Wear characteristic of in situ synthetic TiB2 particulate-reinforced Al matrix composite formed by laser cladding

In order to improve the wear resistance of an aluminum alloy, an in situ synthesized TiB₂ particulate-reinforced metal matrix composite coating was formed on a 2024 aluminum alloy by laser cladding with a powder mixture of Fe-coated boron, Ti and Al was successfully achieved using a 3-kW CW CO₂ laser. The chemical composition, microstructure and phase structure of the composite clad coating were analyzed by energy dispersive X-ray spectroscopy (EDX), SEM, TEM and XRD. The nanohardness and the elastic modulus of the phases of the coating have been examined. The dry sliding wear behaviour of the coating was investigated using a pin-on-ring machine under four loads, namely 8.9, 17.8, 26.7, and 35.6 N. It has been found that the wear characteristics of cladding were completely dependent on the content and morphology of the TiB₂ particulate and intermetallic in the microstructure and the applied load. At the lowest load (8.9 N), with increasing content of TiB₂ particulate and intermetallic, the wear weight loss of the laser cladding was decreased. At higher loads (17.8, 26.7, and 35.5 N), the 2024 Al alloy exhibited superior wear resistance to the particle-reinforced metal matrix composite cladding.     

Tribological Behavior of an Aluminum Matrix Composite with Al4SiC4 Reinforcement under Dry Sliding Condition

In the present research work, an aluminum-based metal matrix composite with in situ Al₄SiC₄ particles has been developed by the incorporation of TiC particles in commercial aluminum melt through a stir-casting method. Microstructure evaluation in correlation to developed hardness and mechanical properties was performed. Furthermore, the dry sliding wear behavior of commercial aluminum and commercial aluminum–5 vol% Al₄SiC₄ composite was investigated at low sliding speed (1 ms^?1) against a hardened EN 31 disk at different loads. The wear mechanism involved adhesion and microcutting–abrasion at lower loads. On the other hand, at higher loads, abrasive wear involving microcutting along with adherent oxide formation was observed. The overall wear rate increased with load in the alloy as well as in the composite. Moreover, the overall wear rate of the composite was lower than that of the commercial aluminum at all applied loads.` The severe wear region at 39.2 N load in the case of the commercial aluminum–5 vol% Al₄SiC₄ composite was found to be delayed up to a longer sliding distance compared to commercial aluminum. The in situ Al₄SiC₄ particles offered resistance to adhesive wear. Accordingly, the commercial aluminum–5 vol% Al₄SiC₄ composite exhibited superior wear resistance compared to the commercial aluminum.     

Defect intelligent identification in resistance spot welding ultrasonic detection based on wavelet packet and neural network

Experimental correlation between varying processing and wear behaviour of ternary Ni-Co-SiO₂ composites coating was investigated. The parameter used in this research are: SiO₂ (5–25 wt%), thermal treatment (100–300 °C), applied load (5–15 N). The results show that novel ternary Ni-Co-SiO₂ nanoparticle composite coating was successful applied to mild steel. The addition SiO₂ nanoparticles in the coating Ni-Co bath lead to uniform microstructure. Thermal treatment of the coating at 300 °C decreased wear rate by (?0.031), increasing the wt% of SiO₂ from 0 to 25 decreased the wear rate by ?0.018, applied load increases from 5 to 15 N raises the wear rate raises (0.0097), The lower wear rate was obtained at 25 wt% SiO₂, applied load 5 N and thermal treatment at 300 °C. Validation of the results from pin on disc test with electro-hydraulic servo PV friction testing machine shows the same wear pattern. One can concluded in this work that the wear rate of the coated materials depend on the made up of the coating and not on the type of wear mechanism. It have be established in this work that thermal treatment and SiO₂ nanoparticle can be used to enhance the wear behaviour of Ni-Co coating of mild steel.     

Multilayer thin film CrN coating on aerospace AL7075-T6 alloy for surface integrity enhancement

Chromium nitride (CrN) coating has emerged as a new alternative in machining applications. CrN has good thermal stability, low deposition temperature, and excellent wear and corrosion resistance. However, no precise information exists yet regarding the ideal coating parameter conditions that lead to higher surface integrity. For this reason, an optimization study is desired—a study on the parameters of CrN coating on aerospace Al7075-T6 alloy using physical vapor deposition magnetron sputtering. The present research work investigates the effects of temperature as well as nitrogen flow rate and DC power on coated samples’ surface hardness, adhesion, surface roughness, and microstructure. To carry out the investigation, the Taguchi optimization method with L₁₆ (3⁴) orthogonal array was applied. However, to obtain optimum parameters for superior surface integrity, signal/noise (S/N) response analysis method was employed. Finally, confirmation tests with the best parameter combinations attained in the optimization process were carried out to demonstrate the progress made. Ultimately, surface hardness of coated Al7075-T6 was enhanced by 15.33 %, adhesion by 24.3 %, and surface roughness by 7.22 %.     

Tribological behaviour and wear mechanism of MoS2–Cr coatings sliding against various counterbody

MoS₂–Cr coatings with different Cr contents have been deposited on high speed steel substrates by closed field unbalanced magnetron (CFUBM) sputtering. The tribological properties of the coatings have been tested against different counterbodies under dry conditions using an oscillating friction and wear tester. The coating microstructures, mechanical properties and wear resistance vary according to the Cr metal-content. MoS₂ tribological properties are improved with a Cr metal dopant in the MoS₂ matrix. The optimum Cr content varies with different counterbodies. Showing especially good tribological properties were MoS₂–Cr8% coating sliding against either AISI 1045 steel or AA 6061 aluminum alloy, and MoS₂–Cr5% coating sliding against bronze. Enhanced tribological behavior included low wear depth on coating, low wear width on counterbody, low friction coefficients and long durability.     

Wear Behaviour of In Situ Al/TiB<Subscript>2</Subscript> Composite: Influence of the Microstructural Instability

In this present work, the in situ Al (A380)/5 wt%TiB₂ composites were fabricated through salt–melt reaction using halide salts such as potassium hexafluorotitanate (K₂TiF₆) and potassium tetra fluoroborate (KBF₄) salts as precursors. The composites were produced at four different melt temperatures (700, 750, 800, 850 °C). The formation of particle was confirmed from XRD results. The wear behaviour of Al/5 wt% TiB₂ composite was investigated by varying the wear test parameters such as sliding temperature (25, 100, 150, 200 °C), applied load (10, 20, 30, 40 N), sliding velocity (0.4, 0.7, 1, 1.3 m/s). The microstructure of Al/5 wt% TiB₂ composite was correlated with the wear characteristics of the composites. The wear resistance of Al/5 wt% TiB₂ composite was significantly improved due to the presence of TiB₂ particle in Al matrix material. The composite produced at melt temperature 800 °C showed a higher wear resistance at applied load: 10 N, sliding temperature: 25 °C and sliding velocity: 0.7 m/s. The wear mechanism for each of the tested condition was identified from the worn surfaces using scanning electron microscopy (SEM). ANOVA test was carried out to find out significant factor for the wear resistance of composite. The checking of adequacy of experimental value for the wear behaviour of composite for different testing condition was analysed by residual plots using statistical software.     

HVOF-Sprayed Adaptive Low Friction NiMoAl–Ag Coating for Tribological Application from 20 to 800 °C

An adaptive NiMoAl–Ag composite coating was deposited by high-velocity oxy fuel spraying, and its tribological properties from 20 to 800 °C under unlubricated conditions were evaluated using a CSM high-temperature tribometer. Scanning electron microscopy, X-ray diffraction and Raman spectroscopy were used to characterize the coating and corresponding wear tracks to determine the lubrication mechanisms. The results showed that the friction coefficient of the NiMoAl–Ag composite coating was around 0.3 from 20 to 600 °C and reached the lowest value of 0.09 at 800 °C. Meanwhile, wear rates of the coating were maintained on the order of 10^?5 mm³/N m at the test temperatures except for 400 and 600 °C. Characterization of the NiMoAl–Ag coating revealed that silver provided lubrication below 400 °C. Ag₂Mo₂O₇ and Ag₂MoO₄, which were formed through tribochemical reactions, acted as high-temperature lubricants above 400 °C. It was especially proposed that silver in a nearly molten state was effective in reducing the friction of the NiMoAl–Ag coating at 800 °C. Moreover, a comprehensive lubrication mechanism model of an NiMoAl–Ag composite coating at 800 °C was established to explain the extremely low friction coefficient and wear rate of the coating.     

Dry Sliding Friction and Wear Characteristics of Cu-Sn Alloy Containing Molybdenum Disulfide

The wear and sliding friction response of a hybrid copper metal matrix composite reinforced with 10 wt% of tin (Sn) and soft solid lubricant (1, 5, and 7 wt% of MoS₂) fabricated by a powder metallurgy route was investigated. The influence of the percentages of reinforcement, load, sliding speed, and sliding distance on both the wear and friction coefficient were studied. The wear test with an experimental plan of six loads (5–30 N) and five sliding speeds (0.5–2.5 m/s) was conducted on a pin-on-disc machine to record loss in mass due to wear for two total sliding distances of 1,000 and 2,000 m. The results showed that the specific wear rate of the composites increased at room temperature with sliding distance and decreased with load. The wear resistance of the hybrid composite containing 7 wt% MoS₂ was superior to that of the other composites. It was also observed that the specific wear rates of the composites decreased with the addition of MoS₂. The 7 wt% MoS₂ composites exhibited a very low coefficient of friction of 0.35. The hardness of the composite increased as the weight percentage of MoS₂ increased. The wear and friction coefficient were mainly influenced by both the percentage of reinforcement and the load applied. Wear morphology was also studied using scanning electron microscopy and energy-dispersive X-ray analysis.     

Friction and Wear Behavior of WS2/Zr Self-lubricating Soft Coatings in Dry Sliding Against 40Cr-Hardened Steel Balls

WS₂ and WS₂/Zr self-lubricating soft coatings were produced by medium-frequency magnetron sputtering, multi-arc ion plating and ion-beam-assisted deposition technique on the cemented carbide YT15 (WC + 15 % TiC + 6 % Co) substrates. Microstructural and fundamental properties of these coatings were examined. Sliding wear tests against 40Cr-hardened steel using a ball-on-disk tribometer method were carried out with these coated materials. The friction coefficient and wear rates were measured with various applied loads and sliding speeds. The wear surface features of the coatings were examined using SEM. The results showed that the WS-1 specimen (with WS₂/Zr composite coating) has higher hardness and coating/substrate critical load compared with that of the WS-2 specimen (only with WS₂ coating). The friction coefficient of WS-1 specimen increases with the increase in applied load and is quite insensitive to the sliding speed. The wear rate of the WS-1 specimen is almost constant under different applied loads and sliding speeds. The WS-1 specimen shows the smallest friction coefficient and wear rate among all the specimens tested under the same conditions. The WS-1 specimen exhibits improved friction behavior to that of the WS-2 specimen, and the antiwear lifetime of the WS₂ coatings can be prolonged through adding Zr additives. The self-lubricating and wear mechanism of the WS₂/Zr coating was also found from the sliding wear tests.     

Microstructure,tribological and mechanical strengthening effect of multiphase Zn/ZrO<Subscript>2</Subscript>-SiC electrodeposited composite coatings

In an attempt to improve the mechanical and thermal resilient properties of mild steel, Zn-ZrO₂-SiC composite coating was fabricated from zinc-based sulphate electrolyte with incorporated composite particles of ZrO₂/SiC at 2.0 A/cm² for 10 min. The effects of particle on the mechanical properties were examined using scanning electron microscope attached with energy dispersion spectroscopy and atomic force microscopy. The micro-hardness and wear resistance behaviour were determined with high diamond micro-hardness tester and three body abrasive MTR-300 testers with dry sand rubber wheel apparatus with 5 N. The fabricated coating was thermally heated at 200 °C for 4 h to evaluate the coating stability. From the results, a modification in the microstructure and topographic orientation as a result of incorporated composite was noticed on the zinc matrix. The mechanical and thermal properties were observed to be considerably improved by the incorporation of the ZrO₂/SiC weight fraction. A significant improvement in wear and hardness properties were also obtained for the multiphase embedded coatings.     

Multi-response optimization using the Taguchi-based grey relational analysis: a case study for dissimilar friction stir butt welding of AA6082-T6/AA5754-H111

This paper presents a multi-response optimization process for dissimilar friction stir welding of AA6082/AA5754 aluminum alloys. An L₉ orthogonal array was constituted for the experiments. Three welding parameters—tool shoulder diameter-to-pin diameter (D/d) ratio, tool rotational speed (TRS), and welding speed (WS)—were associated with tensile strength and elongation. An optimization process was started to determine the signal-to-noise (S/N) ratio. Grey relational analyses were performed utilizing the S/N ratio. According to the results of a series of analyses, the optimal welding condition was determined as 4 for D/d, 1,000 rpm for TRS, and 100 mm/min for WS. The analysis of variance results showed that all the welding parameters are statistically significant at 95 % confidence level. Additionally, the joint efficiency of welding fabricated at the optimal condition was compared for both AA6082 and AA5754. This revealed that the joint efficiency is 66 % for AA6082 and 92 % for AA5754.     

Mechanical and tribological properties of Cr–Nb double-glow plasma coatings deposited on Ti–Al alloy

Double-glow plasma (DGP) coatings are recommended for metallic components to mitigate the damage induced by complex working conditions in previous studies. In this paper, Nb-rich (Cr–Nb₄) and Cr-rich (Cr₄–Nb) -alloyed layers were formed onto the Ti–Al substrate via a DGP process to enhance its wear resistance. Scratch and Nano-indentation tests were used to evaluate the mechanical properties of the coatings. The tribological behaviour of the coatings were investigated using a pin-on-disc tribometer by rubbing against the GCr15 ball. Results from surface analysis techniques showed that the coatings mainly comprised Cr, Nb and Cr₂–Nb phases, and were well bonded to the substrate. The hardness of the Cr–Nb₄ coating was 11.61GPa and the Cr₄–Nb coating was 9.66 GPa which all higher than that of the uncoated Ti–Al which was 5.65 GPa. However, the critical load of the Cr₄–Nb coating ~21.64 was higher than that of the Cr–Nb₄ coating ~17.6. And the specific wear rate of Cr–Nb₄ coating, Cr₄–Nb coating and uncoated Ti–Al were 3.54 × 10^?4, 0.01 × 10^?4 and 1.53 × 10^?4mm³ N^?1 m^?1_, respectively. The low-wear mechanism of the coatings is discussed in detail in this paper.     

Improvement of the Oxidation and Wear Resistance of Pure Ti by Laser-Cladding Ti<Subscript>3</Subscript>Al Coating at Elevated Temperature

Ti₃Al coating was in situ synthesized successfully on pure Ti substrate by laser-cladding technology using aluminum powder as the precursor. The composition and microstructure of the prepared coating were analyzed by transmission electron microscopy, scanning electron microscopy (SEM), and X-ray diffraction technique. Thermal gravimetric analysis was used to evaluate the high-temperature oxidation resistance of the Ti₃Al coating. The friction and wear behavior was tested through sliding against Si₃N₄ ball at elevated temperature of 20, 100, 300, and 500°C. The morphologies of the worn surfaces and wear debris were also analyzed by SEM and three-dimensional non-contact surface mapping. The results show that the Ti₃Al coating with high microhardness, high-temperature oxidation resistance, and high temperature wear resistance. The pure Ti substrate is dominated by severe adhesion wear, abrasive wear, fracture, and severe plastic deformation at lower temperature, and severe adhesion wear, abrasive wear, plastic deformation, oxidation, and nitriding wear at higher temperature, whereas the Ti₃Al coating experiences only moderate abrasive and adhesive wear when sliding against the Si₃N₄ ceramic ball counterpart. In addition, the wear debris of the laser-cladding Ti₃Al coating sliding and Si₃N₄ friction pairs are much smaller than that of pure Ti substrate and Si₃N₄ friction pairs at elevated temperature.     

Fabrication and testing of Al–SiCp composite poppet valve guides

Composite materials are replacing the materials used in various fields and are the candidate materials for future growth. Metal matrix composites are the class of composite materials finding vast applications in automotive, aircraft, defense, sports, and appliance industries. In the present work, Al–SiC_p composites with 5–30 wt.% of SiC particulates were fabricated using powder metallurgy as well as casting processes. Mechanical alloying of aluminum and SiC particles was done prior to compaction so as to enhance the properties of the fabricated powder metal components. A custom built sliding valve guide wear test rig was fabricated to simulate the valve stem/guide wear under cold start condition of an engine by reciprocation of a valve stem under different imposed loads, against a stationary poppet valve guide. The hardness and radial crushing load was measured for the Al–SiC_p composite poppet valve guides and were found better than the cast iron poppet valve guides presently used in engines. The wear test of the poppet valve guides was done using valve guide wear test rig, which revealed that the Al-20 wt.% SiC_p and Al-30 wt.% SiC_p composite poppet valve guides have higher wear resistance than the cast iron poppet valve guides. The hardness, radial crushing load, and wear resistance of Al–SiC_p composite poppet valve guides were found to increase with increase in weight percent of SiC_p. The microstructural analysis of the cast and PM Al–SiC_p composites was also done using scanning electron microscope. Finite element analysis of the Al–SiC_p composite poppet valve guide was also done using Ansys software, which supports the successful implementation of the Al–SiC_p composite poppet valve guides for automobiles.     

Tribological properties of Ni3Al-Cr7C3 composite coating under water lubrication

The tribological properties of Ni₃Al-Cr₇C₃ composite coating under water lubrication were examined by using a ball-on-disc reciprocating tribotester. The effects of load and sliding speed on wear rate of the coating were investigated. The worn surface of the coating was analyzed using electron probe microscopy analysis (EPMA) and X-ray photoelectron spectroscopy (XPS). The results show the friction coefficient of the coating is decreased under water lubrication. The wear rate of the coating linearly increases with the load. At high sliding speed, the wear rate of the coating is dramatically increased and a large amount of the counterpart material is transferred to the coating worn surface. The low friction of the coating under water lubrication is due to the oxidizing of the worn surface in the wear. The wear mechanism of the coating is plastic deformation at low normal load and sliding speed. However, the wear mechanism transforms to microfracture and microploughing at high load with low sliding speed, and oxidation wear at high sliding speed. It is concluded that the contribution of the sliding speed to an increase in the coating wear is larger than that of the normal load.     

Parametric study of the dry sliding wear behaviour of AA6082-T6/SiC and AA6082-T6/B<Subscript>4</Subscript>C composites using RSM

In this paper a parametric study of the wear behaviour of Aluminum matrix composites has been carried out. AA6082-T6/SiC and AA6082-T6/B₄C composites were fabricated using stir casting technique. The percentage of reinforcement was taken as 5, 10, 15 and 20 wt.% for both SiC and B₄C particulates. Dry sliding wear tests were conducted using pin-on-disc apparatus at room temperature and process optimization was done using Response surface methodology (RSM). Weight percentage (wt.%) of reinforcement, sliding speed, load and sliding distance were the four process parameters considered to analyse these composites wear behaviour. Analysis of variance (ANOVA) showed that sliding distance exerted the highest contribution (60.24 %) to AA6082-T6/SiC wear, followed by sliding speed (14.28 %), load (11.88 %) and reinforcement content (4.31 %). The same trend was found in AA6082-T6/B₄C composites with slightly different contribution values, namely sliding distance (63.28 %), sliding speed (14.02 %), load (10.10 %) and reinforcement content (4.05 %). RSM analysis revealed that increases in the reinforcement content and sliding speed reduce the wear rate in both composites. On the other hand, increases in load and sliding distance led to higher AA6082-T6/SiC and AA6082-T6/B₄C composites wear. The two predictive models were validated by conducting confirmation tests and certified that the developed wear predictive models are accurate and can be used as predictive tools for wear apllications.     

Characteristics of Al alloy surface after EDC with sintered Ti electrode and TiN powder additive

Electrical discharge coating (EDC) performs not only machining but also surface modification of workpiece by changing the polarity of the electrode and dielectric medium. As a candidate of metal bipolar plate in proton exchange membrane fuel cell application, machined Al alloy needs surface coating to overcome its poor corrosion resistance. The goal of this study was to investigate the coating characteristics of 6061-T6 aluminum (Al) alloy machined using titanium (Ti)-sintered electrodes in wet and dry EDC. The results show that in wet EDC using cathodic T-8 sintered electrode, both material removal rate (MRR) and tool wear rate (TWR) were kept reasonably low. Discharge current (I _p) and pulse duration (T _on) are the main determinants of the morphology of the EDCed Al alloy surface. The appropriate parameters for wet EDC are found to be 1 A?<?I _p?<?8 A and 9 μs?<?T _on?<?100 μs at DF?=?27 %. Adding TiN powder to kerosene not only improved the EDCed surface quality but also decreased the coefficient of friction. The formation of a TiC layer on the machined surface prolonged the onset of friction transition, which would in turn enhance the wear resistance of the machined surface. However, no TiN layer was formed during wet EDC. On the other hand, in dry EDC using anodic T-6 and T-8 sintered electrodes, both MRR and TWR were below zero. A pure TiN layer of 20-μm thickness was deposited on the EDCed surface and featured good spallation resistance. The appropriate dry EDC parameters for forming a pure TiN layer on a workpiece surface are found to be 1 A?<?I _p?<?30 A and 6 μs?<?T _on?<?72 μs at DF?=?16 %. From the experimental results of this study, the application of EDC to surface modification during fabrication of the fluid pattern on an Al metal bipolar plate can be expected.     

Synthesis of TiB2-reinforced iron-based composite coating

Titanium diboride (TiB₂) particulate reinforced Fe-based alloy composite coating was produced with ferrotitanium (FeTi), ferroboron (FeB), ferrotungsten (FeW), ferrochromium (FeCr), ferrovanadium (FeV) and ferromolybdenum (FeMo) powders by using gas tungsten arc welding (GTAW) process. The effects of GTAW processing on the microstructure of AISI-4340 alloy coating with ferro-alloy powders were investigated experimentally. Abrasive wear tests were performed on the coated surface of samples to examine the influence of vol% and the size of boride on wear rates. Depending on the results, it was seen that the samples coated by FeTi-FeW-FeB ferro-alloy powders mixture have the highest wear resistance.     

Role of zirconium diboride particles on microstructure and wear behaviour of AA7075 in situ aluminium matrix composites at elevated temperature

ABSTRACT

The present research work examines the impact of temperature on the dry sliding wear behaviour of AA7075 aluminium strengthened zirconium diboride (ZrB₂) particulate composite (0, 3, 6, 9 and 12?wt.%). The dry sliding wear behaviour of the AMCs was inspected utilizing a pin-on-disc machine at differing temperatures (40, 60, 120, 180 and 240°C). The wear resistance of AMCs improved with the increased substance of ZrB₂ particulates at all test temperatures. The worn surface of the AMC pins was described utilizing FESEM. It was found from the SEM micrographs of worn surface, that at different temperatures, adhesion and metal flow were the prime wear process of the AA7075 composites, while for in situ formed AMCs, metal stream and oxidation were the factors affecting the wear process. The worn surface of the AMCs showed that there was a modification in wear component from abrasive wear to metal flow.     

Microstructure and Tribological Properties of a HfB<Subscript>2</Subscript>-Containing Ni-Based Composite Coating Produced on a Pure Ti Substrate by Laser Cladding

A HfB₂-containing Ni-based composite coating was fabricated on Ti substrates by laser cladding, and its microstructure and tribological properties were evaluated during sliding against an AISI-52100 steel ball at different normal loads and sliding speeds. The morphologies of the worn surfaces were analyzed by scanning electron microscopy (SEM) and three-dimensional non-contact surface mapping. The results show that wear resistance of the pure Ti substrate and NiCrBSi coating greatly increased after laser cladding of the HfB₂-containing composite coating due to the formation of hard phases in the composite coating. The pure Ti substrate sliding against the AISI-52100 counterpart ball at room temperature displayed predominantly adhesive wear, abrasive wear, and severe plastic deformation, while the HfB₂-containing composite coating showed only mild abrasive wear and adhesive wear under the same conditions.