Tangential Wear Research Articles

Effect of strength and toughness of ceramic particles on impact abrasive wear resistance of iron matrix composites

The wear resistance of ceramic particle reinforced metal matrix composites is closely related to the properties of ceramic particles. In this study, three kinds of ceramic particle (with 30 % volume fraction) reinforced iron matrix composites (Al2O3/Fe45, ZTA(Zirconia toughened alumina ceramic particles)/Fe45 and ZrO2/Fe45) were prepared by powder metallurgy method. The mechanical properties, impact abrasive wear resistance and impact abrasive wear mechanism of the composites were studied, and the phase transformation of ceramic particles in the composites was analyzed. The results show that the elastic modulus and hardness of ZTA/Fe45 composite are between Al2O3/Fe45 and ZrO2/Fe45, which are 248.5 GPa and 13.3 GPa, respectively. The ZTA/Fe45 composites exhibit a better impact wear resistance than the other two composites. The impact abrasive wear resistance of the three kinds of composites is positively correlated with the product value of fracture toughness and hardness (H·KIC) of ceramic particles. The wear mechanism of the Fe45 matrix of the composite is micro-furrow and plastic deformation. The brittle fracture and spalling of Al2O3 ceramic particles occur after impact abrasive wear, forming spalling pits and accelerating the wear of Al2O3/Fe45 composites. ZrO2 ceramic particles lead to easy removal from the Fe45 matrix due to lower hardness after impact abrasive wear. ZTA ceramic particles protruded from the surface of the Fe45 matrix after impact abrasive wear. On the surface of ZTA particle, the irregular protuberant steps morphology are formed by SiO2 abrasive impact and tangential wear. The ZTA and ZrO2 ceramic particles in the worn surfaces of the composites undergo t-ZrO2 to m-ZrO2 phase transformation during the impact wear, and the t→m phase transformation content is related to the impact energy. The amount of phase transition increases with the increase of impact energy, When the impact energy is higher than 2J, the amount of phase transition tends to be stable. Under the same impact energy, the amount of t→m phase transition in ZrO2 particles is much lower than that in ZTA. The t→m phase transformation increases the toughness of ZTA particle，improving the impact abrasive wear resistance of ZTA/Fe45 composite.

Effect of two different sulfide coated steel fiber towards tribo performance – An interface study

The purpose of friction material is to decelerate a vehicle by transforming the kinetic energy of the vehicle into heat, via friction, and dissipating that heat to the surroundings. A lot of heat is generated at the contact plateaus formed by the reinforcing fibers. Therefore, inorder to dissipate the heat, steel fibers were coated with FeS and SnS and accordingly brake pads were made and termed as DBF and DBS. Another brake pad with similar formulation but with a mixture of steel fiber, FeS and SnS was made (designated as DBO) for comparison. All three brake pads were tested in an inertia brake dynamometer with a typical schedule. The speed spread (100/50 Kmph) 0.6g and effectiveness variation of all the pads are fallen in the required range. The fade I of DBO is observed 32.8% lesser whereas for DBS and DBF, it is observed10% and 15.7% more than the standard values, respectively. DBF and DBO have shown 25.4% and 39.6% more wear than DBS, respectively. Further, it is observed a more consistent µ during single braking to identify fade during stops in the second effectiveness test. It is evidenced for the increase in the life of the friction film formed by the sulfide coated fibers in DBS which has increased its wear resistance (Max Δµ = 0.10 for DBS, 0.29 for DBF, and 0.30 for DBO). It is also noticed that the radial wear of all three brake pads was greater than the tangential wear and their ratios are 1.36, 1.40 and 1.55, respectively for DBS, DBF and DBO. Moreover, the optimization has revealed the DBS as best performer friction materials formulation.

Pitch bearing/raceway fretting: Influence of contact angle

In this paper, a three-dimensional numerical simulation (using ABAQUS) of the radial and tangential wear between a ball bearing and a raceway is presented. The aim was to study the influence of the contact angle between ball and raceway on the fretting. A range of contact angles was studied with critical parameters such as contact stress, relative slip, plastic deformation, and contact state. The model was validated against experimental data. The results show that with an increase in the contact angle, the area of maximum stress increases, the bearing capacity of the raceway decreases, and the maximum radial stress moves from the sub-surface to the raceway surface. The raceway surface is shown to be prone to peeling and wear, which reduces the service life of the raceway.

Friction and wear performance of the 0.5Ba(Ti0.8Zr0.2)O3-0.5(Ba0.7Ca0.3)TiO3 piezoelectric film

As a lead-free piezoelectric material with potential application, 0.5Ba(Ti0.8Zr0.2)O3-0.5(Ba0.7Ca0.3)TiO3 (BZT-0.5BCT) ceramics, which has a morphotropic phase boundary composition, deserves much attention due to its excellent ferroelectric and piezoelectric properties. BZT-0.5BCT lead-free piezoelectric film has been synthesized on a Si (100) substrate by Sol-Gel process. The topography of the film measured using an atomic force microscope and a scanning electron microscope shows that the surface of the prepared film is smooth, and the grain is in the shape of hemisphere with a diameter of 80-100 nm. The film is 1.7 μm in thickness, with pores inside. Friction experiments show that the friction between the tip and the piezoelectric film is much larger than that between the tip and the SiO2 substrate, because of the existence of electrostatic force between the film and the silicon tip. However, the friction coefficients obtained are approximately equal. Nano-scratch experiments show that the BZT-0.5BCT film has a high normal carrying capacity, but a poor tangential wear resistance. The average elastic modulus of the film is 23.64 GPa ± 5 GPa, and its hardness is 2.7-4 GPa, both being slightly lower than those of the bulk value in PZT ceramics.