Wear Mode Transition Research Articles

High temperature wear behavior of Al–4Cu–TiB 2in situ composites

The effect of sliding temperature and load on the wear behavior of Al–4Cu alloy and Al–4Cu–TiB 2 in situ composites was studied in this paper. The wear resistance of the Al–4Cu alloy increased with increase in wt.% of reinforcement TiB 2 particles at all temperatures and loads. The transition in the wear mode from mild to severe wear was strongly influenced by the addition of TiB 2 particles. The Al–4Cu alloy showed a transition from mild to severe wear at a load of 80 N and at a sliding temperature of 100 °C. But with the addition of 5 and 10 wt.% of in situ TiB 2 particles to the Al–4Cu matrix, the transition temperatures are increased to 200 and 300 °C and the loads are increased to 100 and 120 N, respectively. Analysis of wear surfaces by scanning electron microscopy revealed the transition in wear mode. It was observed that at elevated temperature the predominant wear mechanisms for the Al–4Cu alloys are adhesion and metal flow, whereas for Al–4Cu–TiB 2 composites oxidation, delamination and metal flow are the most dominant wear mechanisms.

Relationship between test severity and wear mode transition in micro-abrasive wear tests

Recently, the micro-scale abrasive wear test has gained large acceptance in universities and research centers, being widely used in studies on the abrasive wear of materials. The purpose of this work is to relate a quantity called test severity ( S test) with the abrasive wear mode transition. The analysis took into consideration the hardness of the materials; the contact pressure ( P) between the specimen and the ball and the equipment configuration (fixed-ball or free-ball). Tests were conducted with balls of AISI 52100 steel and specimens of ISO P20 cemented carbide (WC-Co) and AISI M2 tool steel. The abrasive slurry was prepared with black silicon carbide (SiC) particles (average particle size of 5 μm) and distilled water. The results were analyzed in plots of S test and A g/ A p as a function of test time ( t) and V as a function of P, where A g is the projected area fraction with grooving abrasion; A p the total projected area and V is the volume of the worn crater. The results allowed observing that the value of S test decreased from the beginning to the end of all tests. When the results obtained with fixed-ball and free-ball equipment were compared, this decrease in S test was similar in the case of the WC-Co specimen, for which the hardness of the specimen ( H s) was larger than the hardness of the ball ( H b). The decrease in S test was different in the case of the AISI M2 specimen, for which H s < H b. Tests were also associated with a decrease in the ratio A g/ A p as a function of test time. A transition from mixed mode into pure rolling abrasion occurred at similar test times in the cases with similar severity evolution and, for the AISI M2 specimen, occurred earlier for the condition with lower test severity.

Study on Wear Mode of Silicon Nitride Balls in Lapping Process

To understand the mechanism involved in the lapping process of the silicon nitride balls, the wear mode is investigated in this paper. The abrasion tests were performed on a ball-plate wear test apparatus with different loads (0~2N/ball) and slurry concentrations (5%wt~30%wt W20 B4C3). The abraded surface is observed by optical telescope. A wear-mode map, which defines the regimes for two-body abrasion or three-body abrasion dominating in the micro-scale abrasion test, is plotted with two axes: load and concentration of abrasive. An empirical formula for the wear mode transition is adopted to calculate the transition point S*, which can then used to predict the wear mode in lapping process of silicon nitride ball.

Role of wear particles in severe–mild wear transition

Severe–mild wear transition is one of the most interesting phenomena in adhesive wear, because the wear rate decreases drastically after the transition. This paper is aimed at clarifying the mechanism of wear mode transition from severe to mild. A copper pin was rubbed against rotating iron disk in laboratory air. Sliding conditions such as load and sliding velocity were changed. To focus on the role of wear particles, they were removed by air cleaner. To control the behavior of wear particles, the set position of pin-on-disk tester was changed. The inner structures of severe and mild wear particles were also examined. As the wear mode changed from severe to mild, morphologies of wear particles also changed and resulted in smaller particle sizes. However it is to be noted that some mild wear particles were noticeable even in severe wear mode and that some severe wear particles were also found at the early stage of mild wear mode. Large black wear particles produced in mild wear mode were composed of severe wear particles in the core, which was covered by fine black mild wear particles. When small wear particles are formed they are easily oxidized and transform to mild wear particles. However if they were removed from the surface, mild wear was not observed. The attachment of mild wear particles to the worn surface formed a protective oxide film, and induced mild wear. As the sliding velocity increased, the sliding distance needed for severe–mild wear transition increased proportionally at relatively low load conditions. It indicates the existence of characteristic time for the transition. It is the necessary time for the production of adequate amount of mild wear particles and their attachment on the surface.

High Pressure Wear Characteristics of Alloyed Ductile Cast Iron - Effect of Cu, Mn, Si and Mo

Under a high-pressure condition, the wear characteristics of alloyed and unalloyed ductile cast iron were investigated. Mn, Cu, Si and Mo were chosen as alloying elements, and their effects on mechanical properties of hardness and toughness were correlated with wear properties. In most cases, high-pressure wear of alloyed and unalloyed DCI were sequentially developed by mild wear region followed by severe wear. The transition of wear mode was indicated by the drastic increase of friction coefficient and wear rate. The observation of worn surface at mild-wear region suggested that wear had been concentrated at graphite phases, whereas severe wear mode damaged both of graphite and matrix. It was found that DCI alloyed with Si-Mo exhibited the most prominent resistance to the beginning of severe wear while the toughness of DCI was also a crucial factor.

The effects of an electric current on the sliding wear of cast iron

Dry sliding wear tests were carried out to clarify the influence of an electric current on friction and wear of cast iron. Some carbon steels were also examined for comparison. A ball-on-plate type tribotester was used with a high-carbon chromium bearing steel as a fixed ball. It was found that changes in the friction coefficient, due to an increase in electric current, were completely different for cast irons than for carbon steels. The friction coefficient of cast iron is lower than that of carbon steel under zero current conditions, but with an increase in applied current the coefficient increases. In contrast, the friction of steels decreases under a high electric current. A further increase in current produced an inversion of the friction coefficient between cast irons and steels. The direction of the current affects the amount of wear: the anode of the couple always experiences heavier wear than the cathode, in the case of both cast irons and carbon steels. The wear of cast iron increased with an increase in electric current under all tested contact loads. However, the wear of the carbon steel showed little increase (with increasing electric current) under high contact load. These differences in the tribological behavior under electric current of both cast iron and carbon steel are attributed to the difference in melting point of the materials, which changes the transition of wear mode from adhesion to fusion.

Dry and lubricated wear resistance of mechanically-alloyed aluminium-base sintered composites

The friction and wear behaviour of three mechanically alloyed aluminium-base materials, consolidated by an alternative powder-metallurgy process, has been studied with a pin-on-disk tribometer, sliding against AISI 52100 steel pins. Their tribological properties have been compared, using simple sintered aluminium, as standard material. Volume loss, under dry wear conditions, is very dependent on the measurement method. The more regular wear tracks, achieved under lubrication, allows the track-width method to be used with better accuracy. In general, unreinforced Al shows the lowest wear resistance, while composites with the highest hardness and second-phase volume content are the most wear resistant, especially at high load. Unreinforced Al suffers a transition in wear mode, from mild to severe wear, at load 4.90 N, in lubricated tests. The wear mechanism is of the adhesive/abrasive type.

The influence of ball size on tribological behaviour of MoS 2 coating tested on a ball-on-disk wear rig

The effect of ball diameter on wear and friction of a molybdenum disulphide (MoS 2) coating deposited using the closed-field magnetron sputtering technique has been investigated on a ball-on-disk wear rig sliding against uncoated steel ball-bearing balls. It was observed that the wear rate of the coating decreased significantly with increase in ball diameter. Correspondingly, the average friction coefficient in the steady state of sliding increased with increase in ball diameter. Under the present experimental conditions, the effect of ball size on wear and friction of the coating vanished when the diameter of the ball exceeded 6.35 mm. This phenomenon is thought to be a result of wear mode transition as a function of contact pressure at the apparent area of contact from a low-rate ‘mild’ wear regime to a high-rate ‘severe’ wear regime when the contact pressure exceeds some critical value. Simulation results using a previously presented model based on the above assumption showed a good agreement with the experimental observations.

Effect of arc discharge on the wear rate and wear mode transition of a copper-impregnated metallized carbon contact strip sliding against a copper disk

Wear of the contact strip on the pantograph of electric railway vehicles is governed mainly by arc discharge occurring simultaneously with break of contact between the strip and trolley wire. As a step to clarify the wear mechanism of metallized carbon contact strips under the occurrence of contact break arc discharge, a detailed sliding wear test of 30 min duration was carried out for the combination of a copper-impregnated carbon strip and a copper disk at a sliding speed of 100 km/h. The worn surfaces of the strip and disk were observed every 5 min. The voltage drop and electric current were measured throughout the test, and the occurrence and energy of the arc discharge were evaluated for each revolution of the disk. The wear process is considered in terms of the wear mode transition, and the effect of arc discharge on the mode transition and wear rate of the strip is discussed.

Microscopic wear mechanisms of Ti ion-implanted 1C-3Cr steel

In order to clarify the microscopic wear mechanism of Ti ion-implanted 1C-Cr steel, wear process was observed in-situ during sliding in a SEM Tribosystem. Three wear modes were observed for Ti-implanted specimen as ploughing, shear-tongue (Type I) and shear-tongue (Type II). On the other hand, only two wear modes were observed for unimplanted specimen as ploughing and shear-tongue (Type II). Wear modes varied from ploughing through shear-tongue (Type I) and to shear-tongue (Type II) for ion implanted specimen with the increasing of friction cycles. Transition friction cycles of wear mode decreased with the increase of load. The depth of the wear groove for the transition of wear mode from shear-tongue (Type I) to shear-tongue (Type II) corresponded to the depth profile of the concentration of Ti ion. The depth of wear groove for Ti ion-implanted specimen is about half of that of unimplanted specimen.

The transition of wear mode during the running-in process of silicon nitride sliding in water

When silicon nitride slides against itself in water, an extremely low friction coefficient can be obtained by having a suitable running-in condition. This paper focuses of the dynamic running-in process of silicon nitride sliding in water under the conditions of load at 1–3 N, sliding velocity at 30–120 mm s −1 and temperature at 20–80°C with a pin-on-disc apparatus. The results show that the following. (I) Wear mechanisms change from mechanically dominated wear to tribochemically dominated wear as the sliding distance increases during the running-in process. This is mainly because of the reduction of contact pressure and smoothing of the friction surface. (2) Wear particles change from transgranular fracture-induced wear particles, intergranular fracture-induced wear particles and film delamination-induced wear particles, to net-like agglomerates of wear particles as sliding distance increases during the running-in process. (3) Net-like agglomerates of wear particles came mainly from powdering, oxidation and hydration of large transgranular and intergranular-induced wear particles. (4) Water lubrication of silicon nitride with a pin-on-disc configuration is partially hydrodynamic lubrication due to the ultra-smooth surface and partially boundary lubrication due to the colloidal silica layer.

Wear mode transition of hard films on Al alloys under variable normal load

The purpose of this investigation was to analyse the microscopic wear mode transition of TiN, Cr, and anodic oxide films on Al alloys in reciprocating sliding under lubricated conditions. For this purpose, a CCD microscope tribosystem was developed. By using this system, the dynamic wear processes of hard films could be observed successively; the following results were obtained. There are two critical normal loads Wc1 and WC2, where Wc1 is the critical normal load below which there is no spalling of the coating film at any number of reciprocations and Wc2 is the critical normal load for spalling or flake formation of the coating film after a single sliding passage. The TiN film showed higher wear resistance when W < Wc1. When W < Wc1, spalling of the coating film did not occur at any time during the sliding test. When Wc1 ≥ W < WC2, spalling of the coating film occurred after a certain number of reciprocations. When W ≥ Wc2, spalling or flake formation of the coating film occurred after a single passage. The specific wear rate also changed dramatically with the transition of the wear mode.

Reciprocal sliding wear of SiC particle-reinforced AlCu aluminium matrix composites against stainless steel, high speed tool steel and ceramics II. Wear mechanisms

The friction and wear of AlCuSiC aluminium matrix composite pins dry sliding against 4Cr 13, W 18Cr 4V and Si 3N 4(SN) ceramic blocks were investigated in a reciprocal friction test machine under applied loads of 20–175 N and reciprocal speeds of 0.075–1.2 ms −1. The wom surface morphology was analysed to clarify the wear mechanisms. Wear mechanism maps were constructed to elucidate the effects of test condition such as applied load, reciprocal speed and counterface materials on the wear mode and wear mechanism transition. Wear models were proposed to explain the experimental phenomena based on the characterization studies.

Transitions of microscopic wear mode of silicon carbide coatings by chemical vapor deposition during repeated sliding observed in a scanning electron microscope tribosystem

The purpose of this investigation is to analyze microscopic wear mechanisms of silicon carbide coatings by chemical vapor deposition (CVD). For this purpose, the wear processes during one hundred sliding cycles were observed successively in a scanning electron microscope (SEM) tribosystem. The results were compared with those of uncoated silicon carbide. The following results were obtained. (1) Wear modes are classified into four, they are ploughing, powder formation, crack formation and flake formation. These wear modes except for ploughing are mainly caused by surface crack propagation. (2) Silicon carbide coatings showed higher wear resistance than uncoated silicon carbide, because there are less initial surface cracks in the silicon carbide coatings. (3) The condition for wear mode transition can be explained theoretically by using the parameters of severity of contact, S c , S c , S* c , and the friction coefficient μ, where S c=P max(R max) 1/2/K 1c and S c * =H v(R max) 1/2/K 1c .

Transitions of microscopic wear mechanism for Cr 2O 3 ceramic coatings during repeated sliding observed in a scanning électron microscope tribosystem

The purpose of this investigation is to analyse microscopic wear modes and their transitions for Cr 2O 3 coatings in repeated sliding. For this purpose the wear processes during 100 sliding cycles were observed successively in a scanning electron microscope tribosystem. They were also compared with those of a metal, SUS304 stainless steel. The type of wear test was pin on disc. Cr 2O 3 coatings on SUS304 stainless steel were used for the disc specimens. The thickness of the coatings was 400 μm. The pin specimen was made of single-crystal diamond with a hemispherical tip of radius 30 μm. The sliding velocity was 400 μm s −1. The normal load was changed from 0.07 to 1.5 N. The following results were obtained. 1. (1) The wear modes are classified into crack and powder formation, flake formation and ploughing and powder formation. These wear modes are mainly caused by surface crack propagation. 2. (2) The wear modes change during repeated sliding as follows for loads from 0.2 to 1.5 N: crack and powder formation (low wear rate)→flake formation (high wear rate)→ploughing and powder formation (negligible wear rate). When W=0.07 N, the wear mode is ploughing and powder formation and there is no transition to other wear modes. 3. (3) The condition for wear mode transition can be explained theoretically by using the parameter of severity of contact, S c , and the friction coefficient μ, where S c = P max ( R max) 1 2 /K Ic .

The study of microscopic wear mechanism by a SEM-tribosystem. Transition of microscopic wear mode during repeated sliding friction.

Microscopic wear mechanism during repeated sliding was investigated by in-situ observation with a newly developed SEM-tribosystem. Microscopic wear mode transition during repeated sliding progressed from cutting to wedge to shear-tongue and to ploughing. The transition between wear modes coincided with the change in the degree of penetration, Dpn, which was introduced as an index to describe the severity of microscopic contact. In addition, the relationship between the number of sliding cycles, N, and the wear coefficient, K, was explained by using the degree of penetration, Dpn.

The transitions between microscopic wear modes during repeated sliding friction observed by a scanning electron microscope tribosystem

In order to analyse the microscopic wear mechanism in repeat-pass sliding, the wear process was observed successively over ten cycles of sliding in a newly developed scanning electron microscope tribosystem. The wear process was recorded with a video tape recorder. The type of wear test was pin-on-disk. The pin specimen was made of tungsten carbide. The hemispherical pin tip radius was 30 μm. The disk specimen was made of SUS 304 stainless steel. The sliding velocity was 40 μm s −1. The normal load could be varied from 0.07 to 1.5 N. The following principal results were obtained. 1. (1) Wear mode transition during repeated sliding progresses from cutting, to wedge forming, to shear-tongue forming and then to ploughing. 2. (2) The critical conditions for the transitions between wear modes are expressed as follows: 0.27 < D p cutting; 0.09 < D p < 0.27 wedge forming; 0.06 < D p < 0.09 shear-tongue forming; D p < 0.06 ploughing; where D p is the ratio of the depth of penetration to the length of contact parallel to the sliding direction. It is expressed as a function of normal load, disk specimen hardness, pin specimen radius and number of friction cycles. 3. (3) The conditions for wear mode transition can be explained theoretically by using a wear mode diagram.

Severe-mild wear transition in AlZn rubbing caused by the formation of semiconducting materials on the sliding surface

A severe-mild wear transition was found in Alrubbing. Aluminium and zinc are both non-transition metals, hence mild wear has never been observed in AlAl and ZnZn rubbings under dry sliding conditions in air. However, mild wear was found during aluminium pin and zinc disk rubbing. From the measurement of current-voltage characteristics on the zinc disk surface, it was determined that the transition of wear mode from severe to mild wear occurred due to the formation of a semiconducting material in the wear track during sliding. The occurrence of mild wear in AlZn rubbing is discussed in reference to the formation of semiconducting material on the sliding surface. Further, the occurrence of mild wear in AlZn rubbing through the formation of semiconducting materials was endorsed by the wear of semiconductor silicon in sliding contact with metals.

Exo-electron emission as a method of investigating plastically deformed metal surfaces : V. S. Kortov and R. L. Minto, Soviet Mater. Sci. 2 (3) (1966) 197–201; 5 figs., 33; refs. (Translation by Faraday Press, New York, of Fis.-Khim. Mekhan. Mater., 2 (3) (1966) 272–278.)

This paper offers a simplified model of seizure process that provides a foundation to develop the effective friction control in tribo-systems in one of a great National R&D program to prevent global warming that has been presented by Japanese Ministry of Economy, Trade and Industry and is supported financially by New Energy and Industrial Technology Development Organization.The seizure is defined as severe wear mode in this paper and thus the critical condition of seizure is that of the transition from mild to severe wear mode. In the severe wear mode, plastic deformation called ‘wedge’ by Cocks or ‘prow’ by Antler is considered to take place in considerably large area due to the combination of contact pressure and shear stress. The concept, with which Burwell and Strang accounted the effect of load on the transition of wear mode, is employed for the critical pressure. The hardness distribution, which relates the critical pressure, is assumed in a simple function estimated roughly from the temperature distribution in the direction of depth from surface.The relation between seizure and the product of contact pressure and sliding velocity, i.e., pV value, is discussed.