Micro-abrasive Wear Tests Research Articles

Influence of DLC Film Deposition on the Corrosion and Micro-abrasive Wear Tests of the 2524-T3 Al Alloy

The 2524-T3 aluminium (Al) alloy produced by ALCOA may be used as skin material by the aircraft industry. Some studies are available in the literature about fatigue and fatigue - corrosion behaviour of 2524-T3 Al alloy. However, the corrosion mechanisms are not yet fully understood since the material has a very complex microstructure due to impurities and the addition of alloying elements which lead to an increase in the localized corrosion process. It is known that the corrosion process in Al alloys, most of the time, is due to the galvanic coupling of the intermetallic particles (IMs) and the Al matrix. Thus, the use of protective coatings appears as a possible alternative against the advancement of the corrosion process of the 2524-T3 alloy. In this way, a set of DLC films was obtained by using physical vapor deposition (PVD) method and characterized by various techniques including scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), Atomic force microscopy (AFM) and Raman spectroscopy. The deposited films on the surface of the 2524-T3 Al alloy were characterized electrochemically by using potentiodynamic polarization curves (PPc), electrochemical impedance spectroscopy (EIS) and mechanically by using micro-abrasive wear tests (MAWTs). The results show an advantage in using the PVD method to produce thin films on the 2525-T3 Al alloy surfaces, as the wear resistance of the Al alloy coated by DLC film is higher than for the bare material and the corrosion resistance of the material is not compromised. DOI: http://dx.doi.org/10.17807/orbital.v11i2.1321

Effect of microstructure on wear performance of NiCrSiBC coatings

An investigation was conducted to determine the extent to which the microstructure of NiCrSiBC alloy coatings influences micro-abrasive wear resistance. The wear performance of the complex microstructure in coatings is strongly dependent on nature of the strengthening particles. Processing conditions can be altered to manipulate these particles and therefore to design coatings to address specific service demands. The purpose of this investigation was to evaluate the relationship between microstructure and micro-abrasive wear performance of NiCrSiBC coatings. Differences in the microstructure of coatings were imposed by processing with Plasma Transferred Arc (PTA) and High-Power Diode Laser (HPDL). The microstructures of NiCrSiBC coatings were evaluated using EDX, XRD, SEM techniques and hardness measurements. Wear performance was assessed by micro-abrasive wear tests in which normal load, sliding distance and ball sliding speed were varied. A suspension of alumina in water was used as the abradant. The features of the strengthening particles were observed to depend on the imposed solidification/cooling rate. A faster cooling rate, produced by HPDL processing, displayed block shape chromium borides (CrB) in finer structure coatings. This contrasted with PTA-processed coatings which exhibited floret-shape chromium borides (Cr5B3) in a coarser microstructure. Higher hardness coatings with finer microstructure exhibited lower abrasive wear resistance than the coatings with coarser microstructure.

Effect of ball rotation speed on wear coefficient and particle behavior in micro-abrasive wear tests

In this work, the effect of ball rotation speed on the micro-abrasive wear test was analyzed, both in terms of the wear coefficient and of the behavior of the abrasive particles. Tests were conducted in an equipment with fixed-ball configuration, on specimens made of AISI 1020 low-carbon steel. The ball was made of quenched and tempered AISI 52100 steel and the rotation speeds of 40, 80 and 150 rpm were selected. Two values of normal load were used, 0.2 and 0.4 N. The abrasive particles were made of silicon carbide (SiC), with average particle size of 6.6 µm. The experiments were conducted in sets with different concentrations. Additional tests were conducted with a lower value (2.1 µm) of average particle size. The wear coefficients were plotted as a function of the rotation speed. Results indicate a trend for the decrease in wear coefficient and increase in the number of abrasive particles entrapped on the specimen surface with the increase in rotation speed.

Effect of ionic plasma nitriding process on the corrosion and micro-abrasive wear behavior of AISI 316L austenitic and AISI 470 super-ferritic stainless steels

The aim of this work was to study the influence of thermochemical treatment of ionic plasma nitriding on the resistance to micro-abrasive wear and to the corrosion process of AISI 316L and AISI 470 stainless steels. The thermochemical treatment was performed at different times and temperatures with a gas mixture of 25% H2 and 75% N2. The treated materials were characterized by using optical microscopy (OM), scanning electron microscopy (SEM), X-ray diffraction (XRD), microhardness tests, micro-abrasive wear tests (MAWTs) and corrosion tests. The results show an increase in the thickness of the layer formed by increasing treatment time and in the wear resistance of the materials studied. Temperatures exceeding 450°C favor the formation chromium nitrides, which, for being very hard broke making the formed layer brittle decreasing the wear resistance of the material. In addition, the formation of these phases substantially decrease the corrosion resistance of stainless steels.

Corrosion and Micro-abrasive Wear Behaviour of 2524-T3 Aluminium Alloy with PAni-NPs/PSS LbL Coating

In this paper, we present an alternative method to obtain thin films for coating protection on the surface of the AA2524-T3 Al-alloy by using the Layer-by-Layer (LbL) technique. The LbL films were fabricated by alternated immersion of the Al-alloy into a poly(styrene sulfonate) (PSS) and polyaniline nanoparticles (PAni-NPs) solutions, obtaining a PAni-NPs/PSS bilayer architecture. The LbL films were characterized by ultraviolet-visible spectroscopy (UV-Vis), Fourier-transform infrared spectroscopy (FTIR), atomic force microscopy (AFM), electrochemical and micro-abrasive wear tests. The results show that the number of bilayers promotes shifts to less negative potentials, indicating an optimized system, in which the best performance was observed for a 15-bilayer PAni/PSS LbL film. The pitting potential (Epit) values shifted 130 mV (from -610 mV to -480 mV) in comparing a bare Al-alloy. The predominantly wear mechanism for AA2524-T3 with PAni-NPs/PSS bilayers was scratching whereas for the bare material there was an equivalence between scratching and rolling mechanisms. The results proved that the incorporation of PAni-NPS by the LbL method may be propitious as protective coating against corrosion in AA2524-T3 alloy.

Wear resistance of the pressure armor submitted to deep cryogenic treatment and plasma nitriding

Risers are multilayer structures used in oil production and transportation. The pressure armor is the layer responsible for supporting the internal radial pressure and is produced from a helical interlocked steel wire. The interlocking mechanism, which gives flexibility to the riser, is responsible for the wear on the pressure armor, resulting in a micro-abrasive wear. The present work aims to study the effect of deep cryogenic treatment and plasma nitriding on the micro-abrasive wear in the pressure armor. Samples tested were taken from the contact region of the pressure armor. The micro-abrasive wear test was performed on a free ball machine. The tests were conducted on the samples as received, with deep cryogenic treatment and with plasma nitriding (at 515 °C for 8, 24 and 48 h). It was observed that the material with deep cryogenic treatment had a Vickers microhardness profile and wear coefficient similar to the sample as received. The nitrided samples showed a higher (21.8%, 23.2% and 29%) microhardness value at the surface region than the sample as received and an improvement in wear coefficient in the transient (29.85%, 28.53% and 29.81%) and permanent (19.18%, 25.19% and 28.09%) regions.

The influence of diamond-like carbon and anodised aluminium oxide coatings on the surface properties of the SAE 305 aluminium alloy

This paper presents an analysis of two surface treatments applied on the SAE 305 aluminium alloy: a diamond-like carbon coating and an anodisation process. The objective is to verify a potential wear resistance increase on the clamp-cable interface of an overhead transmission system. The evaluation of the coatings was carried out using micro-indentation technique, micro-abrasive wear tests and surface analysis. The parameters under study are hardness, roughness, wear volume and wear regime. The diamond-like carbon coating showed a significant improvement in wear resistance, whereas the anodisation process led to the opposite effect. The porosity of the anodised coating was identified as a cause for the wear resistance decrease while the enhancement provided by the diamond-like carbon coating is attributed to its high hardness, low roughness and to the occurring three-body wear regime.

Characterization of Niobium Carbide Layers Produced in Ductile Cast Iron Using Thermo-Reactive Treatments

Abstract Ductile cast irons are materials with good ductility and toughness, but they are susceptible to high wear rates since they have low hardness. One way to increase their wear resistance is through thermo-reactive diffusion treatments (TRD), in which carbide layers are produced on the surface of the material. In this study, two ductile cast irons (with and without the addition of copper) were treated in a salt bath composed of borax, ferroniobium (16 wt.%) and aluminum (3 wt.%) at 1000°C for 4 h. The XRD and micro-hardness analysis indicated that NbC layers were produced with hardness values higher than 2000 HV. Two methods were used to examine the adherence of the layer to the substrate. In the first method, indentations were performed using Rockwell C scale (VDI 3198). The second method used Vickers micro-hardness indentations (loads 100, 200, and 300 gf) at the interface layer/substrate. In both tests, the layers showed good adhesion to substrates. The 3198 VDI test also showed that the NbC layer produced good toughness. The results of micro-adhesive and micro-abrasive wear tests showed that the layer was very effective in increasing wear resistance.

Strain Hardening: Can it Affect Abrasion Resistance?

It has been largely reported in the literature that previous strain hardening has none or negligible effect on abrasive wear resistance. Those results are mainly obtained using sand rubber wheel tests and pin-on-disk tests, and have been attributed to the large strain hardening promoted by the abrasion phenomena themselves. The stresses involved in those tests are very high and the stress distributions spread toward subsurface regions at large depths. This work investigates the effects of strain hardening on low-severity (low stress at low depth) abrasive wear resistance. Microabrasion tests, normally regarded as lower stress tests, were used in order to impose low severity. Two types of stainless steels were tested: an austenitic AISI 304 steel and a ferritic AISI 430 steel. Strain hardening was obtained via thickness reduction (20%) of stainless steel sheets in a laboratory cold rolling mill. The microabrasion wear tests were carried out in a fixed-ball microabrasion tester with a three-axis load cell to continuously and simultaneously monitor the forces involved in the tests. Contrary to many findings so far in the literature, previous strain hardening increased abrasion wear resistance (55 and 63%, respectively) for both materials. Hertz calculations, simulations using Finite Element Program with explicit solution, conventional mechanical tests, microhardness profiles, microstructural analysis, and X-ray diffraction analysis were used to explain this paradigm shift for the case of microabrasion tests.

Abrasive wear of multilayered/gradient CrAlSiN PVD coatings: Effect of interface roughness and of superficial flaws

PVD coatings have been used to improve the wear resistance of various tribological systems. In general, analytical models that describe the abrasive wear behaviour of ceramic materials do not take into account the presence of superficial flaws in ceramic coatings. Flaws are pores or protuberances present in the coating surface formed during the coating process. In this work, the percentage of superficial flaws was measured using optical microscopy and was correlated to the abrasive wear resistance of the investigated coatings. Two different coating designs were analyzed, multilayer and gradient. In both coating architectures, the chemical composition at the coating-substrate interface was kept constant at 75% of CrN and 25% AlSiN, and the CrN/AlSi ratio was varied throughout the coating thickness. The mechanical properties of the coatings were evaluated using Knoop microhardness tests and progressive load scratch tests. The presence of flaws in the coatings was connected to the substrate roughness values. Free-ball microabrasive wear tests were carried out using SiC abrasive slurry with a concentration of 20 wt%. Wear rates of the coatings increased linearly with e.Lc−3/4.H−1/2, where e was the superficial flaws fraction, Lc the critical load measured in the scratch tests and H the microhardness. The coating wear rates were intensified up to 72% by increasing the interface roughness. The wear rate of 2.6µm thickness coatings was about 120% higher than the 3.1µm thickness coatings. This work showed that the percentage of superficial flaws was a key parameter that affected the wear rate and critical load of the coating. This result was related to the fact that superficial flaws acted as stress concentration sites that raised the local stress leading to premature failure of the coating during the wear process. The combination of these techniques afforded a powerful tool with which to develop an efficient and reliable methodology for characterizing tribological coatings.

Improving the Wear Resistance of Moulds for the Injection of Glass Fibre–Reinforced Plastics Using PVD Coatings: A Comparative Study

It is well known that injection of glass fibre–reinforced plastics (GFRP) causes abrasive wear in moulds’ cavities and runners. Physical vapour deposition (PVD) coatings are intensively used to improve the wear resistance of different tools, also being one of the most promising ways to increase the moulds’ lifespan, mainly when used with plastics strongly reinforced with glass fibres. This work compares four different thin, hard coatings obtained using the PVD magnetron sputtering process: TiAlN, TiAlSiN, CrN/TiAlCrSiN and CrN/CrCN/DLC. The first two are monolayer coatings while the last ones are nanostructured and consist of multilayer systems. In order to carry out the corresponding tribological characterization, two different approaches were selected: A laboratorial method, using micro-abrasion wear tests based on a ball-cratering configuration, and an industrial mode, analysing the wear resistance of the coated samples when inserted in a plastic injection mould. As expected, the wear phenomena are not equivalent and the results between micro-abrasion and industrial tests are not similar due to the different means used to promote the abrasion. The best wear resistance performance in the laboratorial wear tests was attained by the TiAlN monolayer coating while the best performance in the industrial wear tests was obtained by the CrN/TiAlCrSiN nanostructured multilayer coating.

Microstructure and Mechanical Properties of Borided Inconel 625 Superalloy

The Ni- based superalloy Inconel 625 is extensively used owing to its high strength, excellent fabricability, good weldability and outstanding resistance to high temperature corrosion against aggressive environments. However, despite its unique properties and extensive use, its wear resistance is in some cases unsatisfactory. In this study, Inconel 625 was subjected to boriding treatments at different temperature and different durations. Microstructural characterization was made by conventional methods (scanning electron microscopy, optic microscopy, X-ray diffraction analysis) and mechanical characterization was made by microhardness and micro-abrasion wear test. Micro-abrasion wear tests were conducted against a AISI 52100 steel under 5, 7.5 and 10 N load in a 25 wt.% SiC slurry at room temperature. Microstructural results revealed that multi-phase boride layer (nickel boride, chrome boride and iron boride) and silicide layer were formed. The hardness and thickness of the boride layers were found to be 1175--2432 HV0.1 and, 6.61 -- 92.03 I¼m, respectively. Depending on the boriding temperature and time. In spite of silicide layer formation the wear resistance of borided Inconel 625 alloy increased up to 8 times thanks to the increase in the surface hardness which was caused by boriding process. The boriding treatment caused a transition in the wear mechanism. While grooving was observed in the untreated Inconel 625 samples, mixed (grooving and rolling) and rolling type wear was predominant in the borided samples.

Wear Behavior of a Borided Nickel-Based Self-Fluxing Thermal Spray Coating

Increasing the hardness of materials used in machines can lead to a longer useful life while decreasing maintenance downtime. However, high hardness usually results in an increase in brittleness of the material, which can be avoided by surface treatments, such as thermal spray coatings that are largely used to produce coatings with high resistance to wear and corrosion. This method has advantages, such as easy application, relatively inexpensive in comparison with other methods, and does not increase the brittleness of the base material. However, in some applications, the wear resistance may not be sufficient. To further improve the wear resistance of these coatings, a thermochemical boriding treatment can be subsequently applied to produce a duplex coating. In this work, an SAE 1020 steel was used as the substrate for the application of a thermal sprayed surface coating. The alloy applied is nickel based and self-fluxing with composition NiCrBSiC. The boriding treatment was subsequently performed at 850°C for 2 h. Optical microscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction, and Vickers micro-hardness and micro-abrasive wear tests were used to characterize the samples. The flame spray produced coatings of approximately 900 HV, which was increased to 1600 HV after the boriding treatment.

Characterization of Layers Produced by Boriding and Boriding-PVD on AISI D2 Tool Steel

Boride layers with high hardness and wear resistance were produced on AISI D2 tool steel by thermo-reactive treatment using borax with the addition of 10 wt. % aluminum. Subsequently, PVD treatments were performed on the borided layer. The samples were characterized using optical microscopy, scanning electron microscopy, X-ray diffraction, micro-hardness testing, and free-ball micro-abrasive wear test. The boriding treatment time was 4 h, followed by cooling in oil or air. The average thickness of the borided layers was 120 μm with a hardness ranging from 1400 to 1700 HV. The micro-abrasive wear tests were performed using an abrasive solution of silicon carbide. All layers produced exhibited a wear resistance much higher than that of the substrate. Samples with duplex PVD plus boriding treatments yielded the best wear performance, followed by the borided steel samples, and finally, the untreated quenched and tempered samples.

Effect of a Deep Cryogenic Treatment on Wear and Microstructure of a 6101 Aluminum Alloy

The aim of this work is to evaluate the effect of a deep cryogenic treatment (DCT) on the wear behavior and on the microstructure of an aluminum alloy. In order to compare the level of improvement on the wear resistance provided by the DCT with a more traditional technique, a test matrix which included DCT, CrN coated specimens, and combinations of both modification methods was conducted. The wear behavior was investigated using microabrasive wear tests. The cryogenic treated specimens proved to have similar low wear rates as the specimens coated with CrN. The most distinct improvement was reached with a combination of both techniques. In the case of the DCT, the performed microstructural analysis identified the generation of additional GP-zones as the reason for the improved wear resistance.

Analysis of the micro-abrasive wear behavior of an iron aluminide alloy under ambient and high-temperature conditions

This study examines the micro-abrasive wear behavior of an iron aluminide alloy to determine correlations between the abrasive wear modes, volume of wear (V), and coefficient of friction (µ). Experiments were conducted with a specimen of Fe–30Al–6Cr (at.%) iron aluminide alloy, a sphere of AISI 52100 bearing steel and abrasive slurries prepared with black silicon carbide (SiC) particles and glycerin. Different levels of sliding distance (S), normal force (N), abrasive slurry concentration (C), and temperature of test (Te) were used for the micro-abrasive wear tests by rotative ball; during the experiments, the abrasive slurry was continuously agitated and fed between the sphere and the specimen, and, in parallel, the normal (N) and the tangential (T) forces were simultaneously monitored. Subsequently, the volume of the craters and the coefficient of friction acting in the tribological system “sphere–abrasive particles–specimen” were calculated. The results showed that i) the abrasive wear mode reported for all wear craters was rolling abrasion, independent of the temperature; ii) the temperature has an important effect on the behavior of the volume of wear and the coefficient of friction; and iii) with an increase in the temperature, a decrease in the volume of wear and the coefficient of friction was observed.

Wear Resistance of Ti-40Zr Alloy with TiN and ZrN Multilayer Coatings

Production and processing of titanium alloys are expensive and its alloys show low wear resistance. Substrates of Ti-40Zr, used for orthopedic implants, were obtained from the elemental mixture of hydrogenated powders, followed by a sequence of cold uniaxial and isostatic pressing and vacuum sintering. Aiming wear resistance increase, samples were coated by physical vapor deposition using electron beam technique (EB-PVD). Multilayer coatings with three different configurations were undertaken: Ti/TiN, Ti/TiN/ZrN and Ti/TiN/ZrN/TiN. Micro-abrasive wear tests were conducted by ball-cratering, with abrasive slurry of silicon carbide (SiC). The wear craters were measured at intervals corresponding to increments in the sliding distance of approximately 14 m. Range of the normal force were between 0.35 and 0,45 N. Scanning electron microscopy was used to evaluate the wear crater and the wear mode. All experiments showed three-body abrasive wear and a reduction of one order of magnitude in wear coefficient for two coated samples: 2,58∙10-12m³(Nm)-1to substrate, 5,4∙10-13m³(Nm)-1to Ti+TiN film and 7,22∙10-13m³(Nm)-1to Ti+TiN+ZrN film. In the Ti+TiN+ZrN+TiN experiment the wear coefficient of film is nearer to the substrate, 7,58∙10-13m³(Nm)-1. The multi-layers containing ZrN presented wear coefficient higher than Ti/TiN films, possibly due to existing residual stresses.

INFLUENCE OF DEEP CRYOGENIC TREATMENT AT ABRASIVE WEAR RESISTANCE IN ASTM 743 CA6NM

The Deep Cryogenic Treatment (DCT) has been used for improvement of steel mechanical properties, basically the abrasive wear resistance. At this work the cryogenic treatment at -190oC for 20 hours was applied, after conventional heat treatment, to improve its abrasive wear resistance. The specimens, divided in two groups, had been austenitized for forty five minutes at 965oC and 1065oC, respectively, then quenched in oil at room temperature. Afterwards they were tempered at 565oC for 90 minutes, and then cooled in air. Subsequently some samples were treated cryogenically, and some of them were submitted to a new cycle of tempering at 565oC for 90 minutes. The performed experiment included: hardness brinell, Xraydifratometry, metallography and micro-abrasive wear test. Variations in the microstructure with an improvement in the abrasive wear coefficient were found. These variations are probably a positive effect of the DCT on the samples microstructure. The microstructure were transformed from blocks of parallel lath martensite to small parallel or almost parallel packages of fine needles forming austenite. Traces of previous or retained austenite were found delimiting the grains. It is presumed that micro-carbide homogeneously distributed in the matrix and in the grain´s contours of the retained austenite was formed.

Mechanical and Tribological Characterization of TiB2 Thin Films

Titanium Diboride (TiB2) presents high mechanical and physical properties. Some wear studies were also carried out in order to evaluate its tribological properties. One of the most popular wear tests for thin films is the ball-cratering configuration. This work was focused on the study of the tribological properties of TiB2 thin films using micro-abrasion tests and following the BS EN 1071-6: 2007 standard. Due to high hardness usually patented by these films, diamond was selected as abrasive on micro-abrasion tests. Micro-abrasion wear tests were performed under five different durations, using the same normal load, speed rotation and ball. Films were deposited by unbalanced magnetron sputtering Physical Vapour Deposition (PVD) technique using TiB2 targets. TiB2 films were characterized using different methods as Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Spectroscopy (EDS), Atomic Force Microscopy (AFM), X-ray Diffraction (XRD), Electron Probe Micro-Analyser (EPMA), Ultra Micro Hardness and Scratch-test Analysis, allowing to confirm that TiB2 presents adequate mechanical and physical properties. Ratio between hardness (coating and abrasive particles), wear resistance and wear coefficient were studied, showing that TiB2 films shows excellent properties for tribological applications.

A study on friction coefficient and wear coefficient of coated systems submitted to micro-scale abrasion tests

Several works on friction coefficient during abrasive wear tests are available in the literature, but only a few were dedicated to the friction coefficient in micro-abrasive wear tests conducted with rotating ball. This work aims to study the influence of titanium nitride (TiN) and titanium carbide (TiC) coating hardness on the friction coefficient and wear coefficient in ball-cratering micro-abrasive wear tests. A ball of AISI 52100 steel and two specimens of AISI D2 tool steel, one coated with TiN and another coated with TiC, were used in the experiments. The abrasive slurry was prepared with black silicon carbide (SiC) particles and distilled water. Two normal forces and six sliding distances were defined, and both normal and tangential forces were monitored constantly during all tests. The movement of the specimen in the direction parallel to the applied force was also constantly monitored with the help of an electronic linear ruler. This procedure allowed the calculation of crater geometry, and thus the wear coefficient for the different sliding distances without the need to stop the test. The friction coefficient was determined by the ratio between the tangential and the normal forces, and for both TiN and TiC coatings, the values remained, approximately, in the same range (from μ=0.4 to μ=0.9). On the other hand, the wear coefficient decreased with the increase in coating hardness.