Wear and Friction properties of H-Al-17Si alloy with dry, lubrication and coated (DLC-Star) conditions under HFRR

Dry, lubrication (SAE15W40), and coated (DLC-Star) reciprocating tribological tests on rapid solidified AlSi17Cu3.5-4Mg0.6-0.8 alloy was conducted using a high frequency linear reciprocating rig (HFRR) at ambient temperature. The alloy fabricated with the rheo-stir squeeze casting procedure under T-6 condition. However, at different loading (0-30 N) conditions, wear and friction properties of rapid solidified H-Al-17Si alloy are investigated. It is observed that the lower friction coefficient value obtained for DLC-Star coated H-Al-17Si alloy compared to dry and lubrication conditions. Though, for dry and lubricated sliding, the obtained wear coefficient values are 2.9X10-3 mm3/N.m and 4.0X10-4 mm3/N.m. A lower coefficient of wear value of 5.4X10-5 mm3/N.m was recorded with DLC-star coating under dry conditions. The alloy wear coefficient values first increases with applied load (up to 20 N) and then decreases (20 N to 30 N). EDS, AFM surface roughness profilometer, SEM, and advanced metallurgical microscope (AMM) analysis techniques used for the characterization of surface morphologies. The developments in friction and wear coefficients were fundamentally ascribed to the dispersion and size of primary Si elements and the development of tribo-oxide films on the rapid solidified AlSi17 alloy coated (DLC-Star) surfaces.

SOME COMMENTS ON THE INTERPRETATION OF THE TRIBOLOGICAL WEAR COEFFICIENT

An original model of tribological wear is presented, an alternative to the commonly used J.F. Archard’s model. The impossibility is established of a full conversion of mechanical work into the heat of dissipation and thereby of avoiding wear in the sliding friction of solids. The assumption is consequently questioned that only some contacts of surface asperities are subject to temporary wear. Material wastage is assumed to occur at each contact of asperities. The volume of worn material is dependent on the volumetric wear coefficient of the “energy dissipation zone” in friction. The dimensions of the zone are determined in both the elements in friction. Linear wear intensities and volumetric wear are described in analytical terms. The thermodynamic analysis of the tribological process indicates some limitations to these intensities. Energetic efficiencies of solid wear and heating as a result of friction are defined. Some new interpretations of the wear coefficient are proposed.

Experimental Study on the Influence of TiN/AlTiN PVD Layer on the Surface Characteristics of Hot Work Tool Steel

It is desirable to improve tool steel wear resistance to produce pieces with precise dimensions and increase the lifetime of tools. The aim of this work was to modify the surface of 1.2344 (X40CrMoV5-1) hot work tool steel to improve the wear properties. Surface modification was achieved in three steps: first, hardening was applied, followed by plasma nitridation and, finally, physical vapor deposition (PVD) was employed to produce a TiN/AlTiN multilayer coating. The microhardness and the wear coefficient of the surfaces were measured. PVD coating showed the highest hardness value, 2938 HV0,01, whereas plasma nitridation followed by PVD resulted in 2679 HV0,01. The surface modification resulted in an increase in surface roughness in all cases compared to the hardened sample. However, the wear coefficient showed a significant decrease for the surface treated samples. The lowest wear coefficient of K = 1.47 10–10 mm3/Nm, which is a magnitude lower than the reference hardened sample (K = 6.32 10–9 mm3/Nm), was achieved employing both plasma nitridation and PVD. The results confirm that the use of a combined surface modification of plasma nitridation and PVD significantly improve the wear resistance of the treated samples.

Friction and Wear Behavior of a Physical Vapor Deposition Coating Studied Using a Micro-Scratch Technique

CrSiN coating was deposited by physical vapor deposition (PVD) magnetron sputtering on XC100 steel substrate. Microstructural and morphological properties were studied using scanning electron microscopy (SEM)/energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), and atomic force microscopy (AFM). Nanoindentation and scratching experiments were conducted to study the mechanical and adhesion behavior. Multi-pass scratch tests were conducted under different sliding conditions. Results showed that CrSiN coating has a dense and compact nanocomposite microstructure consisting of CrN nanocrystallites and SiN amorphous matrix. The CrSiN thin film exhibit hardness and Young's modulus of 30.52 ± 1.85 GPa and 338.32 ± 13.5 GPa, respectively. The H/E, H3/E2, and 1/HE2 ratios were also calculated (H/E ≈ 0.09, H3/E2 ≈ 0.024, and 1/HE2 ≈ 2.86 × 10−07) and used to predict and assess the elastic/plastic and wear resistance. Critical loads LC1, LC2, and LC3 obtained with scratch test, were, respectively, 11.5 ± 0.12, 16.6 ± 0.23, and 20 ± 0.35 N. Multi-pass scratch were analyzed and the friction coefficient (COF), the damage mechanism, and wear volume were determined. The use of an energetic approach allowed to determine the energetic wear coefficient. CrSiN coating revealed a low friction coefficient (around 0.1) and a low energetic wear coefficient (6.3 × 10−7 mm3/N.m). In addition, it was found that multi-pass scratch method has the potential to extract relevant information about wear behavior.

HOT COMPACTION PROCESS OPTIMIZATION FOR IMPROVEMENT TRIBOLOGY BEHAVIOR OF ZIRCONIUM SILICATE STRENGTHENED BMCS

The paper describes the optimization of the hot compaction process to simultaneously increase hardness and decrease the wear coefficient of zirconium silicate reinforced BMCs. L9 orthogonal array is chosen for setup the experiment. Examining the influencing parameters is carried out on factors such as pressure, temperature, particle size, and particle content. Grey relation analysis is used to investigate to produce an optimal combination of parameter levels. The transmission electron scanning is used to study the morphology of zirconium silicate. The wear coefficient of the specimen was investigated by using the weight loss method. A scanning electron microscope was carried out to evaluate the wear track surface of the composite. The test results show that the particle size is the most influential hot compaction parameter. The optimal conditions for the hot compacting process are the temperature level at 350 °C, the pressure level at the 400 MPa level, the particle content level at 12 % weight, and the particle size level at 80 µm. In this optimal condition, the prediction GR-Grade value is 0.695. The validation test results showed that the GR-Grade value increased by 0.15, the hardness increased by 25%, and the wear coefficient decreased by 53%. This optimization method with Gray Relational Analysis has proven to be effective in the hot compaction process for improving the tribology behavior of the composites.

Impact of Tungsten Incorporation on the Tribomechanical Behavior of AlCrWxSiN Films at Room and Elevated Temperature

AlCrWxSiN thin films (0 ≤ x ≤ 17.1 at.%) were synthesized by means of a hybrid magnetron sputtering process, merging direct current (DC) as well as tungsten high power impulse magnetron sputtering (HiPIMS) supplies. The influences of increasing the tungsten contents on the structural as well as the friction and wear behavior at room and high temperatures (500 °C) were elaborated. As a reference, a W61.4N38.6 system served to analyze synergetic effects on the oxidation behavior. Increased tungsten contents in AlCrWxSiN resulted in more distinctive (200)-, (202)-, and (311)- crystal orientations. A W/Cr ratio of ~1 could be correlated with a denser film growth, the highest hardness (24.3 ± 0.7 GPa), and a significantly decreased wear coefficient (<0.3 × 10−5 mm3/Nm). Tribological tests performed at room temperature revealed that the coefficient of friction decreased with higher tungsten contents to µ~0.35. In contrast, at elevated temperatures, the coefficient of friction increased with higher W concentrations due to spotty oxidations in the wear track, which resulted in a locally increased surface roughness. Finally, a phase transformation of the WN film to m-WO3 did not contribute to a friction reduction at 500 °C.

A Numerical Simulation of Fretting Wear considering the Dynamic Evolution of Debris for the Coated Contact Surface

In this paper, a multi-layer body model in which material properties and wear coefficient change with node coordinates is proposed, so that the wear profile is not restricted by the singularity of the interface of the coated contact pairs. The conversion rate of the adhered particles was obtained to describe the growth and expansion of the debris at the fretting interface based on experiments, and the wear model of coated contact pair considering the dynamic evolution of the debris layer was established. By comparing the previous experimental and computational results, the wear calculation method proposed in this paper is more reasonable to predict the wear profile of the coated contact pair. In addition, the influence of the debris layer on the wear depth, friction width, and contact pressure in the fretting process is analyzed, indicating that the existence of the debris layer can delay the wear process. Finally, the fretting wear life of the SCMV steel contact pair deposited with the W-DLC coating is estimated.

Improving the Quality and Durability of Restorative Coatings by Arc Deposition and Modification with Natural Additive Bentonite Clay

The study considers the possibility of improving the quality and service life of reducing coatings by arc deposition and modifying with natural additive bentonite clay. It has been established that when the modifier is introduced into the fluid bath during arc deposition, the phases and their interactions change. Introduction of the modifying additive bentonite clay significantly changes the crystalline lattice of the carbidephases. The optical-mathematical method revealed the absence of austenite and the pair interaction of ferrite-carbide during modification. The maximum proportion of phases corresponds to ferrite (33.8% -2 times decrease) and ferrite-austenite-carbide interaction (48.62% -2 times increase). The ferrite-austenite interaction increases almost 8 times during modification. The wear coefficient in this case is 2.2 times lower in comparison with the original steel 65Gand 1.4 times lower in relation to arc deposition with only T-620 electrode.

Heat Treatment in an Alloy Al63Cu24Fe12

Aluminum-based alloys containing quasicrystalline phases have good wear resistance due to their low wear coefficient and high hardness. The formation of quasicrystalline phases depends on the composition of the alloy and the imposition of high cooling rates on the molten metal. In the raw state of fusion, presenting β-type and Al13Fe4 monoclinic phases, they are present together with the quasicrystalline phase. A careful chemical composition control and an efficient heat treatment are necessary to obtain quasicrystalline phases. The objective of this work was to study the heat treatment in the homogenization of the quasicrystalline alloy Al64Cu27Fe15 obtained by smelting, in a controlled atmosphere. To understand the microstructural evolution, characterizations were made using SEM and XRD. The thermal treatment carried out for 24 hours, to obtain a microstructure with icosaedral phase coexisting with small increases in existing crystalline phases. Keywords: Quasicrystalline Phases. Microstructural Evolution. Phases of type β and Al13Fe4.