Optimization of surface roughness,cutting force and tool wear of nitrogen alloyed duplex stainless steel in a dry turning process using Taguchi method

In this work, the dry turning parameters of two different grades of nitrogen alloyed duplex stainless steel are optimized by using Taguchi method. The turning operations were carried out with TiC and TiCN coated carbide cutting tool inserts. The experiments were conducted at three different cutting speeds (80, 100 and 120 m/min) with three different feed rates (0.04, 0.08 and 0.12 mm/rev) and a constant depth of cut (0.5 mm). The cutting parameters are optimized using signal to noise ratio and the analysis of variance. The effects of cutting speed and feed rate on surface roughness, cutting force and tool wear were analyzed. The results revealed that the feed rate is the more significant parameter influencing the surface roughness and cutting force. The cutting speed was identified as the more significant parameter influencing the tool wear. Tool wear was analyzed using scanning electron microscope image. The confirmation tests are carried out at optimum cutting conditions. The results at optimum cutting condition are predicted using estimated signal to noise ratio equation. The predicted results are found to be closer to experimental results within 8% deviations.     

Optimization of surface roughness and flank wear using the Taguchi method in milling of Hadfield steel with PVD and CVD coated inserts

In this paper, the Taguchi method and regression analysis have been applied to evaluate the machinability of Hadfield steel with PVD TiAlN- and CVD TiCN/Al₂O₃-coated carbide inserts under dry milling conditions. Several experiments were conducted using the L₁₈ (2 × 3 × 3) full-factorial design with a mixed orthogonal array on a CNC vertical machining center. Analysis of variance (ANOVA) was used to determine the effects of the machining parameters on surface roughness and flank wear. The cutting tool, cutting speed and feed rate were selected as machining parameters. The analysis results revealed that the feed rate was the dominant factor affecting surface roughness and cutting speed was the dominant factor affecting flank wear. Linear and quadratic regression analyses were applied to predict the outcomes of the experiment. The predicted values and measured values were very close to each other. Confirmation test results showed that the Taguchi method was very successful in the optimization of machining parameters for minimum surface roughness and flank wear in the milling the Hadfield steel.     

Sliding/rolling wear performance of plasma nitrided H11 hot working steel

H11 steel discs were tested by considering sliding/rolling friction under dry and lubricated conditions. The H11 discs were plasma nitrided at 500 °C and 550 °C for 9 h. Wear tests were conducted at different slip ratios of 1.79%, 10.53% and 22.22%. The test loads were 100 N, 150 N and 200 N. It was determined that plasma-nitrided H11 discs had a surface hardness of 1200–1400 HV0.1. Plasma nitriding produced wear performance much higher than those of the un-nitrided but hardened samples. The wear mechanism of the plasma-nitrided discs was a mixture of adhesive wear, abrasive wear and plastic yielding.     

Effect of SiC particles on the friction and wear behavior of Ti3Si(Al)C2-based composites

The non-lubricated, sliding friction and wear behavior of Ti₃Si(Al)C₂ and SiC-reinforced Ti₃Si(Al)C₂ composites against AISI 52100 bearing steel ball were investigated using a ball-on-flat, reciprocating tribometer at room temperature. The contact load was varied from 5 to 20 N. For monolithic Ti₃Si(Al)C₂, high friction coefficients between 0.61 and 0.90 and wear rates between 1.79 × 10⁻³ and 2.68 × 10⁻³ mm³ (N m)⁻¹ were measured. With increasing SiC content in the composites, both the friction coefficients and the wear rates were significantly decreased. The friction coefficients reduced to a value between 0.38 and 0.50, and the wear rates to between 2.64 × 10⁻⁴ and 1.93 × 10⁻⁵ mm³ (N m)⁻¹ when the SiC content ranged from 10 to 30 vol.%. The enhanced wear resistance of Ti₃Si(Al)C₂ is mainly attributed to the facts that the hard SiC particles inhibit the plastic deformation and fracture of the soft matrix, the oxide debris lubricate the counterpair, and the wear mode converts from adhesive wear to abrasive wear during dry sliding.     

Electrical discharge machining of the AISI D6 tool steel: Prediction and modeling of the material removal rate and tool wear ratio

In this investigation, response surface method was used to predict and optimize the material removal rate and tool wear ratio during electrical discharge machining of AISI D6 tool steel. Pulse on time, pulse current, and voltage were considered as input process parameters. Furthermore, the analysis of variance was employed for checking the developed model results. The results revealed that higher values of pulse on time resulted in higher values of material removal rate and lower amounts of tool wear ratio. In addition, increasing the pulse current caused to higher amounts of both material removal rate and tool wear ratio. Moreover, the higher the input voltage, the lower the both material removal rate and tool wear ratio. The optimal condition to obtain a maximum of material removal rate and a minimum of tool wear rate was 40 μs, 14 A and 150 V, respectively for the pulse on time, pulse current and input voltage.     

Wear mechanisms of WC coated and uncoated tools in finish turning of Inconel 718

This paper presents the results of an experimental investigation on the wear mechanisms of uncoated tungsten carbide (WC) and coated tools (single-layer (TiAlN) PVD, and triple-layer (TiCN/Al₂O₃/TiN) CVD) in oblique finish turning of Inconel 718. Tool wear rate and wear mechanisms were evaluated for cutting speeds, 50<V<100 m/min, and feed rates, 0.075<f<0.125 mm/rev, at a constant depth of cut of 0.25 mm. It was concluded that abrasive and adhesive wear were the most dominant wear mechanisms, controlling the deterioration and final failure of the WC tools. While the triple layer CVD coated tools exhibited the highest wear resistance at high cutting speeds and low feeds, uncoated tools outperformed the single and multi-layer coated tools in the low range of cutting speeds and intermediate feeds. The cutting tool with single-layer PVD coating outperformed the other tools at the medium cutting speed.     

Steel machining chips as reinforcements to improve sliding wear resistance of metal alloys: Study of a model Zn-based alloy system

Two new steel-reinforced, metal-matrix composites (MMCs), Kirksite+1080 and Kirksite+M2 are developed by adding 25 wt% of AISI 1080/AISI M2 steel machining chips to a zinc-based alloy, Kirksite (4% Al and 3% Cu). The sliding wear resistance of the Zn alloy and the two MMCs, against AISI 52100 steel, is determined under increasing normal load (1–10 N) and temperature (25–150 °C), using a pin-on-disc configuration. The MMCs are found to exhibit superior wear performance under all test conditions. At room temperature, a maximum wear reduction in excess of 70% is obtained for the composites relative to the Zn-alloy at the highest load of 10 N. This reduction is as much as 86% at 150 °C and 1 N for the Kirksite+M2. The wear-reducing ability of the steel reinforcements is generally greater at the more severe contact conditions. The stability of the MMC matrices and recommended limits to the MMC operating temperatures are established using deformation measurements made via dynamic mechanical analysis. The principal wear mechanisms are analysed based on the sliding wear measurements, complemented by optical microscopy and SEM observations, and EDX microanalysis. The results show that the steel chip reinforcements are effective in improving the wear resistance of Zn alloys under severe conditions. Implications for use of low-cost machining chips as reinforcements to create MMCs for improved wear performance, and for recycling/reuse of these chips in advanced structural material systems are discussed.     

Friction and dry sliding wear behaviour of cermets

The friction and wear behaviour of cermets/steel rubbing pairs were investigated. Friction and wear tests were carried out using three different crèmets on the base of tungsten, titanium and chromium carbides under dry sliding conditions against steel disk (0.45% C). Sliding wear tests were carried out using modified block-on-ring equipment at a sliding speed of 2.2 m/s and normal load 40 N.It is shown that wear resistance and coefficient of friction depend on the type and chemical composition of the cermets. The WC–Co cermets have the highest wear resistance. The wear rate of WC–Co and TiC–NiMo cermets increased with increasing binder content in the cermets. The wear of Cr₃C₂–Ni cermets is more complicated and depends on the composition of cermets. The wear of WC–Co cermets is caused mainly by preferential removal of the cobalt binder, followed by fracture of the intergranular boundaries and fragmentation of the carbide grains. The main wear mechanism in the TiC–NiMo cermets is polishing (micro-abrasion) and adhesion, resulting in a low wear rate. The main wear mechanism of Cr₃C₂–Ni cermets involves thermal cracking and fatigue-related crushing of large carbide grains and carbide framework and also adhesion.     

The effects of nickel and carbon concentrations on the wear resistance of Fe–Ni–C austenitic alloys

The effects of nickel and carbon concentrations on the wear resistance of Fe–xNi–yC (x = 14–20 wt.%, y = 0.6–1.0 wt.%) were investigated with respect to strain energy initiation of the martensitic transformation and hardness. The strain energy needed to initiate the martensitic transformation increased with increasing carbon and nickel concentrations, except in 1.0 wt.% C alloys. The wear resistance of the material decreased with increasing carbon concentration up to 0.9 wt.% C. This effect is most likely due to decrement of the martensite volume fraction with increasing carbon concentration induced by the incremental strain energy required to begin the martensitic transformation. In the case of 1.0 wt.% C, the improved wear resistance may be due to carbide precipitation.     

The evaluation of the effects of control factors on surface roughness in the drilling of Waspaloy superalloy

In this study, the effects of cutting tool type (Ct), cutting speed (Vc), feed rate (f) and drill bit angle (A) on the average surface roughness (Ra) were investigated in the drilling of Waspaloy superalloy with coated and uncoated solid carbide drills. Experimental studies were performed in the orthogonal array of L18 (2¹ × 3³) by using Taguchi method. A second order predictive equation was developed with Linear Regression Analysis and coefficient of correlation for Ra calculated as R² = 96.9%. The most effective parameters on Ra were determined as A, f, Vc and Ct with 49.44%, 15.0%, 14.45% and 13.47% contribution ratios, respectively. Ra surface roughness values increased with the increasing tool wear. In this study, the chip formation and tool wear were also evaluated. Three types chip formation such as spiral chip, string chip and short chip were observed in the drilling of Waspaloy with solid carbide drills.     

Tribo-oxidation maps for Ti against steel

A fundamental study of wear transition regimes was carried out for a pin-on-disk sliding couple, involving titanium and steel. The sliding speed was varied from 0.38 to 1.5 m s⁻¹ and the normal load from 10 to 50 N. Wear mapping approaches have been undertaken to represent the transitions in wear modes and wear mechanisms regimes, as a function of applied normal loads and sliding speeds and for both pin and disc separately on the basis of experimental results. Dry sliding wear behaviour of steel was characterized by tribo-oxidative wear with high material transfer from the titanium. In contrast, adhesive wear was more prevalent for the titanium and oxidative wear mechanisms led to formation of non-protective films on the surface.     

Wear behaviour of iron boride coatings produced by VPS technique on carbon steels

The vacuum plasma spray (VPS) technique is a useful tool for designing the characteristics of the coatings and, thus, the tribological properties of coated components. In the present paper, the wear properties of iron boride coatings produced by means of VPS technique on AISI 1040 steel samples were evaluated as a function of their microstructural characteristics. One coating type was obtained by using Fe₂B pure powder, the other with differentiated FeB + α-Fe blends, with the FeB content increasing and α-Fe content decreasing from the matrix to the surface. Wear tests were performed by means of a tribometer in block-on-ring configuration, without lubricant and in air, by using 40- and 60-N coupling loads and 0.8- and 1.6-m s⁻¹ sliding velocities. On Fe₂B coated samples, wear is essentially oxidative until the failure of the coating, the fragments of which cause a third body abrasion. On the FeB + α-Fe coated samples the wear mechanism is mainly oxidative and the coating totally wears out without spalling as a consequence of its graded structure, which succeeds in both improving the adhesion of the coating to the substrate and reducing the residual stress at the coating–substrate interface.     

Wear behavior of Cu–La2O3 composite with or without electrical current

A new type Cu–La₂O₃ composite was fabricated by internal oxidation method using powder metallurgy. Sliding wear behavior of the Cu–La₂O₃ composites was studied by using a pin-on-disk wear tester under dry sliding conditions with or without electrical current, rubbing against GCr15 type bearing steel disk at a constant sliding speed of 20 m/s. The influence of varying applied load and electrical current was investigated. The worn surfaces were examined using scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) to determine the wear mechanisms. The results showed the Cu–La₂O₃ composites had an electrical conductivity of 81.9% IACS (International Annealed Copper Standard, 100% IACS = 58 MS/m) and a hardness of HV105. The wear rate of the Cu–La₂O₃ composite pins increased with the increase in the electrical current at high sliding speed. The main wear mechanisms of the Cu–La₂O₃ composites were found to be adhesive wear, abrasive wear and arc erosion.     

Mechanical and unlubricated tribological properties of titanium-containing diamond-like carbon coatings

Titanium-containing diamond-like carbon (Ti-DLC) coatings were deposited on steel with a close-field unbalanced magnetron sputtering in a mixed argon/acetylene atmosphere. The morphology and structure of Ti-DLC coatings were investigated by scanning electron microscopy, transmission electron microscopy, atomic force microscopy and Raman spectroscopy. Nanoindentation, nanoscratch and unlubricated wear tests were carried out to evaluate the hardness, adhesive and tribological properties of Ti-DLC coatings. Electron microscopic observations demonstrated the presence of titanium-rich nanoscale regions surrounded by amorphous carbon structures in Ti-DLC coating. The Ti-DLC coatings exhibit friction coefficients of 0.12–0.25 and wear rates of 1.82 × 10^?9 to 4.29 × 10^?8 mm³/Nm, depending on the counterfaces, sliding speed and temperature. The Ti-DLC/alumina tribo-pair shows a lower friction coefficient than the Ti-DLC/steel tribo-pair under the identical wear conditions. Increasing the test temperature from room temperature to 200 °C reduces the coefficient of friction and, however, clearly increases the wear rate of Ti-DLC coatings. Different wear mechanisms, such as surface polishing, delamination and tribo-chemical reactions, were found in the tribo-contact areas, depending on different wear conditions.     

Wear mechanism of coated tools in the turning of ductile cast iron having wide range of tensile strength

In this study different specimens of ductile cast iron with tensile strength ranking from 400 MPa to 675 MPa were turned with K15 carbide, TiN coated and TiAlN coated tool in order to investigate wear mechanism and performance. Cutting forces and cutting temperature were similar for both coated tools, however flank wear and BUE were the lowest on the TiAlN coated tool, for this reason the TiAlN coated tool is suitable in the machining of ductile cast iron. The proposed tool wear mechanism is based on like-intermittent cutting caused by the pass from hard matrix to the soft graphite occasioning wear by adhesion. The analysis of the flank wear on coated tools is proposed by means of the wear curves in logarithmic scale instead of the usual linear scale. In this way, the change in wear rate is easily observed. This phenomenon was related with the wear out of the coating layer. The partial loss of the coating layer on cutting edge was confirmed by the EDS mapping images and SEM photographs.     

Plastic deformation of 25CrMo4 steel during wear: Effect of the temperature,the normal force,the sliding velocity and the structural state

This article follows a previous study on friction and wear of 25CrMo4 steel [N. Khanafi-Benghalem, K. Loucif, E. Felder, F. Delamare, Influence de la température sur les mécanismes de frottement et d’usure des aciers X12NiCrMoSi25-20 et 25CrMo4 glissant sur du carbure de tungstène, Matériaux et techniques 93 (2005) 347–362]. The aim of our work is to study in more details the process of plastic deformation and the wear rate of this steel in lubricated sliding against cemented tungsten carbide, process observed in the previous work. The considered parameters are the temperature T (from 20 to 200 °C), the normal force P (from 500 to 1500 N), the steel structure (normalised HV 220 and quenched/tempered HV 480 states) and the sliding velocity v (from 0.05 to 0.3 m/s). We measured the friction coefficient and the sample total volume loss. A displacement sensor follows the volume loss evolution during the test; this follow-up is approximate because of the sample plastic flow which leads to the formation of peripheral burrs. All the tests conditions generate a significant plastic deformation of the sample steel, even in the quenched/tempered state: it produces a marked increase of the surface hardness, the work hardened layer being much finer for the quenched/tempered state (15 μm) than for the normalised state (40 μm at 20 °C). For temperatures T ≤ 100 °C in normalised state, the wear follows the Archard's law with an increasing rate with temperature. For T ≥ 120 °C, the wear rate decreases during the test, the global volume of wear being a decreasing function of T. For the quenched/tempered state, the wear rate decreases with the increase of the normal force, this decrease is less than 30% of the normalised state value. The material heating during the wear tests is well correlated with the friction dissipated power, but remains small, except in extreme cases (v maximum, great friction at high temperatures). These results suggest the existence of two wear mechanisms: abrasion by sample debris and burrs emission by plastic flow. The abrasion is probably the dominating mechanism for the tests carried out at the lowest temperatures. The plastic flow becomes a significant component at the highest temperatures. Using a contact model, we discuss to what extent the influence of the temperature and the strain rate on the steel hardness and ductility could explain the temperature and the sliding velocity effect on wear. Other phenomena are probably present: the influence of the steel microstructure and the lubricant on the size and/or the number of particles responsible for abrasion.     

The effect of oil mist supply on cutting point temperature and tool wear in driven rotary cutting

We examined cutting point temperature and tool wear in driven rotary cutting. Cutting tests under dry and minimum-quantity-lubrication (MQL) conditions of stainless steel (SUS304) were carried out. Cutting point temperature was measured using a tool-work-thermocouple method at various cutting speeds. Cutting point temperature tends to increase with increased cutting speed. In driven rotary cutting, cutting point temperature was lower than that of non-rotation cutting. At high-speed cutting of 500 m/min, cutting point temperature was over 1200 °C in the non-rotation tool, but 1000 °C with driven rotary cutting. In addition, when driven rotary cutting was used with MQL, cutting point temperature was decreased to 900 °C. The magnitude of tool wear corresponded almost precisely to cutting point temperature. Severe adhesion on the rake face was observed and resulted in progressive wear on the rake face in rotary cutting at a cutting speed of 100 m/min. The appropriate cutting speed range passively shifts higher from the viewpoint of cutting temperature with rotary cutting.     

Tribological behaviour of carbide-free bainitic steel under dry rolling/sliding conditions

The dry rolling/sliding wear behaviour of Si alloyed carbide free bainitic steel austempered at different temperatures and sliding distances has been evaluated. 60SiCr7 spring steel samples were austempered in a salt bath maintained at 250, 300 and 350 °C respectively for 1 h. Rolling with 5% sliding wear tests were performed using self mated discs for three different test cycles, namely 6000, 18,000 and 30,000 cycles. The aim was to study the wear performance of the 60SiCr7 steel with a carbide-free microstructure containing different amounts of retained austenite. An in-depth microstructural characterization has been carried out before and after the wear tests in order to link the wear behaviour to the microstructure of each sample. The wear resistance has been expressed by means of the specific wear calculated from the mass loss after the tests. The worn surfaces were analysed by scanning electron microscopy and X-ray diffraction. Microhardness profiles were also obtained in order to analyse strain-hardening effects beneath the contact surfaces. The results indicate that the material with highest hardness—the one austempered at 250 °C—exhibited the lowest wear rate in every case. It was also observed that the hardness increment and thickness of the hardened layer increases with increasing the austempering temperature and number of test cycles. Finally, the results appear to indicate that the initial roughness of the samples has no major effect in the wear rate of the samples above 2500 cycles. The higher wear performance of the sample austempered at 250 °C has been attributed to its superior mechanical properties provided by its finer microstructure. It has been evidenced that all samples undergo the TRIP phenomenon since, after wear; no retained austenite could be detected by XRD.     

Effect of electrical current on tribological behavior of copper-impregnated metallized carbon against a Cu–Cr–Zr alloy

A block-on-slip ring-type wear tester was used to investigate the tribological behavior of copper-impregnated metallized carbon against a Cu–Cr–Zr alloy under 2 to 6 N applied load and 0 to 20 A electrical current. The sliding speed was maintained at 25 km/h. The wear loss of copper-impregnated metallized carbon increased with greater electrical current. Under a certain applied load, the wear loss with electrical current was minimized. The tribo-layer had an apparent effect on the friction coefficient. The wear mechanisms were complex, consisting of adhesive wear, abrasive wear and arc erosion.     

Effect of tool pin design on the microstructural evolutions and tribological characteristics of friction stir processed structural steel

In this research, friction stir processing (FSP) technique is applied for the surface modification of ST14 structural steel. Tungsten carbide tools with cylindrical, conical, square and triangular pin designs are used for surface modification at rotational speed of 400 rpm, normal force of 5 KN and traverse speed of 100 mm min⁻¹. Mechanical and tribological properties of the processed surfaces including microhardness and wear characteristics are studied in detail. Furthermore, microstructural evolutions and worn surfaces are investigated by optical and scanning electron microscopes. Based on the achievements, all designed pins were successfully applicable for low carbon steel to produce defect-free processed material. By the microstructural changes within the stirred zone, the processed specimen is obtained higher mechanical properties. This is due to the formation of fine grains as the consequence of imposing intensive plastic deformation during FSP; however, this issue is highlighted by using square pin design. In this case, minimum grain size of 5 μm and maximum hardness of 320 VHN, as well as, maximum wear resistance are all examined for the specimen modified by square pin.