The tribological characteristics of TiCN coating at elevated temperatures

The tribological behaviour of TiCN coating prepared by unbalanced magnetron sputtering is studied in this work. The substrates made from austenitic steel were coated by TiCN coatings during one deposition. The measurements were provided by high temperature tribometer (pin-on-disc, CSM Instruments) allowing measuring the dependency of friction coefficient on cycles (sliding distance) up to 500 °C. The evolution of the friction coefficient with the cycles was measured under different conditions, such as temperature or sliding speed and the wear rate of the ball and coating were evaluated. The 100Cr6 balls and the Si₃N₄ ceramic balls were used as counter-parts. The former were used at temperatures up to 200 °C, the latter up to 500 °C. The wear tracks were examined by optical methods and SEM. The surface oxidation at elevated temperatures and profile elements composition of the wear track were also measured.The experiments have shown considerable dependency of TiCN tribological parameters on temperature. Rise in temperature increased both friction coefficient and the wear rate of the coating in case of 100Cr6 balls. The main wear mechanism was a mild wear at temperatures up to 200 °C; fracture and delamination were dominating wear mechanisms at temperatures from 300 to 500 °C.     

Characterization and tribological investigation of sol–gel ceramic films on Ti–6Al–4V

SiO₂, TiO₂, and hydroxyapatite (HA) thin films with good biocompatibility were grown on Ti–6Al–4V (coded as TC4) substrate by sol–gel and dip-coating processes from specially formulated sols, followed by annealing at 500 °C The chemical states of some typical elements in the target films were detected by means of X-ray photoelectron spectroscopy (XPS). Atomic force microscopy (AFM) and high-resolution scanning electron microscopy (SEM) are applied to characterize the original unworn films. The tribological properties of thin films sliding against an AISI52100 steel ball were evaluated on a reciprocating friction and wear tester. As the result, the target films composed of nano-particles ranging from 30 nm to 100 nm around were obtained. All the sol–gel ceramic films are superior in resisting wear compared with the TC4 substrate. Among all, HA film shows the best resistance while SiO₂ film shows the worst wear resistance both under higher (3 N) and lower load (1 N). TiO₂ shows good wear resistance under lower load (1 N). SEM observation of the morphologies of worn surfaces indicates that the wear of TC4 is characteristic of abrasive wear. Differently, abrasion, plastic deformation and micro-fracture dominate the wear of ceramic films. The superior friction reduction and wear resistance of HA film is greatly due to the slight plastic deformation of the film. It is supposed that the deformation of the HA film is closely related to the special arrangement of the nano-particles and microstructure. HA film is recommended for clinical application from the point of wear resistance view.     

Mechanical and unlubricated tribological properties of titanium-containing diamond-like carbon coatings

Titanium-containing diamond-like carbon (Ti-DLC) coatings were deposited on steel with a close-field unbalanced magnetron sputtering in a mixed argon/acetylene atmosphere. The morphology and structure of Ti-DLC coatings were investigated by scanning electron microscopy, transmission electron microscopy, atomic force microscopy and Raman spectroscopy. Nanoindentation, nanoscratch and unlubricated wear tests were carried out to evaluate the hardness, adhesive and tribological properties of Ti-DLC coatings. Electron microscopic observations demonstrated the presence of titanium-rich nanoscale regions surrounded by amorphous carbon structures in Ti-DLC coating. The Ti-DLC coatings exhibit friction coefficients of 0.12–0.25 and wear rates of 1.82 × 10^?9 to 4.29 × 10^?8 mm³/Nm, depending on the counterfaces, sliding speed and temperature. The Ti-DLC/alumina tribo-pair shows a lower friction coefficient than the Ti-DLC/steel tribo-pair under the identical wear conditions. Increasing the test temperature from room temperature to 200 °C reduces the coefficient of friction and, however, clearly increases the wear rate of Ti-DLC coatings. Different wear mechanisms, such as surface polishing, delamination and tribo-chemical reactions, were found in the tribo-contact areas, depending on different wear conditions.     

Abrasive wear behavior of boronized AISI 8620 steel

In this study, AISI 8620 steel was boronized using the solid state boronizing technique. Processes were carried out at the temperatures of 850, 900 and 950 °C for 2, 4 and 6 h of treatment. Abrasive wear behavior of the samples boronized at different temperatures and treatment durations have been examined. Using boronized and unboronized samples, abrasive tests were conducted using pin on disc test apparatus. 80 and 120 mesh aluminum oxide (Al₂O₃) abrasive papers were used in the abrasion experiments and the samples were subjected to abrasion under 10, 20 and 30 N loads. Boronized steels exhibited an improvement in abrasive wear resistance reaching up to 500%. Microstructures and wear surfaces of the samples were inspected using SEM microscopy. SEM examinations revealed that the thickness of the boride layer on the steel surfaces changes with changing process durations and temperatures. The presence of boride formed in the borided layer at the surface of the steels were determined by XRD analysis and microhardness values of the iron borides (FeB, Fe₂B) formed on the steel surface were found to be over 1600 HV.     

Sliding/rolling wear performance of plasma nitrided H11 hot working steel

H11 steel discs were tested by considering sliding/rolling friction under dry and lubricated conditions. The H11 discs were plasma nitrided at 500 °C and 550 °C for 9 h. Wear tests were conducted at different slip ratios of 1.79%, 10.53% and 22.22%. The test loads were 100 N, 150 N and 200 N. It was determined that plasma-nitrided H11 discs had a surface hardness of 1200–1400 HV0.1. Plasma nitriding produced wear performance much higher than those of the un-nitrided but hardened samples. The wear mechanism of the plasma-nitrided discs was a mixture of adhesive wear, abrasive wear and plastic yielding.     

Effect of soft carbon black on tribology of deproteinised and polyisoprene rubbers

In this work, the tribological properties of deproteinised natural rubber (DPNR) were examined and compared with synthetic cis-1,4-polyisoprene rubber (IR), namely Natsyn 2200. The effect of adding carbon black (CB) (0, 25 and 50 phr) to both DPNR and IR on the friction and wear characteristics was investigated. Dry abrasion tests were carried out using pin-on-cylinder tribometer with abrasive paper (Diamond 50) under different operating test conditions such as applied normal load (5–35 N), sliding speed (0.3–1.5 m/s) and sliding distance (90–450 m).Experimental results showed that the addition of CB has significantly affected the wear and friction characteristics of both DPNR and IR, i.e. it reduces the abrasion weight loss by more than 70% compared to unfilled rubber, depending on the test conditions and the concentration of CB. The friction coefficient of DPNR was decreased by about 12.5% upon the addition of 50 phr CB, compared to unfilled DPNR. Meanwhile, adding (25–50 phr) CB to IR drastically deteriorates the friction coefficient, i.e. an increase in the friction by about 200% at 25 phr CB and 300% at 50 phr CB compared to unfilled IR.Finally, scanning electron microscopy (SEM) technique is employed to observe the abrasion pattern of rubber in order to correlate the experimental test results to the wear mechanisms.     

1-N-alkyl -3-methylimidazolium ionic liquids as neat lubricants and lubricant additives in steel–aluminium contacts

The influence of the alkyl chain length and of the anion on the lubricating ability has been studied for the room-temperature ionic liquids (IL) 1-n-alkyl-3-methylimidazolium X⁻ [X = PF₆; n = 6 (L-P106). X = BF₄; n = 2 (L102), 6 (L106), 8 (L108). X = CF₃SO₃; n = 2 (L-T102). X = (4-CH3C6H4SO3); n = 2 (L-To102)]. Neat IL have been used for AISI 52100 steel-ASTM 2011 aluminium contacts in pin-on-disk tests under variable sliding speed. While all IL give initial friction values lower than 0.15, real-time sharp friction increments related to tribochemical processes have been observed for L102 and L-P106, at room-temperature and at 100 °C. Electronic microscopy (SEM), energy dispersive (EDS) and X-ray photoelectron (XPS) spectroscopies show that wear scar surfaces are oxidized to Al₂O₃ and wear debris contain aluminium and iron (for L102) fluorides. For L-P106, the steel surface is covered with a P-containing tribolayer. A change of anion (L-T102; L-To102) reduces friction and wear, but the lowest values are obtained by increasing the alkyl chain length (L106; L108). When the more reactive L102 and L-P106 are used as 1 wt.% base oil additives at 25 °C, tribocorrosion processes are not observed and a friction reduction (69–75% for 1 wt.% L102) and a change from severe (10⁻³ mm³ m⁻¹) to mild wear (10⁻⁴ to 10⁻⁶ mm³ m⁻¹) is obtained with respect to the neat IL. 1 wt.% IL additives also show good lubricating performance at 100 °C.     

Development of a simple ‘temperature versus sliding speed’ wear map for the sliding wear behaviour of dissimilar metallic interfaces

The variation in wear behaviour during limited debris retention sliding wear of Nimonic 80A versus Stellite 6 (counterface) between room temperature and 750 °C, at sliding speeds of 0.314, 0.654 and 0.905 m s⁻¹, was investigated. At 0.314 m s⁻¹, mild oxidational wear was observed at all temperatures, due to transfer and oxidation of Stellite 6-sourced debris to the Nimonic 80A and resultant separation of the Nimonic 80A and Stellite 6 wear surfaces. Between room temperature and 450 °C, this debris mostly remained in the form of loose particles (with only limited compaction), whilst between 510 and 750 °C, the particles were compacted and sintered together to form a wear protective ‘glaze’ layer.At 0.654 and 0.905 m s⁻¹, mild oxidational wear due to transfer and oxidation of Stellite 6-sourced debris was only observed at room temperature and 270 °C (also 390 °C at 0.654 m s⁻¹). At 390 °C (450 °C at 0.654 m s⁻¹) and above, this oxide was completely absent and ‘metal-to-metal’ contact resulted in an intermediate temperature severe wear regime—losses in the form of ejected metallic debris were sourced almost completely from the Nimonic 80A. Oxide debris, this time sourced from the Nimonic 80A sample, did not reappear until 570 °C (630 °C at 0.654 m s⁻¹), however, were insufficient to eliminate completely severe wear until 690 and 750 °C. At both 0.654 and 0.905 m s⁻¹, the oxide now preventing severe wear at 690 and 750 °C tended not to form ‘glaze’ layers on the surface of the Nimonic 80A and instead supported continued high wear by abrasion. This abrasive action was attributed to the poor sintering characteristics of the Nimonic 80A-sourced oxide, in combination with the oxides’ increased mobility and decreased residency.The collected data were used to compose a simple wear map detailing the effects of sliding speed and temperature on the wear of Nimonic 80A slid against Stellite 6, at these speeds and temperatures of between room temperature and 750 °C.     

Effect of three nitriding treatments on tribological performance of 42CrAlMo7 steel in boundary lubrication

Evolution of friction and wear of 42CrAlMo7 steels with different nitriding processes was investigated during boundary-lubricated rolling–sliding tests. The wear behaviour of nitrided steel with a thin compound layer (produced by plasma nitriding and by gas nitriding followed by oxidation) was characterised by the early removal of the compound layer, and the wear resistance was thus, given by the underlying diffusion layer. In the case of the material with a thick compound layer (produced by gas nitriding) wear was restricted to the compound layer. In this material, at low applied load (300 N, i.e. 485 MPa of Hertzian pressure, in this work), after the removal of the external porous layer wear tended to be negligible. At high applied load (1000 N, 890 MPa), on the other hand, the wear rate became higher than that of the diffusion layer. The friction behaviour was followed by determining the λ-factor evolution during each test. For a given λ-factor, the friction coefficients at 300 N were lower than at 1000 N.     

Effect of SiC particles on the friction and wear behavior of Ti3Si(Al)C2-based composites

The non-lubricated, sliding friction and wear behavior of Ti₃Si(Al)C₂ and SiC-reinforced Ti₃Si(Al)C₂ composites against AISI 52100 bearing steel ball were investigated using a ball-on-flat, reciprocating tribometer at room temperature. The contact load was varied from 5 to 20 N. For monolithic Ti₃Si(Al)C₂, high friction coefficients between 0.61 and 0.90 and wear rates between 1.79 × 10⁻³ and 2.68 × 10⁻³ mm³ (N m)⁻¹ were measured. With increasing SiC content in the composites, both the friction coefficients and the wear rates were significantly decreased. The friction coefficients reduced to a value between 0.38 and 0.50, and the wear rates to between 2.64 × 10⁻⁴ and 1.93 × 10⁻⁵ mm³ (N m)⁻¹ when the SiC content ranged from 10 to 30 vol.%. The enhanced wear resistance of Ti₃Si(Al)C₂ is mainly attributed to the facts that the hard SiC particles inhibit the plastic deformation and fracture of the soft matrix, the oxide debris lubricate the counterpair, and the wear mode converts from adhesive wear to abrasive wear during dry sliding.     

Influence of temperature on the fretting response between AISI 301 stainless steel and AISI 52100 steel

Fretting of AISI 301 stainless steel sheet in contact with AISI 52100 steel from 20 °C to 550 °C in air and argon has been studied. Transitions in the mechanical properties of 301SS and oxidative behavior of this pair have been identified as a function of temperature. Strength and ductility of 301SS is reduced from 20 °C to 250 °C, increasing susceptibility to fretting damage. Steady state friction decreases as temperature increases, reducing cyclic stresses. Wear resistance increases in this temperature range, increasing fatigue damage due to the increase in fatigue life associated with increased wear. This study aims to identify the causes of the transitions in behavior and determine the net outcome of the competing effects with regard to fatigue damage.     

Mechanical and tribological properties of NiCr–Al2O3 composites at elevated temperatures

The effect of Al₂O₃ content on the mechanical and tribological properties of Ni–Cr alloy was investigated from room temperature to 1000 °C. The results indicated that NiCr–40 wt% Al₂O₃ composite exhibited good wear resistance and its compressive strength remained 540 MPa even at 1000 °C. The values obtained for flexural strength and fracture toughness at room temperature were 771 MPa, 15.2 MPa m^1/2, respectively. Between 800 °C and 1000 °C, the adhesive and plastic oxide layer on the worn surface of the composite was claimed to be responsible for low friction coefficient and wear rate.     

Tribological properties of Ni-17.5Si-29.3Cr alloy at room and elevated temperatures

The tribological properties of Ni-17.5Si-29.3Cr alloy against Si₃N₄ were studied on a ball-on-disc tribotester between room temperature and 1000 °C. The effects of temperature on the tribological properties of the alloy were investigated. The worn surfaces of the alloy were examined using scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). The results indicated that the tribological behavior of the alloy expressed some differences with increase in testing temperature. At low and moderate temperatures (below 800 °C), the alloy showed excellent wear and oxidation resistances, and the wear rate of the alloy remained in the magnitude of 10^?5 mm³/Nm; but at elevated temperature (800–1000 °C), the wear and oxidation resistances decreased, and the wear rate of the alloy increased up to 10^?4 mm³/Nm. The friction coefficient decreased from 0.58 to 0.46 with the rising of testing temperature from 20 to 600 °C, and then remained nearly constant. The wear mechanism of the alloy was mainly fracture and delamination at low and moderate temperatures, and transformed to adhesive and oxidation at elevated temperatures.     

Tribological characterisation of siliconcarbonitride ceramics derived from preceramic polymers

Amorphous SiCN ceramics were prepared in a laboratory scale as disk shaped specimens with 10 mm diameter and 0.3 mm thickness. The friction and wear behaviour was characterised in gross slip fretting tests under unlubricated conditions at room temperature against steel (100Cr6) and ceramic (Al₂O₃). Tests with a ball-on-disk contact were performed in laboratory air with different content of water vapour. The results show clearly that the relative humidity has a significant effect on friction and wear behaviour. All tests in dry air lead to higher friction and higher wear rate than in normal air. Improved friction and wear behaviour was observed with increasing pyrolysis temperature up to 1100 °C of the SiCN specimens. This is attributed to increasingly better mechanical properties and higher stiffness of the amorphous network due to the evaporation of gaseous organic species and the formation of free graphite like carbon.     

A variable temperature mechanical analysis of ZDDP-derived antiwear films formed on 52100 steel

The nanomechanical properties of antiwear films formed from zinc dialkyl-dithiophosphates (ZDDPs) on steel have been studied by nanoindentation techniques as a function of temperature. X-ray absorption P K- and L- near edge structure (XANES) spectroscopy has shown that films prepared from oils containing ZDDPs on 52100 steel (pin on flat coupons) consist primarily of medium chain polyphosphates with sulphur (S K-edge) predominantly present as sulphide.Using various scanning probe techniques, high-resolution topographic images and mechanical properties can be extracted at the same length scale. Using focused ion beam (FIB) milling we have compared real cross-sectional film thickness with a value estimated from the P K-edge XANES. We report the first measurements of the elastic modulus of the antiwear films at elevated temperatures relevant to the automobile operating conditions (T ≤ 200 °C). The antiwear films demonstrated a relatively constant indentation modulus over a wide range of temperatures consistent with their efficacy in reducing wear by preventing asperity contact.     

A study on erosion of upper bainitic ADI and PDI

Ductile iron containing ∼3.5 wt.% C and 2.1–4.2 wt.% Si (2.1, 2.8 and 4.2 wt.%) was studied. Three sets of specimens with differing Si contents were made into austempered ductile iron (ADI) and pearlite ductile iron (PDI) through heat treatment. These specimens were then eroded with Al₂O₃ particles and SiO₂ particles of 275–295 μm grit size to understand the relationship between erosion rate and microstructure. The ADI specimens were upper bainitic matrices that were austempered for different periods of time at 420 °C. The heat treatment of PDI was conducted at 870 or 930 °C for 1 h then forced air cooled or oil quenched to room temperature.Two types of wear curves, single peak curves and double peak curves, were found when plotting the erosion rate figures derived from the experimental results. 2.1 wt.% Si and 2.8 wt.% Si ADI tempered for a long period of time, due to their decreased retained austenite content and increased carbide content, had a single peak erosion rate curve. This embrittlement effect caused the impact angle of maximum erosion rate to increase from ∼30 to ∼45°. Decreasing the interspacing of the lamellae cementite promoted the hardness and improved the low-angle erosion wear resistance of PDI. The high hardness and brittleness of the matrix reduces the high-angle erosion resistance and the peak erosion rate occurs at a higher angle.For 2.1Si-ADI and 2.8Si-ADI tempered for a short duration, increasing the volume fraction of martensite in the matrix increases the erosion rate at an impact angle of 30°, but the maximum erosion rate is found at 75°. This results in a curve with a double peak. The double peak curve was also observed for high silicon ADI tempered for a long duration. The high solid solution hardness of 4.2Si-ADI, due to low retained austenite content and the presence of carbide in the matrix, results in poor erosion resistance. When this material is austempered for a long period, the erosion rate curve shifts from a single peak curve (30°) to a double peak curve (30°; 60°).     

Wear behavior of electroless Ni–P–B4C composite coatings

In this research, the wear of electroless Ni–P and Ni–P–B₄C composite coatings was reviewed. Auto catalytic reduction of Ni in nickel sulfate and sodium hypophosphate bath including suspended B₄C particles with different concentration was used to create composite coatings with 12, 18, 25 and 33 vol.% of B₄C particles. Coatings 35 μm thick were heat treated at 400 °C for one hour in an argon atmosphere and the wear resistance and friction coefficient of heat-treated samples were determined by block-on-ring tests. All wear tests were carried out at 24 °C, 35% moisture, 0.164 m/s sliding speed and about 1000 m sliding distance. Graphs show that an electroless Ni–P–B₄C composite coating with 25 vol.% of B₄C had the best wear resistance against a CK45 steel counterface.     

Tribological behaviors of Ti–6Al–4V modified by chemical methods

In order to improve the tribological properties of titanium-based implants, sodium hydroxide (NaOH), hydrogen peroxide (H₂O₂) solutions, sol–gel hydroxyapatite (HA) film, thermal treatment and combined methods of NaOH solution/HA film, H₂O₂ solution/HA film are used to modify the surfaces of Ti–6Al–4V (coded TC4). The chemical states of some typical elements in the modified surfaces were detected by means of X-ray photoelectron spectroscopy (XPS). The tribological properties of modified surfaces sliding against an AISI52100 steel ball were evaluated on a reciprocating friction and wear tester. As the results, complex surfaces with varied components are obtained. All the methods are effective in improving the wear resistance of Ti–6Al–4V in different degrees. Among all, the surface modified by the combined method of NaOH solution/HA film gives the best tribological performances. The friction coefficient is also greatly reduced by the modification of NaOH solution. The order of the wear resistance under 3 N is as following: Ti–NaOH–HA>Ti–NaOH>Ti–HA>Ti–H₂O₂–HA>Ti–H₂O₂ >Ti–500; under 1 N is Ti–HA, Ti–NaOH–HA>Ti–NaOH. For Ti–H₂O₂, a very low friction coefficient and long wear life over 2000 passes is obtained under 1 N. SEM observation of the morphologies of worn surfaces indicates that the wear of TC4 is characteristic of abrasive wear. Differently, abrasion, plastic deformation and micro–crack dominate the wear of Ti–HA; slight abrasive wear dominate the wear mechanism of Ti–NaOH and microfracture and abrasive wear for Ti–NaOH–HA and Ti–H₂O₂–HA, while the sample modified by thermal treatment is characterized by sever fracture. The superior friction reduction and wear resistance of HA films are greatly attributed to the slight plastic deformation of the film. NaOH solution is superior in improving the wear resistance and decreasing the friction coefficient under relative higher load (3 N) and H₂O₂ is helpful to reduce friction and wear under relatively lower load (1 N). Combined method of Ti–NaOH–HA is suggested to improve the wear resistance of Ti–6Al–4V for medial applications under fretting situations.     

Comparison of abrasive wear behavior of ductile iron with different dual matrix structures

Abrasive wear behavior of ductile irons with different dual matrix structures has been investigated. In order to obtain ductile irons with different dual matrix structures an unalloyed ductile iron specimens were austenitized in the two-phase region (α + γ) at various temperature (795 °C and 815 °C) and then rapidly transferred to a salt bath held at the 365 °C for austempering for 30, 90 and 120 min. Some specimens were quenched from same intercritical austenitizing temperatures and tempered at 550 °C for 60 and 300 min. Some specimens were also conventionally austempered and/or quenched from 900 °C for comparison. Experimental results showed that, the tensile strength increased and ductility decreased with increasing martensite volume fraction in the specimen with martensite dual matrix structure. By increasing the tempering time, the yield and UTS decreased and ductility increased. In addition, the specimens with ausferrite dual matrix structures exhibited much greater ductility than conventionally austempered ones. The tensile strength increased while ductility decreased with increasing ausferrite volume fraction. Furthermore in all austenitized specimens, the abrasive weight loss of austempered specimens (A series) was lower than those of quenched specimens (Q series) irrespective of all loads due to increased AFVFs and total elongation. It was shown that wear loss of both tested materials in abrasive wear was proportional to the applied load. However, there was a decreasing trend in the weight loss of the A795 with dual matrix structure austempered for 30 and 90 min with increasing load. The reason was because of the fact that the specimen surface was work hardened with cutting efficiency of the abrasive reduced through clogging, and attrition jointly leading to less weight loss. Moreover, increasing the austempering time caused more ductile ausferritic structure to displace hard martensite. In all austempered samples, the abrasive weight loss increased with increasing the austempering time. As for the case of Q samples, the abrasive weight loss increased more or less linearly with load since an increase in the applied load might increase the contact stress. Among the Q samples, the highest weight loss was obtained for the Q795-300, Q815-300 sample because of lower martensite volume fraction, but the lowest weight loss was observed for the Q900 sample due to the highest martensite volume fraction. For Q900 samples, the amount of fracture of the abrasives was found to be increase with the harder specimen, and it may have contributed somewhat to the increased wear.Furthermore, microchips were dominant wear mechanism by cutting mode for higher ductile materials while micro-ploughing was predominant wear for harder materials, but wear also occurred by combinations of ploughing and embedding particles into the surface for Q samples. Cross-section examination by SEM through the wear surfaces revealed that a more smoother surface was observed for the A795 sample than that of the Q795 sample. However, a more rougher surface was observed for the A900-120 sample than that of the Q900 sample.     

A comparison of boundary wear film formation on steel and a thermal sprayed Co/Cr/Mo coating under sliding conditions

In this paper, the action of the zinc dialkyl dithiophosphate (ZDDP) anti-wear additive has been examined on two different materials (Steel AISI 52100 and a Co/Cr/Mo thermal spray coating) sliding against cast iron in reciprocating mode. Tests have been conducted under lubricated wear conditions at relatively low (20, 50 °C) and elevated (up to 100 °C) bulk oil temperatures. A comparison is made between the friction, wear and chemical nature of the wear film formed under varying temperatures, on two materials, in two lubricants (one free from and one containing ZDDP) and after different test durations. The wear film has been examined by energy dispersive X-ray analysis (EDAX) and X-ray photoelectron spectroscopy (XPS).In this work, it has been shown in this work that the friction coefficient is dependent on the temperature, the lubricant and the nature of the contacting surfaces. In the presence of ZDDP, a wear film, comprising Zn, S and P, forms even at the lowest bulk oil temperature of 20 °C. The nature of the film is dependent on the substrate material and the steel and Co/Cr/Mo coating showed contrasting film characteristics. In this paper, the wear and friction results for each couple in oil containing and free from additives is discussed with reference to the nature of the wear film. A correlation has been made between the wear, friction and chemical analysis measurements.