteristic is greater than the applied load. When the particle concentration and applied load were 0.05g·cm−3 and 0.25N, respectively, the Ecorr reached the maximum as −0.381V. The micro-abrasion-corrosion results showed that the wear rates of the Ti-25Nb-3Mo-3Zr-2Sn alloy increased with increasing particle concentration and decreased as applied load increased. The wear rates acquired under various conditions regarding to the main wear mechanism of two-body grooving wear with less three-body rolling wear; three-body abrasive wear modes are more efficient at material loss than two-body wear. The variation in material loss indicated that the contribution of corrosion is lower than the contribution of micro-abrasion. The wear regime, wastage and micro-abrasion-corrosion synergy maps associated with the particle concentration and applied load were established to evaluate the tribocorrosion behaviour of the Ti-25Nb-3Mo-3Zr-2Sn alloy as a potential surgical implant material.

Comparative Study on the Wear Behaviour of Two High-Temperature-Resistant Polymers

The wear behaviour of two kinds of high performance polymers, i.e. polyetheretherketone (PEEK) and polybenzimidazole (PBI) was investigated at room and elevated temperatures (up to 175 °C). The results showed that PBI possessed better wear resistance than PEEK when the temperature was lower than 70 °C, which can be explained by the excellent thermal mechanical properties of PBI. However, PEEK showed even higher wear resistance when temperature is above 140 °C. It was noted that the formation of an effective TFL plays a key role in determining the wear performance of the polymer/steel system. In particular, the relatively low wear rate for PEEK achieved at elevated temperatures when the “transfer film efficiency factor” was clearly larger than one, although the mechanical properties of PEEK were significantly degraded. This means that under these conditions, the wear process of the polymer would be governed by the damage and regeneration process of the TFL at the interface rather than the bulk properties of the polymer specimen. The selection of high performance polymers for high wear resistance needs to consider not only their thermal mechanical properties, but also the possible wear regime(s) under the sliding conditions in the required applications.

Size Dependence of Nanoscale Wear of Silicon Carbide.

Nanoscale, single-asperity wear of single-crystal silicon carbide (sc-SiC) and nanocrystalline silicon carbide (nc-SiC) is investigated using single-crystal diamond nanoindenter tips and nanocrystalline diamond atomic force microscopy (AFM) tips under dry conditions, and the wear behavior is compared to that of single-crystal silicon with both thin and thick native oxide layers. We discovered a transition in the relative wear resistance of the SiC samples compared to that of Si as a function of contact size. With larger nanoindenter tips (tip radius ≈ 370 nm), the wear resistances of both sc-SiC and nc-SiC are higher than that of Si. This result is expected from the Archard's equation because SiC is harder than Si. However, with the smaller AFM tips (tip radius ≈ 20 nm), the wear resistances of sc-SiC and nc-SiC are lower than that of Si, despite the fact that the contact pressures are comparable to those applied with the nanoindenter tips, and the plastic zones are well-developed in both sets of wear experiments. We attribute the decrease in the relative wear resistance of SiC compared to that of Si to a transition from a wear regime dominated by the materials' resistance to plastic deformation (i.e., hardness) to a regime dominated by the materials' resistance to interfacial shear. This conclusion is supported by our AFM studies of wearless friction, which reveal that the interfacial shear strength of SiC is higher than that of Si. The contributions of surface roughness and surface chemistry to differences in interfacial shear strength are also discussed.

Wear mechanism of flax/basalt fiber-reinforced eco friendly brake friction materials

Fibre-reinforced polymer composites exhibit excellent mechanical and tribological properties. Due to these reasons, they are used in many engineering applications such as transmission and brake systems. In the present study, the wear mechanism of flax and basalt fibre-reinforced phenolic composites was studied using a pin-on-disc wear tester. The sliding conditions such as sliding velocity and normal force varied from 0.1 to 0.5 m/s and 9.81 to 49.04 N, respectively. The wear map of worn-out specimens were analysed using wear mechanism map developed using Fuzzy Clustering Method. Scanning Electron microscopy photographs were examined and wear map was correlated. Different wear mechanisms that dominated a particular wear regime were discussed in this paper.

Impact of surface roughness and contact pressure on wear behaviour of PEEK, POM, and PE-UHMW

Three thermoplastics - PEEK, POM, and PE-UHMW - were investigated in order to highlight the influence of surface roughness, wear regime, and contact pressure on their wear performance and to understand the role each parameter plays in the development of the wear mechanisms. The surface roughness (Ra) was modified in order to reach a high roughness value and a low roughness value. The change in contact pressures was achieved by conducting measurements at the same applied load (30 N) and at the same exerted pressure (62 MPa). The wear regime was varied by increasing the number of testing cycles. The frictional behaviour of PEEK shows a threestage development which is strongly influenced by the increase of roughness and wear regime, whereas in case of PE-UHMW and POM the frictional behaviour does not seem to be affected by these parameters. A strong correlation was observed between material's mechanical properties, wear mechanisms and frictional behaviour.

Wear and Corrosion Behavior of Functionally Graded Nano-SiC/2014Al Composites Produced by Powder Metallurgy

Functionally graded 2014Al/SiC composites (FGMs) with varying volume fractions (1-7%) of nano-SiC particulates (n-SiCp) were fabricated by powder metallurgy. The effect of n-SiCp content on corrosion and wear behaviors was studied. The microstructures of composites were characterized by optical microscopy, scanning electron microscopy and transmission electron microscopy. The corrosion behavior of the composites was evaluated by potentiodynamic polarization scans in 3.5 wt.% NaCl solution. Corrosion results show that corrosion current of composite layer with 3 vol.% n-SiC was much lower than that of 2014Al matrix. Mechanical properties of the composites were assessed by microhardness tests and ball-on-disk wear tests. As the applied load changed from 15 to 30 N, wear rates of the composites increased significantly and the wear mechanism transformed from mild to severe wear regime. It also shows that 3 vol.% n-SiCp/2014Al composite layer observed the lowest wear rate where adhesive and abrasive wear mechanisms played a major role. These results suggest that the n-SiCp are effective candidates for fabricating FGMs for the applications demanding a tough core and a hard, wear or corrosion resisting surface.

Effects of heat treatment and counterface on the wear behaviour of Cr21 cast iron

The unlubricated sliding wear test of high chromium white cast irons (HCCIs) was conducted using a pin-on-disc configuration under different heat treatments and different hardnesses of the counterface. With the increase of counterface hardness (20 HRC–47 HRC–54 HRC), the mass loss of the sample first increases then decreases. When the counterface hardness is 20 HRC, adhesion wear mainly takes place between the high chromium cast iron and the surface of 1045 steel. When the hardness is 47 or 54 HRC, first HCCI’ matrix wear takes place, then carbide bump flakes under alternating stress. The mass loss of the counterface decreases with the increase of hardness for the same sample. The mass loss of quenching, once tempering and twice tempering sample decreases gradually for the same counterface hardness, but fluctuation of the samples’ surface increased. The disc material is always softer than the pin material and results in a severe wear regime operation.

Dry Sliding Wear Behavior and Subsurface Microstructure Evolution of Mg97Zn1Y2 Alloy in a Wide Sliding Speed Range

The wear properties of Mg97Zn1Y2 alloy were investigated using the pin-on-disk wear machine within a load range of 20-380 N and a sliding speed range of 0.2-4.0 m/s. Analysis of worn surfaces using scanning electron microscope and energy-dispersive x-ray spectrometer revealed that wear mechanisms including abrasion + oxidation, delamination accompanied by heavy surface oxidation and delamination operated in mild wear regime, while wear mechanisms such as severe plastic deformation, severe plastic deformation accompanied by spallation of oxidation layer and surface melting prevailed in severe wear regime. The microstructural evolution and hardness change in subsurfaces were examined by optical microscopy and hardness tester. The transformation of surface material from the deformed into dynamic recrystallization (DRX) microstructure was observed before and after mild-to-severe transition. The reason for mild-to-severe wear transition was identified as the transformation of strain hardening to DRX softening in subsurface. Mg97Zn1Y2 alloy has a superior mild-to-severe wear transition resistance to AZ alloys because of its higher recrystallization temperature. A novel model for evaluating the critical surface temperature of mild-to-severe wear transition was established using DRX kinetics.

Suspension High Velocity Oxy-Fuel (SHVOF)-Sprayed Alumina Coatings: Microstructure, Nanoindentation and Wear

Suspension high velocity oxy-fuel spraying can be used to produce thermally sprayed coatings from powdered feedstocks too small to be processed by mechanical feeders, allowing formation of nanostructured coatings with improved density and mechanical properties. Here, alumina coatings were produced from submicron-sized feedstock in aqueous suspension, using two flame combustion parameters yielding contrasting microstructures. Both coatings were tested in dry sliding wear conditions with an alumina counterbody. The coating processed with high combustion power of 101 kW contained 74 wt.% amorphous phase and 26 wt.% crystalline phase (95 wt.% gamma and 3 wt.% alpha alumina), while the 72-kW coating contained lower 58 wt.% amorphous phase and 42 wt.% crystalline phases (73 wt.% was alpha and 26 wt.% gamma). The 101-kW coating had a dry sliding specific wear rate between 4 and 4.5 × 10−5 mm3/Nm, 2 orders of magnitude higher than the 72-kW coating wear rate of 2-4.2 × 10−7 mm3/Nm. A severe wear regime dominated by brittle fracture and grain pullout of the coating was responsible for the wear of the 101-kW coating, explained by mean fracture toughness three times lower than the 72-kW coating, owing to the almost complete absence of alpha alumina.