**2. Experimental details**

Standardised experimental tests are carried out on high-speed micromachine setup as shown in **Figure 1**. The work material considered was Ti-6Al-4V ELI titanium alloy (Grade 23) of dimensions 60 × 40 × 4 mm as shown in **Figure 2**. Chemical composition and properties of the work material are shown in **Tables 1** and **2**. Experimental tests conducted are shown in **Table 3**. Two flute uncoated tungsten

**127**

**Table 2.**

*The Comparison of Cutting Tools for High Speed Machining of Ti-6Al-4V ELI Alloy (Grade 23)*

**Properties Metric** Tensile strength 860 MPa Yield strength 790 MPa Poisson's ratio 0.342 Elastic modulus 113.8 GPa Shear modulus 44.0 GPa Elongation at break 15% Hardness Rockwell 35 Density 4.43 g/cm3 Melting point 1604–1660°C

*Mechanical and physical properties of Ti-6Al-4V ELI titanium alloy (Grade 23).*

*Chemical composition of Ti-6Al-4V ELI titanium alloy (Grade 23).*

**Element wt%** Titanium, Ti 88.09–91 Aluminium, Al 5.5–6.5 Vanadium, V 3.5–4.5 Iron, Fe ≤0.25 Carbon, C ≤0.080 Nitrogen, N ≤0.030 Hydrogen, H ≤0.0125 Other ≤0.50 Total 100

carbide end mills and physical vapour deposition-coated TiAlN and AlTiN tungsten carbide end mills of diameter 500 μm supplied by IND-SPHINX Axis tools were used in this work as shown in **Figure 3**. The total length of each machined slot was 12 mm. Tool over hang length considered was 18 mm. The width of cut is 500 μm as the process is slot milling operation. Cutting edge radius of tool identified is 2.71 μm through SEM. Coating of the material as specified by the IND-SPHINX Axis tools is

*DOI: http://dx.doi.org/10.5772/intechopen.80641*

*Ti-6Al-4V ELI titanium alloy (Grade 23).*

**Figure 2.**

**Table 1.**

**Figure 1.** *High speed micromachine.*

*The Comparison of Cutting Tools for High Speed Machining of Ti-6Al-4V ELI Alloy (Grade 23) DOI: http://dx.doi.org/10.5772/intechopen.80641*

#### **Figure 2.**

*Titanium Alloys - Novel Aspects of Their Manufacturing and Processing*

pressure when machining titanium alloys.

breakability which results in improved tool life. Increase in the pressure of coolant supply also improves tool life. Notch wear was reduced by increasing coolant supply

Hassanpour et al. [32] investigated the cutting force, microhardness, surface roughness and burr size in micromilling of Ti-6Al-4V using minimum quantity lubrication. They found that cutting speed and feed per tooth significantly affect the surface roughness. Bandapalli et al. [33] have investigated the influence of machining parameters in high-speed micro-end milling of commercially pure titanium Grade 2 and found that cutting forces and surface roughness formation increases at high spindle speed by increasing feed rate and depth of cut. Ghani et al. [34] investigated the wear mechanism of uncoated carbide cutting tool in milling of aluminium metal matrix composite (AlSi/AlN MMC), PVD-coated TiAlN/AlCrN tool in milling of Inconel 718 and uncoated tool in turning of Ti-6Al-4V ELI. They found that tools failed primarily on two main areas of the flank and rake faces for cutting the Inconel 718 and titanium alloy. Wear such as crater, nose wear, abrasion, notching, fracturing and cracking were observed. In machining AlSi/AlN MMC, the tools mainly failed due to the uniform flank wear that was caused by abrasion.

However, research findings related to considered machining parameters in highspeed micro-end milling (HSMEM) of titanium alloys for comparison and evaluation of uncoated, PVD-coated TiAlN and AlTiN tools are inadequate. The purpose of this research work is to evaluate the performance of tools like uncoated and physical vapour deposition (PVD)-coated TiAlN and AlTiN tools in terms of tool wear formation in HSMEM of alpha + beta Ti-6Al-4V ELI titanium alloy (Grade 23). The goal was to improve the quality or productivity of the specific machining process based on empirical experiments using a variety of speeds, feeds and depth of cut. This work is categorised into four sections, first with an introduction. Experimental

details were discussed in Section 2. Results and discussion were presented in

Standardised experimental tests are carried out on high-speed micromachine setup as shown in **Figure 1**. The work material considered was Ti-6Al-4V ELI titanium alloy (Grade 23) of dimensions 60 × 40 × 4 mm as shown in **Figure 2**. Chemical

composition and properties of the work material are shown in **Tables 1** and **2**. Experimental tests conducted are shown in **Table 3**. Two flute uncoated tungsten

Sections 3 and 4 and finally Section 5 is presented with conclusions.

**2. Experimental details**

**126**

**Figure 1.**

*High speed micromachine.*

*Ti-6Al-4V ELI titanium alloy (Grade 23).*


#### **Table 1.**

*Mechanical and physical properties of Ti-6Al-4V ELI titanium alloy (Grade 23).*


#### **Table 2.**

*Chemical composition of Ti-6Al-4V ELI titanium alloy (Grade 23).*

carbide end mills and physical vapour deposition-coated TiAlN and AlTiN tungsten carbide end mills of diameter 500 μm supplied by IND-SPHINX Axis tools were used in this work as shown in **Figure 3**. The total length of each machined slot was 12 mm. Tool over hang length considered was 18 mm. The width of cut is 500 μm as the process is slot milling operation. Cutting edge radius of tool identified is 2.71 μm through SEM. Coating of the material as specified by the IND-SPHINX Axis tools is


#### *Titanium Alloys - Novel Aspects of Their Manufacturing and Processing*

#### **Table 3.**

*Resultant cutting forces for uncoated, coated TiAlN and AlTiN WC tools.*

**129**

*The Comparison of Cutting Tools for High Speed Machining of Ti-6Al-4V ELI Alloy (Grade 23)*

2–6 μm. Rake angle of the tool is +5°. Static run-out of the tool was measured as 3 μm. No structural vibrations were observed under considered machining conditions. Chip thickness observed is about 3 μm. Machining time was 10–12 s for 30,000 rpm,

 = 27 total runs were conducted for determining the effect of the process parameters on the cutting force and tool wear. Three levels of tool rotation speed—30,000, 70,000 and 110,000 rpm, that is, cutting velocity of 47, 110 and 173 m/min, three levels of feed rate—2, 5 and 8 μm/tooth and three levels of depth of cut—0.02, 0.06 and 0.1 mm were selected in these experiments. Two sets of experimentation, that is, one original and one repetition were performed in which total number of machined slots are—162 (27 × 2 × 3 tool types). Six uncoated tools for 54 experiments, 6 TiAlN tools for 54 experiments and 6 AlTiN tools for 54 experiments were used in this experimentation. End mill was changed with new one after machining nine slots on the workpiece for verification and observation of cutting forces and tool wear. Coated tools were selected because they provide high wear resistance, withstand mechanical and thermal shock, plastic deformation, act as barrier towards wear formation, reduce subsurface defects on workpiece by generating less heat, high hot hardness, chemical inertness to reduce development of built-up edge and occurrence of coating delamination, less burr formation and ability to withstand high cutting forces. In accordance with the above view, uncoated and PVD-coated TiAlN and AlTiN tungsten carbide end mills were considered in the present research work. Tool wear was examined using HITACHI-S3400N scanning electron microscope (SEM)

Micro-end milling is one of the most commonly used machining processes and has more complex geometry due to its rotating tool, multiple cutting edges and intermittent cutting action. Cutting forces are the main cause of the deformations of machine tool structures and workpieces resulting in form errors and tolerance violations. Although they may affect the structural components of a machine tool distributed in a large space, cutting forces are generated in a very small area at the work-tool interface. A cutting origin was set through a CCD camera because the tool diameter was extremely small and direct origin setting with naked eye was difficult and could result in significant errors. Cutting forces in three directions Fx, Fy and Fz measured using tool dynamometer, and from the signal analyser, the forces were interpreted in the computer. Resultant cutting forces were calculated by Eq.

(1). Experimental results of resultant cutting forces are shown in **Table 3**.

Fx <sup>2</sup> + Fy

At 30,000 rpm, if depth of cut and feed is varied, then resultant cutting force increased by 63% as shown in **Figure 4(a)**. At 70,000 rpm, if depth of cut and feed is varied, then resultant cutting force increased by 87% as shown in **Figure 4(b)**. At 110,000 rpm, if depth of cut and feed is varied, then resultant cutting force

\_\_\_\_\_\_\_\_\_\_\_

<sup>2</sup> + Fz

<sup>2</sup> (1)

= 3 factors, each with three levels,

*DOI: http://dx.doi.org/10.5772/intechopen.80641*

33

6–8 s for 70,000 rpm and 3–5 s for 110,000 rpm. Parametric experiments, full factorial design 33

equipped with energy dispersive spectroscope (EDS).

**3. Results and discussion**

FR = √

increases by 83% as shown in **Figure 4(c)**.

*3.1.1 Micromilling with uncoated tools*

**3.1 Cutting force analysis**

**Figure 3.** *Micro-end mills.*

*The Comparison of Cutting Tools for High Speed Machining of Ti-6Al-4V ELI Alloy (Grade 23) DOI: http://dx.doi.org/10.5772/intechopen.80641*

2–6 μm. Rake angle of the tool is +5°. Static run-out of the tool was measured as 3 μm. No structural vibrations were observed under considered machining conditions. Chip thickness observed is about 3 μm. Machining time was 10–12 s for 30,000 rpm, 6–8 s for 70,000 rpm and 3–5 s for 110,000 rpm.

Parametric experiments, full factorial design 33 = 3 factors, each with three levels, 33 = 27 total runs were conducted for determining the effect of the process parameters on the cutting force and tool wear. Three levels of tool rotation speed—30,000, 70,000 and 110,000 rpm, that is, cutting velocity of 47, 110 and 173 m/min, three levels of feed rate—2, 5 and 8 μm/tooth and three levels of depth of cut—0.02, 0.06 and 0.1 mm were selected in these experiments. Two sets of experimentation, that is, one original and one repetition were performed in which total number of machined slots are—162 (27 × 2 × 3 tool types). Six uncoated tools for 54 experiments, 6 TiAlN tools for 54 experiments and 6 AlTiN tools for 54 experiments were used in this experimentation. End mill was changed with new one after machining nine slots on the workpiece for verification and observation of cutting forces and tool wear. Coated tools were selected because they provide high wear resistance, withstand mechanical and thermal shock, plastic deformation, act as barrier towards wear formation, reduce subsurface defects on workpiece by generating less heat, high hot hardness, chemical inertness to reduce development of built-up edge and occurrence of coating delamination, less burr formation and ability to withstand high cutting forces. In accordance with the above view, uncoated and PVD-coated TiAlN and AlTiN tungsten carbide end mills were considered in the present research work. Tool wear was examined using HITACHI-S3400N scanning electron microscope (SEM) equipped with energy dispersive spectroscope (EDS).

### **3. Results and discussion**

*Titanium Alloys - Novel Aspects of Their Manufacturing and Processing*

*Resultant cutting forces for uncoated, coated TiAlN and AlTiN WC tools.*

**Feed (μm/ tooth)**

**Depth of cut (mm)**

 30,000 2 0.02 0.37 0.34 0.33 30,000 5 0.02 0.39 0.34 0.31 30,000 8 0.02 0.41 0.36 0.34 30,000 2 0.06 0.46 0.63 0.62 30,000 5 0.06 0.57 0.68 0.67 30,000 8 0.06 0.69 0.81 0.66 30,000 2 0.1 0.75 0.76 1.5 30,000 5 0.1 0.82 0.88 1.55 30,000 8 0.1 1.01 1.16 1.56 70,000 2 0.02 0.09 0.14 0.13 70,000 5 0.02 0.21 0.21 0.21 70,000 8 0.02 0.37 0.29 0.29 70,000 2 0.06 0.15 0.26 0.22 70,000 5 0.06 0.31 0.31 0.38 70,000 8 0.06 0.47 0.40 0.41 70,000 2 0.1 0.21 0.35 0.57 70,000 5 0.1 0.43 0.46 0.54 70,000 8 0.1 0.56 0.58 0.63 110,000 2 0.02 0.12 0.13 0.22 110,000 5 0.02 0.31 0.28 0.28 110,000 8 0.02 0.49 0.34 0.28 110,000 2 0.06 0.16 0.15 0.19 110,000 5 0.06 0.37 0.27 0.36 110,000 8 0.06 0.56 0.37 0.37 110,000 2 0.1 0.18 0.16 0.25 110,000 5 0.1 0.46 0.34 0.61 110,000 8 0.1 0.67 0.41 0.77

**Cutting force (N) Uncoated TiAlN AlTiN**

**Spindle speed (rpm)**

**Exp. no**

**128**

**Figure 3.** *Micro-end mills.*

**Table 3.**

### **3.1 Cutting force analysis**

Micro-end milling is one of the most commonly used machining processes and has more complex geometry due to its rotating tool, multiple cutting edges and intermittent cutting action. Cutting forces are the main cause of the deformations of machine tool structures and workpieces resulting in form errors and tolerance violations. Although they may affect the structural components of a machine tool distributed in a large space, cutting forces are generated in a very small area at the work-tool interface. A cutting origin was set through a CCD camera because the tool diameter was extremely small and direct origin setting with naked eye was difficult and could result in significant errors. Cutting forces in three directions Fx, Fy and Fz measured using tool dynamometer, and from the signal analyser, the forces were interpreted in the computer. Resultant cutting forces were calculated by Eq. (1). Experimental results of resultant cutting forces are shown in **Table 3**.

$$\mathbf{F\_R} = \sqrt{\mathbf{F\_x}^2 + \mathbf{F\_y}^2 + \mathbf{F\_z}^2} \tag{1}$$

#### *3.1.1 Micromilling with uncoated tools*

At 30,000 rpm, if depth of cut and feed is varied, then resultant cutting force increased by 63% as shown in **Figure 4(a)**. At 70,000 rpm, if depth of cut and feed is varied, then resultant cutting force increased by 87% as shown in **Figure 4(b)**. At 110,000 rpm, if depth of cut and feed is varied, then resultant cutting force increases by 83% as shown in **Figure 4(c)**.

### *3.1.2 Micromilling with TiAlN tools*

At 30,000 rpm, if depth of cut and feed is varied, then resultant cutting force increases by 81.7% as shown in **Figure 4(a)**. At 70,000 rpm, if depth of cut and feed is varied, then resultant cutting force increases by 85.14% as shown in **Figure 4(b)**. At 110,000 rpm, if depth of cut and feed is varied, then resultant cutting force increases by 78% as shown in **Figure 4(c)**.

#### *3.1.3 Micromilling with AlTiN tools*

At 30,000 rpm, if depth of cut and feed is varied, then resultant cutting force increases by 82.6% as shown in **Figure 4(a)**. At 70,000 rpm, if depth of cut and feed is varied, then resultant cutting force increases by 87% as shown in **Figure 4(b)**. At 110,000 rpm, if depth of cut and feed is varied, then resultant cutting force increases by 85% as shown in **Figure 4(c)**.

From the experimentation, it is observed that the resultant cutting force increase might be due to the increment in feed rate and depth of cut, leading to more chip formation, high contact between tool and chip, high-temperature formation by shearing and ploughing action reducing the yield strength of work material. It was observed that when spindle speed is increased, while the depth of cut and feed rate is kept at low, then cutting force generated was less. When depth of cut and feed rates are reduced, the chip load encountered in the process becomes the same order of magnitude as the grain size of many alloys. The cutting-edge radius of the end mill is comparable in size to the chip thickness. As a result, no chip is formed when the chip thickness is below the minimum chip thickness and instead part of the work material plastically deforms under the edge of the tool and the rest elastically recovers. This change in the chip formation process, known as minimum chip thickness effect and the associated material elastic recovery cases, increased cutting forces and surface roughness. Observed irregularity on the machined surface due to the plastic side flow and burr formation seem to suggest that the tool workpiece interaction is more likely to be elastic-plastic in nature. Due to the increment in feed rate, depth of cut and cutting speed, the tool wear and cutting-edge distortion took place that leads to more cutting force requirement to remove the material. At 30,000 rpm, uncoated tools performed better than both the coated tools. Uncoated tools produced less cutting force compared to coated tools because of tools stability and resistance to wear. At 70,000 rpm, 0.02 and 0.06 mm depth of cut with feed 2–8 μm/tooth, the uncoated tool required more cutting force to remove the material rather than both the coated tools. At 70,000 rpm, 0.1 mm depth of cut with feed 2–8 μm/tooth, the uncoated tool is found to generate less cutting force than both the coated tools. At 110,000 rpm, coated TiAlN tools are better performed than coated AlTiN and uncoated tools, which is due to increase in cutting temperature in the shear zone, thus reducing the yield strength of the workpiece material, chip thickness and tool-chip contact length. If coated TiAlN and coated AlTiN tools are compared, then performance of TiAlN tools is better. Depending on the particular parameters during machining processes, uneven phenomenon (sudden tool or spindle vibration, sudden workpiece movement) occurs, leading to increase of cutting forces. SEM and EDS analyses are performed to identify the wear and its formation mechanism on two flutes of each tool, that is, uncoated and PVD-coated AlTiN, TiAlN tungsten carbide end mills as shown in **Figures 5** and **6**. Tool wear on particular end mill is observed using SEM after machining nine slots for each set of spindle speed as shown in **Figures 7–12**. Tool wears measured on each cutting flute in two series of experiments have been considered and average values are reported as shown in **Figure 13**. Coated TiAlN tool wear was high at spindle speed

**131**

**Figure 4.**

ing conditions are shown in **Figures 7**–**12**.

*independent spindle speed (rpm), feed (μm/tooth), depth of cut (mm).*

*The Comparison of Cutting Tools for High Speed Machining of Ti-6Al-4V ELI Alloy (Grade 23)*

30,000 rpm machining conditions than uncoated and coated AlTiN tools. Uncoated tools produced less wear than both the coated tools at spindle speed 70,000 rpm machining conditions. Coated TiAlN tools produced less wear than AlTiN-coated and uncoated tools at spindle speed 110,000 rpm machining conditions. Tool wear is increased for all the tools when the feed rate and depth of cut for the considered spindle speed is increased. Adhesive wear, edge chipping, flaking, coating delamination and measured tool wear that were observed under SEM at different machin-

*Comparison of (a) uncoated, (b) coated TiAlN and (c) AlTiN WC tools for resultant cutting force (N) at* 

*DOI: http://dx.doi.org/10.5772/intechopen.80641*

*The Comparison of Cutting Tools for High Speed Machining of Ti-6Al-4V ELI Alloy (Grade 23) DOI: http://dx.doi.org/10.5772/intechopen.80641*

**Figure 4.**

*Titanium Alloys - Novel Aspects of Their Manufacturing and Processing*

At 30,000 rpm, if depth of cut and feed is varied, then resultant cutting force increases by 81.7% as shown in **Figure 4(a)**. At 70,000 rpm, if depth of cut and feed is varied, then resultant cutting force increases by 85.14% as shown in **Figure 4(b)**. At 110,000 rpm, if depth of cut and feed is varied, then resultant cutting force increases

At 30,000 rpm, if depth of cut and feed is varied, then resultant cutting force increases by 82.6% as shown in **Figure 4(a)**. At 70,000 rpm, if depth of cut and feed is varied, then resultant cutting force increases by 87% as shown in **Figure 4(b)**. At 110,000 rpm, if depth of cut and feed is varied, then resultant cutting force increases

From the experimentation, it is observed that the resultant cutting force increase might be due to the increment in feed rate and depth of cut, leading to more chip formation, high contact between tool and chip, high-temperature formation by shearing and ploughing action reducing the yield strength of work material. It was observed that when spindle speed is increased, while the depth of cut and feed rate is kept at low, then cutting force generated was less. When depth of cut and feed rates are reduced, the chip load encountered in the process becomes the same order of magnitude as the grain size of many alloys. The cutting-edge radius of the end mill is comparable in size to the chip thickness. As a result, no chip is formed when the chip thickness is below the minimum chip thickness and instead part of the work material plastically deforms under the edge of the tool and the rest elastically recovers. This change in the chip formation process, known as minimum chip thickness effect and the associated material elastic recovery cases, increased cutting forces and surface roughness. Observed irregularity on the machined surface due to the plastic side flow and burr formation seem to suggest that the tool workpiece interaction is more likely to be elastic-plastic in nature. Due to the increment in feed rate, depth of cut and cutting speed, the tool wear and cutting-edge distortion took place that leads to more cutting force requirement to remove the material. At 30,000 rpm, uncoated tools performed better than both the coated tools. Uncoated tools produced less cutting force compared to coated tools because of tools stability and resistance to wear. At 70,000 rpm, 0.02 and 0.06 mm depth of cut with feed 2–8 μm/tooth, the uncoated tool required more cutting force to remove the material rather than both the coated tools. At 70,000 rpm, 0.1 mm depth of cut with feed 2–8 μm/tooth, the uncoated tool is found to generate less cutting force than both the coated tools. At 110,000 rpm, coated TiAlN tools are better performed than coated AlTiN and uncoated tools, which is due to increase in cutting temperature in the shear zone, thus reducing the yield strength of the workpiece material, chip thickness and tool-chip contact length. If coated TiAlN and coated AlTiN tools are compared, then performance of TiAlN tools is better. Depending on the particular parameters during machining processes, uneven phenomenon (sudden tool or spindle vibration, sudden workpiece movement) occurs, leading to increase of cutting forces. SEM and EDS analyses are performed to identify the wear and its formation mechanism on two flutes of each tool, that is, uncoated and PVD-coated AlTiN, TiAlN tungsten carbide end mills as shown in **Figures 5** and **6**. Tool wear on particular end mill is observed using SEM after machining nine slots for each set of spindle speed as shown in **Figures 7–12**. Tool wears measured on each cutting flute in two series of experiments have been considered and average values are reported as shown in **Figure 13**. Coated TiAlN tool wear was high at spindle speed

*3.1.2 Micromilling with TiAlN tools*

by 78% as shown in **Figure 4(c)**.

*3.1.3 Micromilling with AlTiN tools*

by 85% as shown in **Figure 4(c)**.

**130**

*Comparison of (a) uncoated, (b) coated TiAlN and (c) AlTiN WC tools for resultant cutting force (N) at independent spindle speed (rpm), feed (μm/tooth), depth of cut (mm).*

30,000 rpm machining conditions than uncoated and coated AlTiN tools. Uncoated tools produced less wear than both the coated tools at spindle speed 70,000 rpm machining conditions. Coated TiAlN tools produced less wear than AlTiN-coated and uncoated tools at spindle speed 110,000 rpm machining conditions. Tool wear is increased for all the tools when the feed rate and depth of cut for the considered spindle speed is increased. Adhesive wear, edge chipping, flaking, coating delamination and measured tool wear that were observed under SEM at different machining conditions are shown in **Figures 7**–**12**.

#### **Figure 5.**

*SEM image of tool edge for uncoated, coated TiAlN and AlTiN WC tools with marked microzone for EDS analysis.*

**Figure 6.** *EDS spectrogram.*

**133**

**Figure 10.**

**Figure 8.**

**Figure 9.**

*Coated TiAlN tool wear at 110,000 rpm.*

*Coated AlTiN tool wear at 30,000 rpm.*

*The Comparison of Cutting Tools for High Speed Machining of Ti-6Al-4V ELI Alloy (Grade 23)*

*DOI: http://dx.doi.org/10.5772/intechopen.80641*

*Coated TiAlN tool wear at (a and b) 30,000 rpm and (c and d) 70,000 rpm.*

**Figure 7.** *(a–d) Tool wear observation for uncoated tools.*

*The Comparison of Cutting Tools for High Speed Machining of Ti-6Al-4V ELI Alloy (Grade 23) DOI: http://dx.doi.org/10.5772/intechopen.80641*

#### **Figure 8.**

*Titanium Alloys - Novel Aspects of Their Manufacturing and Processing*

*SEM image of tool edge for uncoated, coated TiAlN and AlTiN WC tools with marked microzone for EDS* 

**132**

**Figure 7.**

**Figure 6.** *EDS spectrogram.*

**Figure 5.**

*analysis.*

*(a–d) Tool wear observation for uncoated tools.*

*Coated TiAlN tool wear at (a and b) 30,000 rpm and (c and d) 70,000 rpm.*

#### **Figure 9.**

*Coated TiAlN tool wear at 110,000 rpm.*

**Figure 10.** *Coated AlTiN tool wear at 30,000 rpm.*

**Figure 11.** *Coated AlTiN tool wear at 70,000 rpm.*

**Figure 12.**

*Coated AlTiN tool wear at 110,000 rpm.*

## **3.2 EDS results**

The observed elemental composition on the worn surface of uncoated, coated TiAlN and AlTiN WC tools while machining the Ti-6Al-4V ELI titanium alloy (Grade 23) are shown in **Tables 4**–**6**.

SEM and EDS analysis for the considered machining operating parameters indicate the built-up edge, built-up layer and craters appearing at rake face and flank face of the cutting tool representing the adhesive, diffusion, abrasive and oxidation wear phenomenon on the tool surfaces. Wear confirmation process on the tool materials was discussed below.

#### *3.2.1. SEM observations*

SEM examination of the leading cutting edge for coated and uncoated tools indicates plastic deformation, adhesion wear, chipping and flaking as shown in **Figures 7–12**. In addition, coating delamination at the tool cutting edge and significant changes in the tool shape was observed under the SEM. Tool material reacts with titanium alloy by means of high chemical reaction, forming adhesive wear. During the tool-workpiece interaction, adhesive layers of tool material will break down that progresses to adhesion wear. The intimate contact between the tool and

**135**

**Table 5.**

**Figure 13.**

**Table 4.**

*EDS analysis results for uncoated tools.*

*EDS analysis results for coated TiAlN tools.*

*The Comparison of Cutting Tools for High Speed Machining of Ti-6Al-4V ELI Alloy (Grade 23)*

**Maximum composition of elements wt%** C 3–5.4 N 3–11.8 O 3–4.1 Al 0.2–0.7 Ti 0.3–10.2 V 0.3–1.1 Cr 0.3–0.8 Ba 2–9.8 W 70–84.5

**Maximum composition of elements wt%** C 6.8 N 9.8 O 9.4 Al 21.4 Ti 36.4 V 0.6 Cr 0.3–0.8 Ba 13.8 W 1.3

chip interface leads to the friction and high-temperature generation, stipulating the transmission of atoms from tool material losing its hardness and ultimately breakdown happens. It appears that both coated and uncoated tool materials were

*DOI: http://dx.doi.org/10.5772/intechopen.80641*

*Tool wear versus different machining conditions.*

*The Comparison of Cutting Tools for High Speed Machining of Ti-6Al-4V ELI Alloy (Grade 23) DOI: http://dx.doi.org/10.5772/intechopen.80641*

#### **Figure 13.**

*Titanium Alloys - Novel Aspects of Their Manufacturing and Processing*

**134**

**Figure 11.**

**Figure 12.**

**3.2 EDS results**

*Coated AlTiN tool wear at 70,000 rpm.*

*Coated AlTiN tool wear at 110,000 rpm.*

(Grade 23) are shown in **Tables 4**–**6**.

tool materials was discussed below.

*3.2.1. SEM observations*

The observed elemental composition on the worn surface of uncoated, coated TiAlN and AlTiN WC tools while machining the Ti-6Al-4V ELI titanium alloy

SEM and EDS analysis for the considered machining operating parameters indicate the built-up edge, built-up layer and craters appearing at rake face and flank face of the cutting tool representing the adhesive, diffusion, abrasive and oxidation wear phenomenon on the tool surfaces. Wear confirmation process on the

SEM examination of the leading cutting edge for coated and uncoated tools indicates plastic deformation, adhesion wear, chipping and flaking as shown in **Figures 7–12**. In addition, coating delamination at the tool cutting edge and significant changes in the tool shape was observed under the SEM. Tool material reacts with titanium alloy by means of high chemical reaction, forming adhesive wear. During the tool-workpiece interaction, adhesive layers of tool material will break down that progresses to adhesion wear. The intimate contact between the tool and

*Tool wear versus different machining conditions.*


#### **Table 4.**

*EDS analysis results for uncoated tools.*


#### **Table 5.**

*EDS analysis results for coated TiAlN tools.*

chip interface leads to the friction and high-temperature generation, stipulating the transmission of atoms from tool material losing its hardness and ultimately breakdown happens. It appears that both coated and uncoated tool materials were

#### *Titanium Alloys - Novel Aspects of Their Manufacturing and Processing*


#### **Table 6.**

*EDS analysis results for coated AlTiN tools.*

subjected to thermal and mechanical loads and could not be able to resist the wear during the interrupted cutting in the end milling process. The chip shape, segmented or continuous, decides the cutting temperature formation inciting to thermoplastic shear localization at the contact length, resulting in the diffusion process. The chip constituents and the rate of diffusion are controlled by cutting temperature. In the machining of titanium alloys, the machining parameters, particularly, cutting speed, influence the cutting temperature origination at the tool edge for initiating the diffusion process. The earlier researchers verified that cutting speeds generate high cutting temperature, a short contact length, a low shear angle and a high cutting pressure. Chip segmentation and tribological parameters—the physical medium—may be causing the coating delamination for both the coated tools while machining the titanium alloy. Since the thermal conductivities of the coating constituents are different, the heat flux q flows through the coating layer and penetrates the tool substrate. The reason behind the diffusion process at the tool substrate surface might be due to chemically instable Co binder elements. Adhesive surface between the coating layer and tool substrate surface was completely eliminated gradually by diffusion process as depicted in **Figures 7–12** and confirmed through EDS analysis.

#### *3.2.2 EDS analysis*

Adhesive, diffusion, abrasive and oxidation wear were the major means on the flank face. The elements observed on the cutting tool edge and workpiece indicate the diffusion process has taken place. From the EDS and SEM analyses, the existence of workpiece material constituents V, Al and Ti on the rake face wear land with built-up layer of cutting edge indicates diffusion might take place. Increasing cutting speed leads to the decrease in presence of V and Al at the tool cutting tool tip and it might be imaginable that Ti only sticks to the cutting tool edge. It has therefore been considered reasonable to suggest that the built-up layer was started through the sticking of Ti by different bonding actions, that is, directly proportional with temperature. Under very high speed cutting conditions, tool life depends directly on the formation of crater wear. Thin titanium oxide layer formation was observed on cutting edge of both the tools. In high-speed cutting conditions, cratering becomes so severe that the tool edge is weakened and eventually fracture which has been observed for the AlTiN and TiAlN tools at 110,000 rpm spindle speed, 0.1 mm depth of cut and 8 μm/tooth feed rate. At higher and lower

**137**

**4. Conclusions**

cutting speed influence the tool wear.

**Acknowledgements**

*The Comparison of Cutting Tools for High Speed Machining of Ti-6Al-4V ELI Alloy (Grade 23)*

spindle speeds, existence of cobalt (Co) was very negligible. This indicates that Co diffusion might take place from the tool material constituents allowing it to wear easily. Through the EDS analysis, the amount of carbon presence indicates its transfer from cutting tool material into the workpiece material, that is, diffusion process might be taking place. This transfer of carbon reacts with titanium forming TiC layer which is continuous at higher speeds known as chemical wear process, leading to crater formation on tool material as observed by earlier researchers. The occurrence of crater wear might be due to chip-tool contact stresses generation, depleting the C and Co from cutting tool. An adherent layer of TiC formation exists on the cutting edge due to the chemical reaction between the titanium workpiece and the cutting tool material. Formation of oxycarbides on the surface indicates the existence of oxygen. Earlier researchers suggested this existence by Auger spectroscopy Analysis. Researchers also suggested that TiC grains removal might be taking place from the cutting tool because of reduction in toughness as the diffusion process takes place. Replenishing of TiC grains on the tool surface will probably occur by obtaining C from WC grains [3, 12–17, 21–29, 32]. The presence of Mo, Ni, Br, Cr, Fe and V indicates the work material composition diffusivity to the tool tip. Sulphur (S), silicon (Si) and magnesium (Mg) act as protective layer or barrier for adhesive wear and prevent the welding and stiffening of the work material in the tool surface. Through EDS analysis, it can be predicted that coating delamination in the initial stages may be due to mechanical wear later on by chemical mechanisms.

Tool wear analysis of PVD-coated TiAlN and AlTiN and uncoated tungsten carbide tools in high-speed micro-end milling of alpha + beta Ti-6Al-4V ELI titanium alloy (Grade 23) was investigated by tool wear mechanisms formation using SEM and EDS analysis and cutting force analysis. If the spindle speed is maintained at constant rpm while increasing feed rate and depth of cut, then tool wear increases dramatically. By increasing spindle speed from 30,000 to 70,000 rpm while varying feed rate and depth of cut, then (i) tool wear remains constant for uncoated tools, (ii) tool wear increases for AlTiN-coated tools and (iii) tool wear remains constant for TiAlN-coated tools. By increasing spindle speed from 70,000 to 110,000 rpm while varying feed rate and depth of cut, then tool wear increases for all the tools. If coated TiAlN and coated AlTiN tools are compared, then TiAlN tools performed better for machining this alloy. Based on the investigations, it can be suggested that PVD-coated TiAlN tungsten carbide tools give better performance than PVDcoated AlTiN and uncoated tungsten carbide tools in HSMEM at 110,000 rpm when machining alpha + beta Ti-6Al-4V ELI titanium alloy (Grade 23). SEM and EDS analyses for the considered machining operating parameters indicate the built-up edge, built-up layer and craters appearing at rake face and flank face of the cutting edge representing the adhesive, diffusion, oxidation and abrasive wear phenomenon on the tool surfaces when machined on both titanium alloys. Based on the investigations, the tool and work material properties, feed rate, depth of cut and

The authors gratefully acknowledge the support offered by Professor Dr. Ramesh Kumar Singh, Machine Tools Lab, Mechanical Engineering Department, IIT Mumbai, Maharashtra, India, in providing all the facilities for conducting the

*DOI: http://dx.doi.org/10.5772/intechopen.80641*

*The Comparison of Cutting Tools for High Speed Machining of Ti-6Al-4V ELI Alloy (Grade 23) DOI: http://dx.doi.org/10.5772/intechopen.80641*

spindle speeds, existence of cobalt (Co) was very negligible. This indicates that Co diffusion might take place from the tool material constituents allowing it to wear easily. Through the EDS analysis, the amount of carbon presence indicates its transfer from cutting tool material into the workpiece material, that is, diffusion process might be taking place. This transfer of carbon reacts with titanium forming TiC layer which is continuous at higher speeds known as chemical wear process, leading to crater formation on tool material as observed by earlier researchers. The occurrence of crater wear might be due to chip-tool contact stresses generation, depleting the C and Co from cutting tool. An adherent layer of TiC formation exists on the cutting edge due to the chemical reaction between the titanium workpiece and the cutting tool material. Formation of oxycarbides on the surface indicates the existence of oxygen. Earlier researchers suggested this existence by Auger spectroscopy Analysis. Researchers also suggested that TiC grains removal might be taking place from the cutting tool because of reduction in toughness as the diffusion process takes place. Replenishing of TiC grains on the tool surface will probably occur by obtaining C from WC grains [3, 12–17, 21–29, 32]. The presence of Mo, Ni, Br, Cr, Fe and V indicates the work material composition diffusivity to the tool tip. Sulphur (S), silicon (Si) and magnesium (Mg) act as protective layer or barrier for adhesive wear and prevent the welding and stiffening of the work material in the tool surface. Through EDS analysis, it can be predicted that coating delamination in the initial stages may be due to mechanical wear later on by chemical mechanisms.
