Microstructure and wear mechanisms of OCTG chasers

The wear mechanism and tool life of four types of oil country tubular goods chasers are studied herein via metallographic microscopy,scanning electron microscopy,and energy dispersive spectroscopy.Results show that when the tool has a fine and uniform microstructure,the main failure mode is wear failure.Furthermore,observed phenomena including large chip bonding,coating peeling,cracks demonstrate that the main wear mechanisms of the tool are adhesive wear,abrasive wear,coating flaking,and microchipping.

A Review on Fretting Wear Mechanisms,Models and Numerical Analyses

Fretting wear is a material damage in contact surfaces due to micro relative displacement between them.It causes some general problems in industrial applications,such as loosening of fasteners or sticking in components supposed to move relative to each other.Fretting wear is a complicated problem involving material properties of tribosystem and working conditions of them.Due to these various factors,researchers have studied the process of fretting wear by experiments and numerical modelling methods.This paper reviews recent literature on the numerical modelling method of fretting wear.After a briefly introduction on the mechanism of fretting wear,numerical models,which are critical issues for fretting wear modelling,are reviewed.The paper is concluded by highlighting possible research topics for future work.

High-temperature wear mechanisms of TiNbWN films:Role of nanocrystalline oxides formation

Réfractory high/medium entropy nitrides(HENs/MENs)exhibit comprehensive application prospects as protective films on mechanical parts,particularly those subjected to sliding contacts at elevated temperatures.In this study,a new MEN system TiNbWN,forming a single fc solution,is designed and its wear performance at temperatures ranging from 25 to 750℃is explored.The wear mechanisms can be rationalized by examining the subsurface microstructural evolutions using the transmission electron microscopy as well as calculating the phase diagrams and interfacial adhesion behavior employing calculation of phase diagram(CALPHAD)and density functional theory(DFT).To be specific,increased wear losses occur in a temperature range of 25-600℃,being predominantly caused by the thermally-induced hardness degradation;whereas at the ultimate temperature(750℃),the wear loss is refrained due to the formation of nanocrystalline oxides(WnO_(3n-2r)TiO_(2),and TiOx),as synergistically revealed by microscopy and CALPHAD,which not only enhance the mechanical properties of the pristine nitride film,but also act as solid lubricants,reducing the interfacial adhesion.Thus,our work delineates the role of the in situ formed nanocrystalline oxides in the wear mechanism transition of TiNbWN thin films,which could shed light on the high-temperature wear behavior of refractory HEN/MENfilms.

Effect of Ni content on the wear behavior of Al-Si-Cu-Mg-Ni/SiC particles composites

In recent years,the addition of Ni has been widely acknowledged to be capable of enhancing the mechanical properties of Al-Si alloys.However,the effect of Ni on the wear behaviors of Al-Si alloys and Al matrix composites,particularly at elevated temperat-ures,remains an understudied area.In this study,Al-Si-Cu-Mg-Ni/20wt%SiC particles(SiCp)composites with varying Ni contents were prepared by using a semisolid stir casting method.The effect of Ni content on the dry sliding wear behavior of the prepared compos-ites was investigated through sliding tests at 25 and 350℃.Results indicated that theθ-Al_(2)Cu phase gradually diminished and eventually disappeared as the Ni content increased from 0wt%to 3wt%.This change was accompanied by the formation and increase inδ-Al_(3)CuNi andε-Al_(3)Ni phases in microstructures.The hardness and ultimate tensile strength of the as-cast composites improved,and the wear rates of the composites decreased from 5.29×10^(−4)to 1.94×10^(−4)mm^(3)/(N∙m)at 25℃and from 20.2×10^(−4)to 7×10^(−4)mm^(3)/(N∙m)at 350℃with the increase in Ni content from 0wt%to 2wt%.The enhancement in performance was due to the presence of strengthening network structures and additional Ni-containing phases in the composites.However,the wear rate of the 3Ni composite was approximately two times higher than that of the 2Ni composite due to the fracture and debonding of theε-Al_(3)Ni phase.Abrasive wear,delamination wear,and oxidation wear were the predominant wear mechanisms of the investigated composites at 25℃,whereas delamination wear and oxid-ation wear were dominant during sliding at 350℃.

TOOL WEAR PATTERNS AND MECHANISMS OF SOLID CEMENTED CARBIDE IN HIGH-SPEED MILLING OF ALUMINUM ALLOY

The wear patterns and wear mechanisms of solid cemented carbide are analyzed in high-speed milling of aluminum alloy. Results show that the dominant wear patterns are coating damage, crater wear, micro-chipping, breakage, and so on. The main wear mechanisms are adhesion, diffusion and fatigue. Compared with conventional speed machining, the effect and impact of thermal-dynamical coupling field play an important role in the cutting tool wear in high-speed milling of aluminum alloy.

Tool wear mechanisms in the machining of Nickel based super-alloys： A review

Nickel based super-alloys are widely employed in aircraft engines and gas turbines due to their high temperature strength, corrosion resistance and, excellent thermal fatigue properties. Conversely, these alloys are very difficult to machine and cause rapid wear of the cutting tool, frequent tool changes are thus required resulting in low economy of the machining process. This study provides a detailed review of the t0ol wear mechanism in the machining of nickel based super-alloys. Typical tool wear mechanisms found by different researchers are analyzed in order to find out the most prevalent wear mechanism affecting the tool life. The review of existing works has revealed interesting findings about the tool wear mechanisms in the machining of these alloys. Adhesion wear is found to be the main phenomenon leading to the cutting tool wear in this study.

Wear mechanisms and hardness thresholds under repeated impact contact loading

Experiments were performed on 20 different types of materials to analyze the impact contact wear and to establish the wear mechanism map, The wear mechanism has been categorized into three prominent regions （delamination wear, quasi-nano wear and lamination-like wear） and is governed by two hardness thresholds （Hdq and Hql）. When the material hardness gcp〈Hdq, the delamination wear is the dominant wear mechanism; when Hcp〉Hql, the mechanism is lamination-like wear; however, whenHco is between Hdq and Hql, the mechanism is determined to be quasi-nano wear. Hdq is determined to be the threshold hardness between delamination wear and quasi-nano wear that reflects the cracks being produced in the subsurface layer, whereas, Hql is termed threshold hardness between quasi-nano wear and lamination-like wear with formation of nanostructure within the surface layer.

Corrosion and wear properties of in situ(TiB+TiC)/TA15 composites with a high volume percentage of reinforcement

The in situ(TiC+TiB)/TA15 composites with different volume percentages of reinforcement(10%,15%,20%and 25%)were prepared by water-cooled copper crucible vacuum suspension melting technology.The structures and compositions of the TA15 alloy and its composites were analyzed by XRD and EDS,and their electrochemical corrosion behaviors in the 3.5%NaCl solution were studied.Corrosion wear testing was conducted using a reciprocating ball-on-disc wear tester under a 10 N load.Results show that the in situ fibrous TiB phase and the granular TiC phase are uniformly distributed on the composite matrix.The microhardness can reach up to 531 HV as 25vol.%TiC+TiB reinforcement is added.Compared with the TA15 alloy,the volume wear rate decreases from(2.21±0.07)×10^(-4)to(1.75±0.07)×10^(-4)mm^(3)·N^(-1)·m^(-1)by adding 15vol.%TiC+TiB reinforcement,and the wear mechanism is adhesive wear.When the volume percentage of the reinforcement phase reaches 25%,the volume wear rate increases from(1.75±0.07)×10^(-4)to(2.41±0.07)×10^(-4)mm^(3)·N^(-1)·m^(-1),and the wear mechanism changes into abrasive wear.The volume loss resulted by the interaction between corrosion and wear accounts for more than 27%of the total wear volume.The volume loss due to wear-induced corrosion changes from 1.94%to 4.06%with different additions of reinforcement.The volume loss caused by corrosion-induced wear initially increases from 24.08%to 26.90%as the reinforcement increases from 0 to 15%due to the increase of corrosion potential,and then decreases from 26.90%to 25.68%as the reinforcement increases from 15%to 25%due to the peeling of TiC phase.

Wear mechanism and serious wear position of casing pipe in vertical backfill drill-hole

Vertical backfill drill-hole is usually a key project in an underground mine with backfill method and can be easily damaged by impact of backfill slurry.Observation of the damaged vertical backfill drill-holes in Jinchuan Nonferrous Metal Corporation（JNMC）,Gansu Province,China,given by a digital drill-hole video camera,indicated that there usually exist serious wear zones in casing pipe in vertical backfill drill-hole（CVBH）.It was suggested that serious wear position of CVBH should be located at an interface between air and solid-liquid mixture within CVBH.Backfill slurry falls freely and impacts the wall of CVBH near the interface with great momentum and energy coming from high speed free fall of backfill slurry.The depth of serious wear position of CVBH,i.e.,free fall height of backfill slurry in CVBH,can be estimated by the height of vertical backfill drill-hole,the length of horizontal pipeline,the density of slurry and the hydraulic gradient of pipeline system.A case study indicated that the estimation equation of serious damage depth of CVBH was of enough accuracy and was helpful for daily maintenance and management of vertical backfill drill-hole.

Effect of nitrogen ion implantation dose on torsional fretting wear behavior of titanium and its alloy

Various doses of nitrogen ions were implanted into the surface of pure titanium, Ti6Al7Nb and Ti6Al4V, by plasma immersion ion implantation. Torsional fretting wear tests involving flat specimens of no-treated and treated titanium, as well as its alloys, against a ZrO2 ball contact were performed on a torsional fretting wear test rig using a simulated physiological medium of serum solution. The treated surfaces were characterized, and the effect of implantation dose on torsional fretting behavior was discussed in detail. The results showed that the torsional fretting running and damage behavior of titanium and its alloys were strongly dependent on the dose of the implanted nitrogen ions and the angular displacement amplitude. The torsional fretting running boundary moved to smaller angular displacement amplitude, and the central light damage zone decreased, as the ion dose increased. The wear mechanisms of titanium and its alloys were oxidative wear, abrasive wear and delamination, with abrasive wear as the most common mechanism of the ion implantation layers.

Dry sliding friction and wear behaviors of Mg_2B_2O_5 whisker reinforced 6061Al matrix composites

The friction and wear properties of Mg2B2O5 whisker reinforced 6061Al matrix composite fabricated via power ultrasonic-stir casting process were investigated using a ball-on-disk wear-testing machine against a GCr45 steel counterface under dry sliding conditions. The reinforcements include as-received Mg2B2O5 whiskers and Mg2B2O5 whiskers coated with CuO and ZnO. The volume fraction of the composites is 2%. The relationship between the wear rate and the coefficient of friction was discussed. The results indicate that the wear rate of the Mg2B2O5 whiskers coated with ZnO reinforced aluminum matrix composites is the lowest among the materials. As the applied load and sliding speed steadily increase the coefficients of friction and wear rates of the as-received matrix alloy and the fabricated composites decrease. As the applied load and sliding speed increase, the wear mechanisms of the composites shift from a mild to a severe regime.

Dry sliding wear behavior and mechanism of AM60B alloy at 25-200 ℃

Dry wear tests under atmospheric conditions at 25-200 °C and loads of 12.5-300 N were performed for AM60B alloy. The wear rate increases with increasing the load; the mild-to-severe wear transitions occur under the loads of 275 N at 25 °C, 150 N at 100 °C and 75 N at 200 °C, respectively. However, as the load is less than 50 N, the wear rate at 200 °C is lower than that at 25 °C or 100 °C. In mild wear regimes, the wear mechanisms can be classified into abrasive wear, oxidation wear and delamination wear. Delamination wear prevailed as the mild-to-severe wear transition starts to occur; the delamination occurs from the inside of matrix. Subsequently, plastic-extrusion wear as severe wear prevails accompanied with the transition. The thick and hard tribo-layer postpones the mild-to-severe wear transition due to restricting the occurrence of massive plastic deformation of worn surfaces.

Friction and wear behaviors of Nb-Ti-Si-Cr based ultrahigh temperature alloy and its Zr-Y jointly modified silicide coatings

Zr-Y jointly modified silicide coatings were prepared on an Nb-Ti-Si-Cr based ultrahigh temperature alloy by pack cementation process. The wear behaviors of both the base alloy and coatings were comparatively studied at room temperature and 800 ℃ using SiC balls as the counterpart. The Zr-Y jointly modified silicide coating is mainly composed of a thick （Nb,X）Si2 outer layer and a thin （Ti,Nb）5Si4 inner layer. The coatings possess much higher microhardness than the base alloy. The wear rates of both the base alloy and coatings increase with increasing the sliding loads. However, the coatings have much lower wear rates than the base alloy under the same sliding conditions. The coatings have superior anti-friction property, and can provide effective protection for the base alloy at both room temperature and 800 ℃ in air.

Dual motion fretting wear behaviors of titanium and its alloy in artificial saliva

A dual motion combined by radial and tangential fretting was achieved on a modified hydraulic fretting wear test rig. The dual motion fretting tests of medical pure titanium （TA2） and Ti6Al7Nb alloy in artificial saliva were carried out under varied contact inclined angles （45° and 60°）, and the maximum imposed load varied from 200 to 400 N at a constant loading speed of 6 mm/min. The effects of the cyclic vertical force and the inclined angle were investigated in detail. Dynamic analysis in combination with microscopic examinations shows that the wear scar and plastic deformation accumulation present a strong asymmetry. The Ti6Al7Nb has better wear resistance than TA2 in artificial saliva at the same test parameters, and with the increase of inclined angle and decrease of imposed load, the wear reduces accordingly. The wear mechanisms of pure titanium TA2 and Ti6Al7Nb alloy under the condition of dual motion fretting in artificial saliva are abrasive wear, oxidative wear and delamination.

Wear behavior of Mg-10Y-4Gd-1.5Zn-0.4Zr alloy

Dry sliding wear tests were performed on a Mg-10Y-4Gd-1.5Zn-0.4Zr alloy using a Ball-on-Flat type wear apparatus against an AISI 52100 type bearing steel ball counterface. The wear rates were measured within a load range of 3-25 N, a sliding speed range of 0.03-0.3 m/s and a sliding temperature range of 25-200 ℃ at a constant sliding distance of 400 m. The morphologies of the worn surfaces and wear debris were studied by scanning electron microscopy （SEM） and energy dispersive X-ray spectroscopy （EDS）. Comparatively, the wear properties of a hypereutectic Al-Si aluminium alloy under the same condition were measured. The results indicate that the wear rates of Mg-10Y-4Gd-1.5Zn-0.4Zr alloy are lower than that of cast＋T6 AC9B aluminium alloy. The dominant mechanism of cast＋T6 Mg-10Y-4Gd-1.5Zn-0.4Zr alloy is abrasion wear mixed with other wear mechanisms, which tends to be an abrasion and plastic deformation wear at high normal load such as 10-25 N, abrasion and plastic deformation wears with small participation of delamination and oxidative wears at high sliding speed such as 0.12-0.3 m/s, and an oxidative and abrasion wear at high test temperature such as 100-200 ℃. The Mg12Y1Zn1 phase in Mg-10Y-4Gd-1.5Zn-0.4Zr alloy plays an important role in the wear rate.

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.

Dry sliding wear behavior of rheocast hypereutectic Al-Si alloys with different Fe contents

The effect of iron content on wear behavior of hypereutectic Al?17Si?2Cu?1Ni alloy produced by rheocasting process was investigated. The dry sliding wear tests were carried out with a pin-on-disk wear tester. The results show that the wear rate of the rheocast alloy is lower than that of the alloy produced by conventional casting process under the same applied load. The fine particle-likeδ-Al4(Fe,Mn)Si2 and polygonalα-Al15(Fe,Mn)3Si2 phases help to improve the wear resistance of rheocast alloys. As the volume fraction of fine Fe-bearing compounds increases, the wear rate of the rheocast alloy decreases. Moreover, the wear rate of rheocast alloy increases with the increase of applied load from 50 to 200 N. For the rheocast alloy with 3% Fe, oxidation wear is the main mechanism at low applied load (50 N). At higher applied loads, a combination of delamination and oxidation wear is the dominant wear mechanism.

Investigation on dry sliding wear behavior of Mg/BN nanocomposites

The present research objective is to investigate the effect of boron nitride nanoparticles reinforcement on dry sliding wear behavior of pure Magnesium and magnesium nanocomposites.The fabricated nanocomposites contains varied percentages of boron nitride such as 0%(pure Mg),0.5%,1.5%and 2.5%were synthesized by using powder metallurgy technique and followed by a hot working process called hot extrusion.The pin on disk equipment was used for conducting the wear tests for traditional loads of 5 N,7 N and 10 N at different sliding speeds of 0.6,0.9 and 1.2 m/s against the steel disk at room temperature.For all traditional loads and sliding speeds,the changes in wear rate and friction co-efficient(μ)with respect to sliding distances were observed and analyzed.The wear characteristics are observed with the help of scanning electron microscopy under given test conditions.To investigate dominant wear mechanisms for various test conditions,the morphologies of all worn composites surfaces were analyzed.Final results show that,for all nanocomposites the wear level raises with respect to the sliding speeds and loads.Magnesium reinforced with 0.5%boron nitride shows lower wear rates and low friction coefficient values compare with magnesium reinforced with 1.5%boron nitride and 2.5%boron nitride nanocomposites.

Wear Performance of Laser Surface Hardened GCr15 Steel

In order to assess the new tribological properties of laser surface hardened GCr15 steel, the wear resistance between specimens treated with laser and those of conventionally hardened under dry sliding conditions was compared. The change of wear mechanisms in laser hardened GCr15 resulted in a distinct difference in wear rates. The results showed that quenched zones not only had sufficient depth of hardening and higher hardness, but had more retained austenite and finer carbides because of a higher degree of carbide dissolution. Laser surface hardened GCr15 steel specimens exhibited superior wear resistance to their conventionally hardened specimens due to the effects of the microstructure hardening, high hardness and toughness. The wear mechanism for both the laser quenched layer and conventionally hardened layer was highly similar, generally involving adhesive, material transfer, wear-induced oxidation and plowing. When conventionally hardened block specimens rubbed against the laser hardened specimens, the surface of conventionally hardened block specimens was polished. The microstructural thermal stability was increased after laser surface treatment.

Friction and Wear Behaviors of MoS_2/Zr Coated HSS in Sliding Wear and in Drilling Processes

MoS2 metal composite coatings have been successful used in dry turning, but its suitability for dry drilling has not been yet established. Therefore, it is necessary to study the friction and wear behaviors of MoS2/Zr coated HSS in sliding wear and in drilling processes. In the present study, MoS2/Zr composite coatings are deposited on the surface of W6Mo5Cr4V2 high speed steel（HSS）. Microstructural and fundamental properties of these coatings are examined. Ball-on-disc sliding wear tests on the coated discs are carried out, and the drilling performance of the coated drills is tested. Test results show that the MoS2/Zr composite coatings exhibit decreases friction coefficient to that of the uncoated HSS in sliding wear tests. Energy dispersive X-ray（EDX） analysis on the wear surface indicates that there is a transfer layer formed on the counterpart ball during sliding wear processes, which contributes to the decreasing of the friction coefficient between the sliding couple. Drilling tests indicate that the MoS2/Zr coated drills show better cutting performance compared to the uncoated HSS drills, coating delamination and abrasive are found to be the main flank and rake wear mode of the coated drills. The proposed research founds the base of the application of MoS2 metal composite coatings on dry drilling.