Adhesion Wear on Tool Rake and Flank Faces in Dry Cutting of Ti-6Al-4V

Titanium alloys are very chemically reactive and,therefore,have a tendency to weld to the cutting tool during machining.The deterioration in the tool life caused by adhesion is a serious problem when titanium alloys are cut using carbide tools.The chemical reactivity of titanium alloys with carbide tool materials and their consequent welding by adhesion onto the cutting tool during dry cutting leads to excessive chipping,premature tool failure,and poor surface finish.In the present study,dry turning and milling tests were carried out on Ti-6Al-4V alloys with WC?Co carbide tools.The adhesion on the tool rake and flank face was explored,the adhesive joint interface between the workpiece materials and tools were observed.SEM observation showed that adhesion can be observed both on the rake and the flank face,and was more pronounced in rake face than in flank face.There was evidence of element diffusion from the tool rake face to the adhering layer(vice versa) through the adhesive joint interface,which leads to the tool element loss and microstructure change.While the adhering materials at the flank face can be easily separated from the joint interface owing to the lower temperature and less pressure at the flank face,the adhesive wear attack results in an abrasive wear in the flank face.Moreover,adhesion is more notable in turning than in milling.The proposed research provides references for studying the adhesion between the workpiece materials and the tools,the adhesion mechanisms and their effect on the tool wear.

Adhesion Wear of Carbide Tool when Machining GH 907

The adhesion wear of cemented carbide tool when machining GH907 was studied with white light interferometer,infrared imaging,and SEM-EDS.The adhesion wear morphology,wear mechanism and the wear rule of adhesion were analyzed,and the effect of different cutting time and different cutting speed on adhesive wear were analyzed.The conclusion will provide useful references for the optimization of cutting parameters and the improvement of the tool life.

Effect of particulate reinforcement on wear behavior of magnesium matrix composites

The friction and wear behavior of magnesium matrix composites reinforced with particulate Mg2Si was characterized. The influence of Si, applied load and sliding rate on the wear behavior of Mg2Si/AM60 magnesium matrix composites was studied. The results indicate that the particulate Mg2Si can be synthesized by adding Si into magnesium alloy. The wear properties of AM60 magnesium alloy are significantly improved with MgzSi particles. The wear mass losses of AM60 magnesium alloy and MgaSi/AM60 magnesium matrix composites decrease with increase in applied load and sliding rate. The wear feature of the AM60 magnesium alloy is adhesion wear. The wear mechanism of Mg2Si/AM60 magnesium matrix composites transforms from abrasive wear to adhesion wear with the increase of load.

Microstructure,mechanical properties and dry wear resistance of β-type Ti-15Mo-xNb alloys for biomedical applications

In order to study the effect of element Nb on the microstructure and properties of the biomedical β-type Ti-Mo based alloys,Ti-15Mo-xNb（x=5,10,15 and 20 in %） alloys were investigated.The dry wear resistance of β-type Ti-15Mo-xNb alloys against Gr15 ball was investigated on CJS111A ball-disk wear instrument.Experimental results indicate that crystal structure and morphology of the Ti-15Mo-xNb alloys are sensitive to their Nb contents.Ti-15Mo-xNb alloys match those for β phase peaks and no any phases are found.The Vickers hardness values of all the Ti-15Mo-xNb alloys are higher than HV200.The compression yield strength of the Ti-15Mo-5Nb alloy is the lowest and that of the Ti-15Mo-10Nb alloy is the highest.For all the Ti-15Mo-xNb alloys,the friction coefficient is not constant but takes a higher value.In dry condition,SEM study reveals deep parallel scars on the wear surfaces of all the Ti-15Mo-xNb alloys under different loads.The friction coefficient of the Ti-15Mo-5Nb alloy under 1 N is the lowest.The wear principal mechanism for Ti-15Mo-xNb alloys is adhesive wear.

Tribological and wear performance of centrifuge cast functional graded copper based composite at dry sliding conditions

Non lubricated slide performance of functional grade copper matrix composite,fabricated using horizontal centrifuge cast technique was investigated using pin-on-disc tribo-tester.Rate of wear and friction coefficient of the inner wall thickness of hollow cylindrical cast specimen was analyzed using Taguchi based L27 orthogonal array,where the percentage of graphite particles were observed higher.Variable process parameters those influenced the rate of wear directly or indirectly were:applied load(15,25 and 35 N),slide velocity(1.5,2.5 and 3.5 m/s)and slide distance(750,1500 and 2250 m).Rate of wear and friction coefficient showed a proportional dependency with applied load and slide distance,whereas showing a decline during intermediate slide velocity.Signal-to-Noise ratio predicted the minimal tribo-condition,on‘smaller-the-better’basis.Analysis of Variance technique quantified the influence of affecting parameters,along with their interactions.Regression analysis was utilized for the validation of the experimental data.Micrographs and scanning electron microscopy exhibited the wear mechanisms and mechanically mixed layer formation during worn surfaces analysis.

Effect of reinforcement content on the adhesive wear behavior of Cu10Sn5Ni/Si3N4 composites produced by stir casting

The main objective of this paper was to fabricate CuSnNi alloy and its composites reinforced with various contents of SiNparticles(5wt%, 10wt%, and 15wt%) and to investigate their dry sliding wear behavior using a pin-on-disk tribometer. Microstructural examinations of the specimens revealed a uniform dispersion of SiNparticles in the copper matrix. Wear experiments were performed for all combinations of parameters, such as load(10, 20, and 30 N), sliding distance(500, 1000, and 1500 m), and sliding velocity(1, 2, and 3 m/s), for the alloy and the composites. The results revealed that wear rate increased with increasing load and increasing sliding distance, whereas the wear rate decreased and then increased with increasing sliding velocity. The primary wear mechanism encountered at low loads was mild adhesive wear, whereas that at high loads was severe delamination wear. An oxide layer was formed at low velocities, whereas a combination of shear and plastic deformation occurred at high velocities. The mechanism at short sliding distances was ploughing action of SiNparticles, which act as protrusions; by contrast, at long sliding distances, direct metal–metal contact occurred. Among the investigated samples, the Cu/10wt% SiNcomposite exhibited the best wear resistance at a load of 10 N, a velocity of 2 m/s, and a sliding distance of 500 m.

Characteristics of microstructure and performance of laser-treated electroless Ni-P/Ni-W-P duplex coatings

Characteristics of microstructures of electroless Ni-P/Ni-W-P duplex coatings were investigated using SEM/EDX and XRD analysis techniques. Microhardness and wear behaviour of the coatings before and after laser crystallization were evaluated by measurements of hardnesses of coating surface and cross-section, and by unlubricated friction and wear experiments. The results indicate that it is possible to prepare electroless Ni-P/Ni-W-P duplex coatings by sequential immersion in two different plating baths. After laser crystallization, the microstructures of electroless Ni-P/Ni-W-P duplex coatings present the characteristics of higher degree of crystallization and larger grain size for outer layer Ni-W-P than inner Ni-P, but outer layer has a higher hardness. The wear resistance of laser-treated duplex coatings in a given process parameter conditions is superior to the as-plated ones. Laser treatment was performed directly in air without argon protection, which provides the possibility for application of industrialized production.

Electrochemically-stimulated nanoscale mechanochemical wear of silicon

Mechanochemical reactions at the sliding interface between a single-crystalline silicon(Si)wafer and a silica(SiO2)microsphere were studied in three environmental conditions:humid air,potassium chloride(KCl)solution,and KCl solution with an applied voltage.Compared to that from humid air,mechanochemical material removal from the silicon surface increased substantially in the KCl-immersed condition,and further increased when electrochemistry was introduced into the tribological system.By measuring the load dependence of the material removal rate and analyzing the results using a mechanically assisted Arrhenius-type kinetic model,the activation energy(E_(a))and the mechanical energy(E_(m)),by which this energy is reduced by mechanical activation,were compared qualitatively under different environmental conditions.In the KCl-immersed condition,mechanochemistry may decrease the required effective energy of reactions(E_(eff)=E_(a)−E_(m))and promote material removal mainly through improved catalysis of the mechanochemical reactions facilitated by greater availability of water molecules compared to the humid air condition.Thus,the effectiveness of the mechanochemistry is improved.In the electrochemical condition,electrochemically-accelerated oxidation of the silicon surface was confirmed by the X-ray photoelectron spectroscopy(XPS)characterization.The results strongly suggest that electrochemistry further stimulates mechanochemical reactions primarily by increasing the initial energy state of the surface via the facilitated formation of interfacial bonding bridges,i.e.,a surface oxidation/hydroxylation process.

Fretting wear behaviour of high-nitrogen stainless bearing steel under lubrication condition

The fretting wear performance of high-nitrogen stainless bearing steel(40Cr15Mo2VN)under lubrication conditions was researched.Lithium-based grease was preparedusing MoS2 and carbon nanotubes(CNTs)as additives.AISI 52100 steel ball was used in four-ball test to evaluate the extreme pressure property and wear resistance of grease.After four-ball test,the grease adding 0.8 mass%MoS2 and 0.8 mass%CNTs,respectively,was chosen and used for fretting test.AISI 52100 ball and 40Cr15Mo2VN steel disc were used as the upper and lower samples for fretting test.The results showed that wear power consumption increased with the increase in both sliding velocity and contact stress.When initial contact stress was 2.047 GPa,the main wear mechanisms were abrasive wear and plastic deformation as the velocity increased 0.028 to 0.112 m/s.When the velocity was 0.028 m/s,the main wear mechanisms changed abrasive wear to adhesion wear and finally to abrasive wear and adhesion wear as the initial contact stress increased 1.788 to 2.579 GPa.The volume loss grew sharply becaof the changes in wear mechanisms.In this condition,the volume loss growth rate can be divided into three regions according to different wear power consumption ranges corresponding to different wear mechanisms.

Coupling behavior between adhesive and abrasive wear mechanism of aero-hydraulic spool valves

Leakage due to wear is one of the main failure modes of aero-hydraulic spool valves. This paper established a practical coupling wear model for aero-hydraulic spool valves based on dynamic system modelling theory. Firstly, the experiment for wear mechanism verification proved that adhesive wear and abrasive wear did coexist during the working process of spool valves. Secondly coupling behavior of each wear mechanism was characterized by analyzing actual time-variation of model parameters during wear evolution process. Meanwhile, Archard model and three-body abrasive wear model were utilized for adhesive wear and abrasive wear, respectively. Furthermore, their coupling wear model was established by calculating the actual wear volume. Finally, from the result of formal test, all the required parameters for our model were obtained. The relative error between model prediction and data of pre-test was also presented to verify the accuracy of model, which demonstrated that our model was useful for providing accurate prediction of spool valve's wear life. (C) 2016 The Authors. Production and hosting by Elsevier Ltd. on behalf of Chinese Society of Aeronautics and Astronautics.

Adhesive wear mechanisms uncovered by atomistic simulations

In this review, we discuss our recent advances in modeling adhesive wear mechanisms using coarse-grained atomistic simulations. In particular, we present how a model pair potential reveals the transition from ductile shearing of an asperity to the formation of a debris particle. This transition occurs at a critical junction size, which determines the particle size at its birth. Atomistic simulations also reveal that for nearby asperities, crack shielding mechanisms result in a wear volume proportional to an effective area larger than the real contact area. As the density of microcontacts increases with load, we propose this crack shielding mechanism as a key to understand the transition from mild to severe wear. We conclude with open questions and a road map to incorporate these findings in mesoscale continuum models. Because these mesoscale models allow an accurate statistical representation of rough surfaces, they provide a simple means to interpret classical phenomenological wear models and wear coefficients from physics-based principles.

Adhesive and corrosive wear at microscales in different vapor environments

Adhesive and corrosive wear at microscales are quantitatively distinguished in lifetime tests of resonant bulk-fabricated silicon microelectromechanical systems(MEMS).By analyzing the oscillation decay characteristics in different vapor environments,we find that wear is dominated by asperity adhesion during the initial stages of rubbing in dry N2 or O2/N2 mixtures;in these situations the transient wear rate is inversely proportional to the wear depth.But in water or ethanol vapors,chemical reactions between the corrosive adsorbed layer and the silicon substrate limit the wear rate to a constant.These observations are consistent with atomic explanations.The differences between adhesive and corrosive wear explain the advantages offered by lubricating with alcohol vapors rather than using dry environments for tribo-MEMS devices.Compared to ethanol,the relatively poor anti-wear effect of water vapor is explained by aggressive and rapid tribo-reactions.

Influence of graphene nanoplatelets on mechanical properties and adhesive wear performance of epoxy-based composites

Epoxy resin is one of the most widely used thermoset polymers in high-performance composite materials for lightweight applications.However,epoxy has a high coefficient of friction,which limits its tribological applications.In this study,the effect was investigated of different weight fractions of solid lubricant graphene nanoplatelets(GNPs),ranging from 0 to 4.5 wt%,on mechanical and adhesive wear performance of epoxy.Adhesive wear tests covered mild and severe wear regimes.The correlation of tribological and mechanical properties was studied as well.Scanning electron microscopy(SEM)was used to observe the failure mechanisms for both tribological and mechanical samples after each test.The results revealed that the addition of GNPs to the epoxy improved its stiffness and hardness but reduced its fracture strength and toughness.Adhesive wear performance exhibited high efficiency with GNP additions and showed reductions in the specific wear rate,the coefficient of friction,and the induced interface temperature by 76%,37%,and 22%,respectively.A fatigue wear mechanism was predominant as the applied load increased.Most importantly,severe wear signs occurred when the interface temperature reached the heat distortion temperature of the epoxy.The tribological,and mechanical properties showed only a weak correlation to each other.The addition of GNPs to epoxy by less than 4.5 wt%was highly efficient to improve the wear performance while maintaining the fracture strength and toughness.Fourier transform infrared spectroscopy(FTIR)analysis shows no chemical interaction between the epoxy matrix with GNPs,which implies its physical interaction.

An advanced efficient model for adhesive wear in elastic-plastic spherical contact

A finite element(FE)model combining submodel technique is presented for the adhesive wear in elastic–plastic spherical contact.It consists of a global model,showing the potential location of fracture under combined normal and tangential loading,and a refined mesh submodel covering only the region near the potential fracture.This allows to describe the morphology of wear particle more accurately than that in a previously developed model by the authors.A range of normal loading is studied to show its effect on the shape and volume of wear particles.Two main regimes of mild and severe wear(along with a relatively narrow transition region between them)are found,which show almost linear and power-law dependency of wear rate on normal loading,respectively.Such behavior agrees with published experimental observations.However,the transition region is theoretically predicted here for the first time.

Tribological performance of TiAlSiN and TiAlCrN/TiAlN coating blades

A new laboratory evaluation method for the coating blade was developed, and the tribological properties of coating blades with different Ti-based coatings were studied by UMT-2 tribometer. Comparison between the areas of scratches before and after the cutting experiment was used to evaluate the cutting performance of the blades. Results showed that friction coefficient of TiA1CrN/TiA1N coating was significantly lower than that of TiA1SiN coating. Analysis of the worn surface revealed that the TiA1SiN and TiAICrN/TiA1N coatings in the dry turning process exhibited sign of inhornogeneous adhesive wear and abrasive wear. TiA1CrN/TiA1N coating has a longer working life and better anti-wear property because of its duplex coating.

Microstructural evolution of Al-Si coating and its influence on high temperature tribological behavior of ultra-high strength steel against H13 steel

Al-Si coated ultra-high strength steel（UHSS）has been commonly applied in hot stamping process.The influence of austenitizing temperature on microstructure of Al-Si coating of UHSS during hot stamping process and its tribological behavior against H13 steel under elevated temperature were simulatively investigated.The austenitizing temperature of Al-Si coated UHSS and its microstructual evolution were confirmed and analyzed by differential scanning calorimetry and scanning electron microscopy.A novel approach to tribological testing by replicating hot stamping process temperature history was presented.Results show that the hard and stable phases Fe_2Al_5＋FeAl_2 formed on Al-Si coating surface after exposure to 930°C for 5 min,which was found to be correlated to the tribological behavior of coating.The friction coefficient of coated steel was more stable and higher than that of uncoated one.The main wear mechanism of Al-Si coated UHSS was adhesion wear,while abrasive wear was dominant for the uncoated UHSS.

Effect of vanadium addition on microstructure and properties of AI_(0.5)Cr_(0.9)FeNi_(2.5)multi-principal alloys

AI_(0.5)Cr_(0.9)FeNi_(2.5)V_(x)(x=0,0.2,0.4,0.6,0.8,1.0)multi-principal alloys were prepared by vacuum arc melting.The effect of vanadium addition on its microstructure and properties was investigated.The results show that the alloys of all components exhibited an FCC single-phase structure.With the addition of vanadium,the microstructure of the alloy changed from dendrites to equiaxed crystals,the grains were remarkably refined,and the layered CrV phase was exhibited,which improved the properties of the alloy.The yield strength of the alloy was slightly improved,and the alloys with various components presented good plasticity.When V content reached 0.8,the yield strength was 600 MPa,and no fracture occurred.Friction-wear testing showed that the wear debris was reduced with the addition of V element.The sample with V element content of 0.4 had the best friction and wear performance.The surface grooves became shallow,the worn debris was less,and the wear mechanism was mainly abrasive wear.The polarisation curve showed that the alloy with V element content of 0.2 has the best corrosion resistance.The passivation interval reached 900 mV.The corrosion potential and the corrosion current density were-496.299 mV and 2.759μA/cm^(2),respectively.

Investigation into the tribological behaviors of press hardening steels on the tailored conditions

There has been a growing demand for safety parts with tailored properties in automobile industry.However,the understanding of tribological behavior of press hardening steels(PHS)on the tailored conditions is highly inadequate.The present work aims at creating new knowledge about the tribological characteristics of PHS on the tailored conditions and bridging this existing gap.The paper proposes an improved hot drawing tribo-simulator to simulate the realistic experimental conditions industry.Investigations were carried out on the condition of different initial heating temperatures,tool temperatures,austenitizing temperatures,cooling rates and microstructures.The presented results show that the whole frictional process is divided into three stages for both coated and uncoated steels.The frictional factor changes a lot and the peak value of frictional factor occurs for serious adhesive wear.The frictional factor rises as the tool temperature and austenitizing temperature rise.The surface morphology of tools indicates that the coating adhering to tool gets thicker as the tool temperature increases.With the increase of cooling rate,the frictional factor declines firstly and then rises to some extent.Flat dies with different temperatures are used to form specimens with different microstructures,which also affects the frictional factor and wear.