EN24 Steel Disc Research Articles

A study of microstructure and wear behaviour of TiB2/Al metal matrix composites

The present paper deals with the study of microstructure and wear characteristics of TiB2 reinforced aluminium metal matrix composites (MMCs). Matrix alloys with 5, 10 and 15% of TiB2 were made using stir casting technique. Effect of sliding velocity on the wear behaviour and tribo-chemistry of the worn surfaces of both matrix and composites sliding against a EN24 steel disc has been investigated under dry conditions. A pin-on-disc wear testing machine was used to find the wear rate, in which EN24 steel disc was used as the counter face, loads of 10-60N in steps of 10N and speeds of 100, 200, 300, 400 and 500 rpm were employed. The results showed that the wear rate was increased with an increase in load and sliding speed for both the materials. However, a lower wear rate was obtained for MMCs when compared to the matrix alloys. The wear transition from slight to severe was presented at the critical applied loads. The transition loads for the MMCs were much higher than that of the matrix alloy. The transition loads were increased with increase in TiB2 and the same was decreased with the increase of sliding speeds. The SEM and EDS analyses were undertaken to demonstrate the effect of TiB2 particles on the wear mechanism for each conditions.

Influence of process and test parameters on the dry sliding wear behaviour of Al-Pb alloys produced by mechanical alloying

In the work presented here, the aluminium alloys with lead ranging from 5 to 25 wt% are produced by mechanical alloying (MA) of Al-Pb powders in argon atmosphere. The authors studied the effect of alloy composition and ball to charge ratio on densification as well as wear behaviour of Al-Pb alloys processed through ball milling and attrition milling routes. Powder X-ray diffractometer, scanning electron microscope, optical microscope and hardness and tensile test data are used to characterise the microstructure and mechanical properties of Al-Pb alloys. The influence of lead content, load and sliding speed on wear characteristics of the alloys is examined in dry sliding against EN-24 steel disc, using a pin-on-disc type of tribometer. Further, the tribological behaviour of the alloys is compared to determine an effective way of improving the microstructure, mechanical and tribological properties of Al-Pb alloys. The study reveals that higher ball to charge ratios will be beneficial from the point of view of densification and MA through attrition milling results in better tribological performance of Al-Pb alloys compared to ball milled alloys.

Friction and sliding wear of UHMWPE modified cotton fibre reinforced polyester composites

Ultrahigh molecular weight polyethylene (UHMWPE) modified polyester-cotton composites were developed and studied for friction and sliding wear behaviour at different applied loads and UHMWPE concentrations. Sliding wear tests were conducted by using pin-on-disc apparatus. Composites in the form of the pin were tested against EN-24 steel disc. The specific wear rate of polyester reduced on reinforcement of cotton and on addition of UHMWPE. The coefficient of friction of polyester resin increased on cotton reinforcement and reduced significantly on addition of UHMWPE in cotton polyester composite. The composites exhibited reductions in specific wear rate against the normal load in the specimens those containing 7.41 or higher volume percent of UHMWPE. The significant reduction in wear rate of UHMWPE modified polyester-cotton composite has been discussed with the help of SEM observations of worn surfaces and coefficient of friction. The addition of 14.19 vol.% UHMWPE in polyester resin brought down the value of μ to nearly half to that of polyester resin and 1/3rd of cotton polyester composite.

Performance of monolithic and TiB 2 reinforced MoSi 2 in dry sliding contact with steel

MoSi 2 and its composite with TiB 2 (10 and 20 wt.%) particulates were synthesized by the hot pressing technique. Dry sliding wear experiments were done on these samples by pin-on-disc method on an EN-24 steel disc. It was observed that the densification and the reinforcement of the matrix are beneficial in reducing the friction and wear of MoSi 2. The tribofilm that was formed during sliding contained both the disc and the pin material.

Wear characteristics of phosphor–bronze/silicon carbide particulate composites

The tribological properties of metal matrix composites (MMCs) is of interest in several applications like bearing sleeves, piston and cylinder liners, aircraft brakes, etc. The wear behavior of unreinforced as well as SiC particles reinforced phosphor–bronze alloy composite materials is studied as a function of sliding speed and applied loads under unlubricated conditions. The content of SiC particles in the composites was varied from 1 to 5% in steps of 2% by weight. A pin-on-disc wear testing machine was used to evaluate the wear rate, in which EN24 steel disc was used as the counterface. Loads of 20–160 N in steps of 20 N and speeds of 1.25, 1.56 and 1.87 m/s was employed. The results indicated that the wear rate of both the composites and the matrix alloy increased with increase in load and sliding speed. However, the composites exhibited lower wear rate than the alloys. It was found that above a critical applied load, there exists a transition from mild to severe wear both in the unreinforced alloy and in the composites. But the transition loads for the composites were much higher than that of the unreinforced alloy. The transition loads increased with the increase in weight percent of SiC particles, but decrease with the increase in sliding speeds.

Dry sliding wear of garnet reinforced zinc/aluminium metal matrix composites

The unlubricated sliding wear behavior of ZA-27 alloy composites reinforced with garnet particles of size 30–50 μm was evaluated. The content of garnet in the alloy was varied from 2 to 6% in steps of 2 wt.%. Liquid metallurgy technique was used to fabricate the composites. A pin-on-disc wear-testing machine was used to evaluate the wear rate, in which an EN24 steel disc was used as the counterface. Results indicated that the wear rates of the composites were lower than that of the matrix alloy and further decreased with the increase in garnet content. However, in both unreinforced alloy and reinforced composites, the wear rates increased with the increase in load and the sliding speed. Increase in the applied load increased the wear severity by changing the wear mechanism from abrasion to particle cracking induced delamination wear. It was found that with the increase in garnet content, the wear resistance increased monotonically. The observations have been explained using scanning electron microscopy (SEM) analysis of the worn surfaces and the subsurface of the composites. The debris size is of the order of millimeters at higher load while at the lower load, it is of the order of a few hundred micrometers. On the basis of the above experimental observation, the sequence of micromechnical events, which lead to the generation of wear debris, has been surmized.

Sliding wear of PP/UHMWPE blends: effect of blend composition

In the present investigation, a wear resistant polymer, ultra high molecular weight polyethylene (UHMWPE) was melt blended with isotactic polypropylene (PP) in different proportions. Sliding wear tests were conducted by using Cameron Plint pin-on-disc apparatus. Polymer samples in the form of the pin were tested against EN-24 steel disc at different pressures and sliding speeds. The wear volume of PP reduces significantly on the addition of UHMWPE. At 0.28 m/s sliding speed, wear rate of PP was 15×10 −12 m 3/m which reduces to 0.28×10 −12 m 3/m on addition of 15 wt.% of UHMWPE. At 1.09 m/s sliding speed, PP deforms, while 15 wt.% of UHMWPE sample does not show significant deformation. Wear loss of 15 wt.% UHMWPE filled PP blend significantly low as compared to PP. Reduction in wear loss of UHMWPE filled PP blend has been attributed to the reduction in temperature of contact surface. Worn surface of the test sample showed two distinct morphological regions.

Evaluation of sliding wear behaviour of feldspar particle-reinforced magnesium alloy composites

The unlubricated sliding wear behavior of magnesium alloy AZ91 composites reinforced with feldspar particles of size 30–50 μm was evaluated. The content of feldspar in the alloy was varied from 1% to 5% in steps of 2-wt.%. Liquid metallurgy technique was used to fabricate the composites. A pin-on-disc wear-testing machine was used to evaluate the wear rate, in which an EN24 steel disc was used as the counterface. Results indicated that the wear rates of the composites were lower than that of the matrix alloy and further decreased with the increase in feldspar content. However, in both unreinforced alloy and reinforced composites, the wear rates increased with the increase in load and the sliding speed. Increase in the applied load increased the wear severity by changing the wear mechanism from abrasion to particle cracking induced delamination wear. It was found that with the increase in feldspar content, the wear resistance increased monotonically. The observations have been explained using scanning electron microscopy (SEM) analysis of the worn surfaces and the subsurface of the composites.

Sliding wear behaviour of zircon particles reinforced ZA-27 alloy composite materials

The present paper is a report of an investigation made to study the unlubricated sliding wear behaviour of zinc–aluminium (ZA) alloy composites reinforced with zircon particles of size 30–50 μm. The content of zircon in the alloy was varied from 1–5% in steps of 2 wt.%. The liquid metallurgy technique was used to fabricate the composites. A pin-on-disc wear testing machine was used to evaluate the wear rate, in which a hardened EN24 steel disc was used as the counterface. The results indicated that the wear rate of the composites was lesser than that of the matrix alloy and it further decreased with the increase in zircon content. However, the material loss in terms of wear rate and the wear volume increased with the increase in load and sliding distance, respectively, both in the case of composites and the alloy. Increase in the applied load increased the wear severity by changing the wear mechanism from abrasion to particle cracking induced delamination wear. It was found that with the increase in zircon content, the wear resistance increased monotonically. The observations have been explained using scanning electron micrography (SEM) analysis of the worn surfaces and the subsurface of the composites as well as the base alloy.

Sliding wear response of a zinc-based alloy compared to a copper-based alloy

In the present investigation, an attempt has been made to study the wear response of a zinc-based alloy at different sliding speeds and pressures. The wear behavior of the zinc-based alloy has been compared to that of a conventionally used copper-based alloy against an EN24 steel disc. Operative wear mechanisms have also been discussed through the examination of wear surfaces, subsurface regions, and debris particles.

Observations on the role of the steel disc counterface during the sliding of various structural ceramics

Sliding wear characteristics and mechanisms of structural ceramics, namely A1 20 3, zirconia-toughened alumina, tetragonal zirconia polycrystals (TZP) and Si 3N 4 against a steel counterface are influenced by mechanical and tribochemical interactions, specific to the combinations studied. The present paper studies the role of the disc in the sliding wear process of the above ceramics. Experiments were conducted at a pressure of 15.5 MPa between 0.1 and 12.0 m s −1 with ceramic pins sliding against an EN-24 steel disc. Except in the case of TZP, the disc morphology is sensitive to variations in speed rather than to the pin material. The disc track is (i) mildly abraded at low speeds (about 0.1–0.75 m s −1), (ii) severely abraded at intermediate speeds (about 1.0–3.0 m s −1), (iii) covered with black patches at high speeds (about 4.0–6.0 m s −1) and (iv) completely black at very high speeds (about 7.0–12.0 m s −1). In the case of TZP, although black patches appear, transfer of TZP onto the disc surface and high wear of TZP occurs at 4.0 m s −1. The order of the wear of the disc estimated from profilometric measurements is the same for all the ceramics. Except for Si 3N 4, the onset of wear of the ceramics is associated with the appearance of deep ‘V’ grooves on either side of the profile of the disc track. This can be explained on the basis of the thermal and hardness variations. Although other interaction products specific to the ceramic pin are present, the formation of iron oxides dominates the wear of the disc.

High speed sliding of Al 2O 3 pins against an En-24 steel disc

During the high speed sliding of an 87% Al 2O 3 pin against steel, surface chemical interactions lead to the formation of a surface layer. The coefficient of friction is affected by the surface layer and under certain conditions starts to oscillate between two levels, while under other conditions it has a steady single value. The factors which decide the nature of the friction appear to be not only the speed and pressure, but also the relative contact area (the ratio of the pin surface area to the disc track area). The following empirical relation has been suggested to identify the occurrence of oscillating friction: N = S 2 P 0.75 A 0.5 where S is the speed (m s −1), P the pressure (MPa) and A the ratio of the contact area of the pin to the disc track area. For N < 19 the expected behaviour is that of R3, for 19 < N < 21 the response can be of either regions and for N > 21 R4 behaviour occurs.