Alloy Friction Research Articles

Friction and Wear Behavior of C17200 Copper-Beryllium Alloy in Dry and Wet Environments

Friction and Wear Behavior of C17200 Copper-Beryllium Alloy in Dry and Wet Environments

Tribological Performance of Artificial CoCrMo Prosthesis by ELID Grinding Process

The demand for CoCrMo alloy as an artificial prosthesis has increased for its reliable properties. However, machining of CoCrMo alloy is challenging due to meet the high requirements on prosthesis’ surface quality. In this paper, a new approach of fine ELID grinding on CoCrMo alloy has been proposed using a Kistler three-component dynamometer to monitor the grinding force in real time. This paper also presents the friction and wear performance of CoCrMo alloy. Results show that better efficiency and surface quality can be obtained with low feed speed and small grinding depth. The passivation layer was found on the surface of CoCrMo alloy after ELID grinding, which makes the CoCrMo alloy prosthesis have better biocompatibility. The wear resistance test has proved that CoCrMo alloy has better wear resistance and lower wear quality and is suitable for manufacturing prosthesis.

Tribological Performance of Gradient Ag-Multilayer Graphene/TC4 Alloy Self-Lubricating Composites Prepared By Laser Additive Manufacturing

Based on a functionally graded material (FGM) design concept, the laminated-graded Ag-multilayer graphene/TC4 alloy self-lubricating composites (GTMAC) were prepared to overcome the poor friction and wear behaviors of TC4 alloy and expand engineering applications where friction is involved. Tribological experiments on GTMAC were carried out under different temperatures and loads in contrast with TC4 alloy (TC4) and homogeneous Ag-multilayer graphene/TC4 alloy self-lubricating composites (TMAC). The results show that GTMAC presents better friction and wear behaviors compared with TC4 and TMAC over a broad range of temperatures and loads. This is because of the synergistic effect of Ag and multilayer graphene, which are crushed and spread out in the sliding process, resulting in the formation of a lubricating film on the worn surface. Additionally, the equivalent stress distributions on the friction surfaces of TMAC and GTMAC are investigated using a finite-element method. The simulation results indicate that the GTMAC sample model with a smaller equivalent stress can avoid the occurrence of cracks and peeling of the surface material, so the the lubricating film is formed easily and remains for a longer working time.

The Influence of Tool Shape and Process Parameters on the Mechanical Properties of AW-3004 Aluminium Alloy Friction Stir Welded Joints.

The purpose of the following study was to compare the effect of the shape of a tool on the joint and to obtain the values of Friction Stir Welding (FSW) parameters that provide the best possible joint quality. The material used was an aluminium alloy, EN AW-3004 (AlMn1Mg1). To the authors’ best knowledge, no investigations of this alloy during FSW have been presented earlier. Five butt joints were made with a self-developed, cylindrical, and tapered threaded tool with a rotational speed of 475 rpm. In order to compare the welding parameters, two more joints with a rotational speed of 475 rpm and seven joints with a welding speed of 300 mm/min with the use of a cylindrical threaded pin were performed. This involved a visual inspection as well as a tensile strength test of the welded joints. It was observed that the value of the material outflow for the joints made with the cylindrical threaded pin was higher than it was for the joints made with the tapered threaded pin. However, welding defects in the form of voids appeared in the joints made with the tapered threaded tool. The use of the cylindrical tool resulted in higher values for about 37% of mechanical properties compared with the highest result for the tapered threaded joint. As far as the parameters were concerned, it was concluded that most of the specimens were properly joined for a rotational speed of 475 rpm. In the joints made with a welding speed of 300 mm/min, the material was not stirred properly. The best joint quality was given for a rotational speed of 475 rpm as well as a variety of welding speed values between 150 and 475 mm/min.

Parametric Optimization of Mechanical Properties via FSW on AA5052 Using Taguchi Based Grey Relational Analysis

The Friction stir processing benefits of aluminium composites contain advanced exploration in the region of aluminium alloy Friction Stir Welding - FSW. The modern advancements in Friction Stir Welding are concentrated on the optimization of welding parameters for multi response attributes. The investigations were carried out with the tool pin profiles, tool rotational speed and traverse speed as predictable process parameters for multi response optimization in Friction Stir Welding of 5052 aluminium alloy. GRG (grey relational grade) was obtained by the grey relational analysis of the friction stir welding process through different qualities, particularly, UTS-ultimate tensile strength and micro hardness. The significant process variables on GRG and most substantial parameters traverse speed and tool pin profiles are examined by ANOVA. Excluding tool rotational speed, tool pin profiles and traverse speed were likewise observed to be significant. To approve the investigation, verification of tests was completed at optimal parameters arrangement and predicted outcomes were observed to be in great concurrence with test values.

Investigation on friction and wear performance of laser cladding Ni-based alloy coating on brake disc

Wear is the leading cause of brake disc failure. However, laser cladding technology provides a fast and environmentally friendly method to repair brake disc damage caused by wear. In this paper, Ni-based alloy powder was used to prepare the coating on the surface of the brake disc to improve its wear resistance, and the coating prepared by laser cladding was systematically studied. The main phases of the coating were γ-Ni and Ni3C, which were the main reasons for increasing the hardness and elastic modulus. The microstructure of the coating is compact. With the change of the solidification rate and temperature gradient, the microstructure changed from columnar to cellular, dendritic and equiaxed. By comparing the wear volume of the coating and substrate before and after wear, it was found that the coating has better wear resistance (about 1.5 times that of the substrate). Besides, the coating also has good oxidation resistance. The oxidation film formed during the wear process of the coating is beneficial to inhibit the regeneration of oxide. Therefore, according to the test results the laser cladding Ni-based coating is an effective means to improve the tribological properties of the brake disc.

Analysis of Variance of Dissimilar Cu-Al Alloy Friction Stir Welded Joints with Different Offset Conditions

In this investigation, dissimilar material AA6061-T6 and Cu B370 were joined by friction stir welding (FSW). This paper presents a feasibility study of FSW to join Al-alloy and Cu-alloy. The experiment was conducted using general full factorial design by varying the tool rotation speed, weld speed, and probe offset, and by keeping the plunge depth constant. In this research work, a statistical model was established to build a connection between the process variables and outcomes—yield strength (YS), ultimate tensile strength (UTS) and % elongation (% E). Statistical tools such as analysis of variance and scatter diagrams were employed to evaluate the suitability of the models. In addition, the impacts of the process variables on the tensile properties were investigated. From the experimental results, it can be concluded that (i) an excellent weld joint could be obtained by keeping the softer Al plate at the retreating side with a probe offset of 2.0 mm towards the softer material, and (ii) maximum tensile properties were obtained at a higher tool-rotation speed, weld speed, and with a probe offset of 2.0 mm. Further, the fractured tensile specimens were investigated using a scanning electron microscope (SEM). From the analyses, it was noted that, during the tensile test, the weld joint failed with a brittle–ductile mixed fracture mode.

Effect of high pressure torsion process on the microhardness, microstructure and tribological property of Ti6Al4V alloy

• Bulk nanostructured Ti6Al4V alloy with average grain size of about 50 nm was obtained by HPT process at 7.5 GPa. • Microhardness was greatly increased and saturated to about 430 hv after 10 HPT revolutions. • For the first time, influence of HPT process on the tribological properties of Ti6Al4V alloy was conducted. • Ti6Al4V alloy had good potential into structural applications due to its remarkably improved mechanical and tribological properties. In the present study, a fully lamellar Ti6Al4V alloy was severely deformed by high pressure torsion (HPT) process under a pressure of 7.5 GPa up to 10 revolutions. Experimental results revealed that the microhardness of Ti6Al4V was increased remarkably by about ∼ 41% and saturated at about 432 Hv after the HPT process. A relatively uniform bulk nanostructured Ti6Al4V alloy with an average grain size of about 52.7 nm was obtained eventually, and no obvious formation of metastable ω phase was detected by XRD analysis. For the first time, the tribological properties of the HPT processed Ti6Al4V alloy were investigated by a ball-on-disc test at room temperature under a dry condition. It was found that HPT process had a great influence on the friction and wear behaviors of Ti6Al4V alloy. With increasing the number of HPT revolutions, both friction coefficient and specific wear rate were obviously decreased due to the reduction of abrasion and adhesion wears. After being deformed by 10 HPT revolutions, the friction coefficient was reduced from about 0.49 to 0.37, and the specific wear rate was reduced by about 48%. The observations in this study indicated that HPT processed Ti6Al4V alloys had good potential in structural applications owing to their greatly improved mechanical and tribological properties.

Revealing the structural heterogeneity of metallic glass: Mechanical spectroscopy and nanoindentation experiments

Microstructural heterogeneity is an important issue in understanding the mechanical and physical properties of metallic glasses (MGs). Theoretically, physical aging below the glass transition temperature relax the MGs systems to a lower potential energy state on the potential landscape (PEL) while the cold rolling rejuvenates MGs to a higher potential energy state. In the current work, we systemically turned the structural heterogeneity through dynamic mechanical relaxation and rejuvenation. Correlations among the structural heterogeneity, internal friction, and shear transformation zones (STZs) of the model alloy was connected. Based on the cooperative shear model and statistical analysis, the scale variation of the STZs was revealed. This study demonstrated that the spatial structural heterogeneity can be enhanced by severe plastic deformation which can reduce the energy barrier for STZs activation. And we proposed the barriers decrease and more nucleation sites of STZs from physical aging to rejuvenation, which may be potential mechanism for improving the plasticity in MGs.

Frequency Dependence of the Internal Friction of the AMg6 Alloy

Frequency Dependence of the Internal Friction of the AMg6 Alloy

Strength and fracture behavior of AA2A14-T6 aluminum alloy friction stir welded joints

The formations and fracture behavior of the AA2A14-T6 aluminum alloy friction stir welded (FSWed) joints are investigated under different ratios of rotational speed to welding speed (n/v). The relationship between the viscous layer (δ) and the rheological layer (ξ) is the key factor to determine the welding quality of joints. When δ < ξ, loose microstructure, needle-like, dispersive, or through void is generated in the joint as the n/v decreases. When δ ≥ ξ, the defect-free joints can be obtained. The through void greatly weakens the tensile properties, and the tensile specimens fracture in the stir zone (SZ). Other defects mainly influence the ultimate strength and the elongation, and the joints fracture at the SZ/thermo-mechanically affected zone or the base material/heat-affected zone (BM/HAZ). The defect-free joints have the largest tensile properties and fracture at the BM/HAZ. Based on the above analysis, the reasonable quality assessment criteria of the FSWed joint need to combine with four aspects: internal formation, strength, plasticity, and fracture behavior. Meanwhile, according to the reasonable matching relationship between δ and ξ, the critical conditions of FSW process parameters for the 2A14-T6 aluminum alloy can be obtained.

Triboinformatic modeling of dry friction and wear of aluminum base alloys using machine learning algorithms

Data-driven methods including machine learning (ML) algorithms can yield a better understanding of how tribological and material properties correlate. Correlations of friction and wear of aluminum (Al) base alloys with their material properties (hardness, yield strength, tensile strength, ductility, silicon carbide content), processing procedure, heat treatment, and tribological test variables (sliding speed, sliding distance, and normal load) studied using traditional and data-driven approaches. Five different ML algorithms, K Nearest Neighbor (KNN), Support Vector Machine (SVM), Artificial Neural Network (ANN), Random Forest (RF), and Gradient Boosting Machine (GBM) applied to experimental tribological data to predict the coefficients of friction (COF) and wear rates. Through performance analysis, we demonstrated that the ML models can satisfactorily predict friction and wear of Al alloys from material and tribological test variables data. Comparative analysis of model performance illustrated that RF outperformed other ML models in wear rate prediction, while KNN exhibited the best performance in COF prediction. Feature importance analysis further revealed that normal load, hardness, and sliding speed have the maximum influence in predicting the wear rate of the alloys. The variation in hardness of the alloys and sliding distance influenced the COF prediction the most.

Effect of rotation speed on microstructure evolution and mechanical properties of nugget zone in 2195-T8 Al-Li alloy friction stir welding joints

Complicated plastic deformation and welding temperature were generated in the nugget zone (NZ) of friction stir welding (FSW) joints leading to different regions being developed, such as shoulder influence zone (SIZ), pin influence zone (PIZ) and swirl zone (SZ). To find the effect of rotation speed on microstructure evolution and mechanical properties of these regions during friction stir welding, serials of AA2195-T8 plates with 7.5 mm thickness were fabricated using different rotation speeds (500, 700 and 900 rpm) and a constant welding speed (50 mm/min). Microstructural characterization was conducted out using electron back scattered diffraction (EBSD), differential scanning calorimetry (DSC), transmission electron microscopy (TEM) and X-ray diffraction (XRD) technologies. Mechanical properties were measured by micro-hardness and tensile test. The results show that grains in the SIZ were mainly shown in wedge-shaped structure and had the high density of low angle boundaries (LABs) showing dominant (100) orientation. However, in the PIZ and SZ, fine and equiaxed grains with dominant (111,101) orientation were observed. With rotation speed increasing, the fraction of LABs increased in the SIZ but showed little changes in the PIZ and SZ. After welding, a large number of T1 and θ′ precipitates almost be completely dissolved in the NZ with many fine δ′/β′ being re-precipitated. It is notable that a few T1 precipitates were observed in the SIZ at a higher rotation speed (900 rpm), which were re-precipitated from the Al matrix after dissolution. In the SIZ, the dominant contribution to yield strength was dislocation strengthening which enhanced with rotation speed increasing. However, in the PIZ and SZ, grain refinement strengthening was the primary strength mechanism, which decreased with rotation speed increasing.

Wear and Corrosion Behavior of Cryogenic Friction Stir Processed AZ31B Alloy

This research work investigated the influence of friction stir processing under cryogenic treatment on the wear and corrosion behavior of an extruded AZ31B alloy. The experimental work that employed rotational speeds of 800, 1000, and 1200 rpm have been used, keeping the tool feed rate constant at 60 mm/min. The wear mechanism of the AZ31B alloy and cryogenic friction stir processed specimens were studied using a high magnification of SEM images. A lower wear rate was attained under cryogenic conditions which are around 20% better than the base metal. The results revealed the achievement of a lower corrosion rate at the rotational speed of 1000 rpm. The presence of fine grains and the absence of defects in the processed region lead to higher hardness.

Tests of a novel re-centering damper with SMA rods and friction wedges

This research focused on development of a new type of re-centering damper consisting of the Ni-Ti Shape Memory Alloy (SMA) rods and friction wedges. Compared with the other existing types of SMA-based dampers, the proposed damper offers an improved energy absorption capacity. In addition, strength and deformation capacity of the proposed damper can be conveniently adjusted if needed. To verify the perceived benefits of the damper, a series of tests were performed on an experimental specimen. It was found that the proposed damper can exhibit stable hysteretic energy dissipation response and reliable re-centering performance without developing any visible damage in the damper components. The test results also show that the damper is not sensitive to the different loading protocols imposed. Beyond the experimental work, a theoretical model for the proposed damper was established and validated by the test results. The theoretical model can be used to design the damper in the future. Furthermore, a three-dimensional computer model was developed for the tested damper. The computer model was found to be able to accurately replicate the nonlinear responses of the experimental specimen. The modelling approaches and assumptions adopted in the computer model can be used for future analysis and design.

Tribological performance of Ti nanolayer coating post plasma nitriding treatment on Co based alloy

Surface treatments via plasma nitriding process have been applied on Co based alloys due to the surface enhancement on their tribological properties. Herein, the surface characteristics to apply a thin Ti coating on biocompatible CoCr ASTM F75–18 alloy samples post-plasma nitriding treatment to improve the mechanical and tribological properties were investigated. A single nanolayer Ti coating was deposited by thermal evaporation technique and posterior plasma nitriding process using three temperatures ranging from 450 °C to 550 °C, considering two processing time of 3 h and 5 h. The samples were characterized using metallographic techniques, energy dispersive spectroscopy, scanning electron microscopy, X-ray diffraction, atomic force microscopy, nanohardness tests under cyclic loads of 20 Hz, 50 Hz and 100 Hz using a load of 350 μN and roughness. Friction and wear characteristics were investigated on pin-on-disc tribometer under dry and lubricated sliding condition. The results showed that Ti coatings post-nitriding process have a beneficial effect on the friction and wear resistance of CoCr alloy depending on the elastic modulus and hardness as well as the contact stiffness under cyclic loads as function of increase the thermal process.

Investigation on the effect of different friction stir machining tools shape on the mechanical properties of magnesium alloy work piece

Friction stir process (FSP) is a method of solid-state consolidation that uses an inexhaustible tool to increase the modification of work piece structural. This current work presents a study of friction stir process on magnesium (Mg) alloy work piece using different design of pin profiles tool. Experiments were conducted in dry condition where tool progression was monitored carefully in every milling passes, then the effect and quality criterion were measured. Result shows that the dominant tool of friction stir process mechanism of mild steel tool is the strength intensity increased at higher speed and lower plunge length due to the superiority of friction stirred region on the magnesium. Furthermore, the hardness of the stirred friction of Mg alloy also increased by using a triangle pin profile design.

Avoiding abnormal grain growth in thick 7XXX aluminium alloy friction stir welds during T6 post heat treatments

Abstract Friction stir welding (FSW) is becoming an essential welding technique in the aerospace industry. However, friction stir welds are usually weaker than the parent material. The dissipated heat causes a softening of the 7XXX series aluminium alloys. Post-welding heat treatments are used to restore the highest strength after welding. The reference treatment is composed of two-steps heating: a solution heat treatment typically at 470 °C for 30 min, quench in water followed by artificial aging 120 °C for 24 h. These treatments are responsible for very significant grain coarsening in the weld nugget zone known as secondary recrystallization, sometimes leading to abnormal grain growth (AGG). This is particularly true for thick plates. This secondary recrystallization phenomenon is detrimental for tensile performances. A detailed analysis of the conditions leading to secondary recrystallization during post-welding heat treatments is provided. A procedure to avoid secondary recrystallization in FSWed joints is then highlighted. Thermal cycles during welding are controlled by welding on a low thermal conductivity backing plate (i.e. stainless steel) which avoids very fine grains in the bottom of the weld nugget. This new procedure opens the path to excellent welds presenting at least the strength and ductility of the T6 base material.

Microstructural and fatigue crack growth behavior inhomogeneity of trace Sc added 7085 alloy friction stir welded joint

AbstractThe inhomogeneity of friction stir weld (FSW) joint of a 7085 Al‐based alloy containing trace Sc was investigated by comparing the hardening phase morphology, grain structure, mechanical properties, and fatigue crack growth (FCG) behavior in based metal (BM), heat‐affected zone (HAZ), and weld nugget zone (WNZ). The results showed that microstructural evolution during FSW was remarkably affected by Sc addition. The recrystallization and growth of grains in BM and HAZ were restrained by coherent Al3(Sc,Zr) particles. In HAZ, partially dissolution and slight growth of precipitates resulted in softening but contributed to enhance the FCG resistance according to shear mechanism. In WNZ, high frictional heating and intense plastic deformation induced recrystallization and supersaturated solid solution which decomposed to form new reprecipitates, including many new GPII zones, η′ phases, and some coarse η equilibrium phases attached to grown incoherent Al3(Sc,Zr). Owing to combined influences of fine random orientated grain structure and reprecipitates, WNZ possessed the best fatigue endurance.

Weldability and mechanical properties of AA5083-H112 aluminum alloy and pure copper dissimilar friction spot extrusion welding-brazing

The friction spot extrusion welding-brazing (FSEW-B) process was employed to join AA5083-H112 aluminum alloy and pure Cu via the use of a Zn interlayer to improve the mechanical properties of the dissimilar joint. The attained data indicated that not only FSEW-B led to the elimination of the keyhole, which is an intrinsic flaw of the Friction Stir Spot Welding (FSSW) process, but also the results showed that adding Zn interlayer was propitious to make less brittle intermetallic compounds (IMCs) like Al4Cu9 at the Cu/Al interface. More importantly, tensile shear results demonstrated an improvement in the strength and ductility of the FSEW-B weld sample (reached 156.2 MPa), which is attributable to the lack of keyhole defect and brittle IMCs in the joint.