ISSN: 2454-1362, Tool Wear ... · Drill tool dynamometer was used to measure ... The experiment was conducted for different drill bits with machining parameters as shown in below

Imperial Journal of Interdisciplinary Research (IJIR) Vol-2, Issue-8, 2016 ISSN: 2454-1362, http://www.onlinejournal.in

Imperial Journal of Interdisciplinary Research (IJIR) Page 1277

Tool Wear, Surface Roughness, and Power Requirement for Drilling Operation Using

Uncoated and Coated HSS Tool

Karthik V1 & Puneeth H V2 1Research scholar, Department of Mechanical Engineering, New Horizon College of

Engineering, Bengaluru, India 2Assistant Professor, Department of Mechanical Engineering, New Horizon College of

Engineering, Bengaluru, India

Abstract: Drilling is a machining operation of producing cylindrical hole in solid work piece by means of revolving tool called drill bit. Twist drills are the tools used to carry out drilling operation by rotating the cutting tool. Coating the drill bit improves tool life, surface finish and hardness of drill bits. This paper compares the characteristics of HSS drill bit with Titanium Nitride (TiN) and Titanium Aluminium Nitride (TiAlN) coated on HSS for machining of EN8 material under dry machining condition. Parameters such as tool wear, surface roughness, and power required during machining of EN8 material for uncoated HSS and Titanium Nitride, Titanium Aluminium Nitride coated HSS drill bit are found out. Experimental results showed that tool wear was less in TiAlN coated HSS drill bit compared to uncoated HSS, TiN coated HSS. The surface roughness of the hole drilled using TiAlN coated HSS was found to be minimum compared to uncoated HSS and TiN coated HSS tool. Power required to drill holes was calculated and it was found that TiAlN coated HSS tool required more power to in comparison with TiN coated HSS and uncoated HSS tools. Keywords: Twist drills; Uncoated HSS drill; TiN and TiAlN Coated HSS drill; EN8 steel 1. Introduction

Drilling involves the creation of holes that are right circular cylinders. This is accomplished most typically by using a twist drill by rotating it against the workpiece [5]. Drilling machines are used to perform the drilling operation.

Figure 1. Drilling Process

Twist drills has critical or sharp twisted edges shaped around body, hence twist drills are called end cutting tool consisting of one or more cutting lips and cutting teeth with helical flutes which help in chip removal. These helical grooves or flutes form cutting edges by removing chip from workpiece [5]. Twist drills are available in tapered shank or straight shank. In the current study straight shank twist drill was used. The different type of material chosen plays an important role in performance and life of drill bit. The commonly used materials includes

High speed steel:. It is an alloyed steel of 14-22% tungsten with molybdenum, chromium, vanadium, and cobalt. HSS drill tools are categorized in to two types namely T-type(12-18% tungsten) and M-type(10% molybdenum). About 95% of M-type series is used in manufacturing of HSS drills [5]. It has some important characteristics properties like: heat resistance, harder, remain sharper during drilling of long time.

Figure 2. High Speed Steel (HSS) drill tool

Titanium nitride (TiN) coated drills: It is an

hard ceramic material coated to HSS drills. TiN is very hard and inert material, thin film coatings applied to the metal parts. Titanium nitride is a combination of toughness, hardness and inertness. Physical vapor deposition (PVD) system is the

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environmental safe coating method, for coating thin film on HSS tool. Applying TiN coating to metals improves surface chatacteristics. The coated TiN has gold colour with ultra hard material [4, 9]. It has very high chemical resistance which will not corrode during drilling. It has high temperature withstand capacity up to 600ºC, and non-toxic.

Figure 3. Titanium Nitride (TiN) drill tool

Titanium Aluminium nitride (TiAlN): Titanium nitride developes thin film coating of Titanium Aluminium nitride (TiAlN), which offers very high temperature resistance than TiN. It has good hardness property at high temperature, and hence used in high temperature which exceeds limit of TiN. TiAlN coating can withstand higher temperature up to 800ºC it has good oxidation resistance, low in friction and hard coating [4, 9]. It has 3-6 micrometer coating thickness, and has longer tool life of 3 to 10 times than uncoated tools.

Figure 4. Titanium Aluminium Nitride (TiAlN) drill

tool

Tool wear: The tool wear is regularly linked with cutting tools, and defines its slow failure due to regular operation. It is the tribological reaction between tool and new cut surface of work chip and will be under high temperature and pressure. Cutting tool is grinded at different angles to perform cutting operation effectively on various materials and in varying feed, speed and depth of cut [6-10]. Tool life decreases as increase in tool wear. Tool wear cannot be avoided but can be minimized by different operating conditions.

Figure 5. View of different wear on drill tool

Surface roughness: The surface roughness of machined hole is measured in sequence to analyze the quality of the surface finish. Using twist drills machining any product the surface roughness could affect the product operation quality, for example the wearing of parts, surface friction, heat transmission, and light reflection [2-3]. The surface roughness is represented as Ra, Arithmetic mean deviation. To measure surface roughness of machined hole, mitutoyo surface roughness tester was used.

Figure 6. Profile graph of arithmetic mean deviation

(Ra)

Power required: It is important to calculate the power required to drill the hole, because it comes under economical consideration. The power required must be at optimized conditions. If N= speed of drill in rev/minute, then work done/minute= 2πNT Newton meter. Therefore power required is given by equation:

Power= kW.

Where, N= speed of drill, RPM T= Torque, kg-m 2. Literature Review

A. Rivero et al. [1] presented a paper on “An experimental investigation of the effect of coating and cutting parameters on the dry drilling performance of aluminium alloys”. The above paper shows and presents an experimental research study on machinability in the dry drilling of aluminium alloys and on the potential of the new design of tools and coatings. Dry drilling tests were conducted by uncoated drills and two different coatings prepared





by arc evaporation PVD process. Experiments consisted of drilling of 10mm diameter three edged drill to produce 25mm deep holes. Burr size and tool wear were analyzed with the impact of process parameters on torque, power, feed force and tool temperature. The above paper concluded that, increasing force and feed rate burr size can be reduced. By decreasing power, workpiece temperature can be controlled.

Gijven Meral et al. [2] presented a paper on

“Multi-response optimization of cutting parameters for hole quality in drilling of AISI 1050 steel”. Experiments on the dimensional accuracy, surface roughness, circular and cylindrical deviation characterizing hole quality was investigated practically. The reference material AISI 1050 steel was chosen to carry out experiment since it had wide applications in many areas. Uncoated HSS and coated TiAlN by physical vapor deposition (PVD) with different were used. After conducting each experiment, hole properties such as dimensional accuracy, surface roughness, circular deviation and axial misalignment between outlet and inlet holes, finally hole quality was measured and results evaluated with statistical analysis was carried out to indicate effect of drill parameters on tests results. The coated tools compared with uncoated tools resulted positive results. The important parameter on surface roughness was drill diameter. The effective parameter on circular, dimensional accuracy and cylindrical deviation was cutting speed for both coated and uncoated tools except cylindrical deviation occurring in uncoated drill.

M. Pirtini, I. Lazoglu [3] presented a paper on

“Forces and hole quality in drilling”. In the experimental investigation, a new mathematical model based on the mechanics and dynamics of the drilling mechanism was improvised for the exaggeration of cutting force and hole quality. A new technique was also explained in order to obtain cutting coefficients directly from a group of comparatively simple calibration tests. It was found that it was easy to stimulate the cutting forces for different cutting conditions in the process of planning stage using only the model. In the structural dynamic model, frequency functions of spindle and tool system were integrated into model to obtain hole profile.

Kadam M. S and Pathak S. S [4] presented a

paper on “Experimental analysis and comparative performance of coated and uncoated twist drill bit dry machining”. A practical research was carried out to check the effect of input machining parameters feed rate, cutting speed, point angle and diameter of drill bit on CNC machine under dry condition. The comparative study of single layer Titanium

Aluminium Nitride (TiAlN) and High speed steel tool for EN31 steel under dry condition was made. The experimentation describes Analysis of Variance to validate of established mathematical models for depth analysis of finish drilling process parameters on torque, machine time and chip load. The above analysis concluded that, there was a minimum machining time required under 1200rpm cutting speed, 0.18mm/rev feed rate and 6mm drill diameter. The torque required was minimum when feed rate was 0.14mm/rev, speed of 1600rpm and drill diameter of 6mm. 3. Objective and methodology 3.1 Objective

The main objective of this investigation was to compare the characteristics such as tool wear, surface roughness and power calculations of uncoated HSS drill bit with Titanium Nitride (TiN), and Titanium Aluminium Nitride (TiAlN), coated HSS drill bit for machining of EN8 material. These characteristics were studied under constant speed, feed and depth of cut. 3.2 Methodology

From the literature review, HSS, TiN coated HSS and TiAlN coated HSS twist drills were selected for machining of EN8 material. To check the tool condition monitoring of coated and uncoated drill bits, different parameters were considered such as tool wear, surface roughness, and power required. To study the above mentioned characteristics, different methodologies were involved such as tool wear using metallurgical microscope and SEM, surface roughness by surface roughness tester machine, and power calculations by mathematical equation.

Figure 7. Flow chart of Methodology





4. Experimental setup

Radial drilling machine was used under dry machining condition to carry out investigations of uncoated HSS and coated HSS twist drills in drilling of EN8 steel workpiece.

Drill tool dynamometer was used to measure

cutting forces; the cutting forces measured included thrust force and torque which was developed during drilling of hole in the workpiece. Thrust force was measured along axial direction and torque was produced due to rotation of drill. Drill tool dynamometer offer load as well as torque output. The drill tool dynamometer is placed on the work platform and workpiece is located on dynamometer. The power supplied to dynamometer was 230V, 50Hz mains supply.

Figure 8. Experimental set-up of drilling machine

Figure 9. Drill tool dynamometer

In the current experimental investgation, EN8

steel was chosen as workpiece material. EN8 is an unalloyed medium carbon steel; it has a greater tensile strength compared with mild steel. EN8 can be machined at any condition; surface hardening can be done to improve wear resistance. Hardness ranges from 50-55HRC. EN8 is tempered between 550-600ºC. It is suitable for manufacturing gears, shafts, studs, bolts, keys, pins, connecting rods, axels, and

rollers. EN8 is also used in manufacturing of Continuous Variable Transmission (CVT) clutch.

Figure 10. EN8 workpiece

The chemical composition and mechanical properties are mentioned below:

Table 1. EN8 Steel properties

The experiment was conducted for different drill bits with machining parameters as shown in below table 2. The EN8 steel workpiece material dimensions was 140*140*13mm.

Table 2. Machining parameters

Table 3. Drill bit specification





Figure 11. Drilled EN8 workpiece

5. Results and discussion 5.1 Tool wear:

Tool wear of twist drill was analyzed using Inverted Metallurgical microscope and Scanning Electron Microscope (SEM). The comparison was made between uncoated and coated HSS drill. 5.1.1 Uncoated HSS tool wear data:

Figure 12. Measurement of point tip wear on HSS tool

before start of drill

Figure 13. Measurement of corner wear on HSS tool before start of drill

Figure 14. Measurement of point tip wear on HSS tool

at 20th (final) hole

Figure 15. Measurement of corner wear on HSS tool at

20th hole

Figures 12 to 15 shows tool wear at point tip length L1 and width W1along with corner wear of uncoated HSS drill for initial and final 20th hole. Experimental studies showed the tool failed to drill beyond 20th hole for uncoated HSS twist drill. The tool wear in terms of point tip width increased to 240.037 microns for the final hole. The length at the point tip decreased to 111.01 microns and corner length of the tool decreased by 192.71 microns indicating increase in tool wear. Table 4. HSS drill tool point tip and corner wear data





Figure 16. Graph of Uncoated HSS tool point tip and

corner wear The above graph represents that decrease in

length at point tip and corner portion of uncoated HSS drill tool indicates increase in tool wear whereas increase in width represents increase in tool wear.

Figure 17. SEM images of worn out uncoated HSS drill

at tool point tip

Figure 18. SEM images of worn out at corner of

uncoated HSS drill tool

5.1.2 Titanium Nitride (TiN) coated HSS drill tool wear data:

Figure 19. Measurement of point tip wear on TiN

coated HSS tool before start of drill

Figure 20. Measurement of corner wear on TiN coated

HSS tool before start of drill

Figure 21. Measurement of point tip wear on TiN

coated HSS tool at 80th (final) hole





Figure 22. Measurement of corner wear on TiN coated

HSS tool at 80th (final) hole

Figures 19 to 22 shows tool wear at point tip length L1 and width W1along with corner wear of TiN coated HSS drill for initial and final 80th hole. Experimental studies showed the tool failed to drill beyond 80th hole for TiN coated HSS twist drill. The tool wear in terms of point tip width increased to 941.796 microns for the final hole. The length at the point tip decreased to 185.055 microns and corner length of the tool decreased by 427.17 microns indicating increase in tool wear.

Table 5. TiN coated HSS drill tool wear data

Figure 23. Graph of TiN coated HSS drill tool wear

The above graph represents that decrease in length at point tip and corner portion of TiN coated HSS drill tool indicates increase in tool wear whereas increase in width represents increase in tool wear.

Figure 24. SEM images of worn out TiN coated HSS

drill at tool point tip

Figure 25. SEM images of worn out at corner of TiN

coated HSS drill tool 5.1.3 Titanium Aluminium Nitride (TiAlN) coated HSS drill tool wear data:

Figure 26. Measurement of point tip wear on TiAlN

coated HSS tool at 10th hole





Figure 27. Measurement of corner wear on TiAlN

coated HSS tool at 10th hole

Figure 28. Measurement of point tip wear on TiAlN


Figure 29. Measurement of corner wear on TiAlN


Figures 26 to 29 shows tool wear at point tip length L1 and width W1along with corner wear of TiAlN coated HSS drill for initial and final 110th hole. Experimental studies showed the tool failed to drill beyond 110th hole for TiAlN coated HSS twist drill. The tool wear in terms of point tip width increased to 471.532 microns for the final hole. The length at the point tip decreased to 747.982 microns and corner length of the tool decreased by 864.297 microns indicating increase in tool wear.

Table 6. TiAlN coated HSS drill tool wear data

Figure 30. Graph of TiAlN coated HSS drill tool point

tip and corner wear

The above graph represents that decrease in length at point tip and corner portion of TiAlN coated HSS drill tool indicates increase in tool wear whereas increase in width represents increase in tool wear.

Figure 31. SEM images of worn out TiAlN coated HSS

drill at tool point tip





Figure 32. SEM images of worn out at corner of TiAlN

coated HSS drill tool 5.2 Surface roughness: The surface roughness of drilled hole is measured to analyze the quality of the surface finish. To measure the surface roughness of drilled hole, mitutoyo surface roughness tester was used. The arithmetic mean deviation (Ra) was measured for the drilled holes. 5.2.1 Holes drilled using HSS drill: surface roughness in arithmetic mean deviation (Ra): Table 7. Surface roughness measured for drilled holes

using uncoated HSS drill

Figure 33. Graph of surface roughness in terms of Ra

for uncoated HSS tool drilled holes Above graph represents continuous increase in surface roughness (Ra) up to 1.121 microns in uncoated HSS tool drilled holes.

5.2.2 Holes drilled using TiN coated HSS drill: surface roughness in arithmetic mean deviation (Ra): Table 8. Surface roughness measured for drilled holes

using TiN coated HSS tool

Figure 34. Graph of surface roughness in terms of Ra

for TiN coated HSS tool drilled holes The above graph represents continuous increase in

surface roughness (Ra) up to 2.4 microns in TiN coated HSS tool drilled holes. 5.2.3 Holes drilled using TiAlN coated HSS drill: surface roughness in arithmetic mean deviation (Ra): Table 9. Surface roughness measured for drilled holes

using TiAlN coated HSS tool





Figure 35. Graph of TiAlN coated HSS tool drilled holes surface roughness Ra

The above graph represents continuous increase in

surface roughness (Ra) up to 1.058 microns in TiAlN coated HSS tool drilled holes. 5.3 Power required: For economic consideration, it is very important to calculate the power required during drilling operation. The power requires during drilling is given by the equation:

Power= kW.

Where, N= speed of drill, RPM T= Torque, kg-m 5.3.1 Power required during drilling operation using uncoated HSS tool:

Table 10. Power calculations for uncoated HSS tool

Figure 36. Graph of power required during drilling

holes using uncoated HSS tool

5.3.2 Power required during drilling operation using Titanium Nitride (TiN) coated HSS tool:

Table 11. Power calculation for TiN coated HSS tool


holes using TiN coated HSS tool 5.3.3 Power required to drill hole using Titanium Aluminium Nitride (TiAlN) coated HSS tool: Table 12. Power calculation for TiAlN coated HSS tool


holes using TiAlN coated HSS tool 6. Conclusion

Scanning Electron Microscope (SEM) and

Inverted Metallurgical microscope used to calculate tool wear showed that uncoated HSS had an increased tool wear for minimum drilled holes (20 holes) whereas TiN and TiAlN coated HSS tool showed increased wear with increase in number of holes drilled (80 and 110 holes respectively). The surface roughness in arithmetic mean deviation (Ra) measured using mitutoyo surface roughness tester indicated TiAlN coated HSS drill had minimum surface roughness in comparison with TiN coated HSS and uncoated HSS drill.





Experimental Power calculations indicated TiAlN coated HSS drill required increased power for more number of holes in comparison with TiN coated HSS and uncoated HSS drill.

7. References [1] A. Rivero, G. Aramendi, S. Heranz, L.N. Lopezde Lacelle “An experimental investigation of the effect of coating and cutting parameters on the dry drilling performance of aluminium alloys” Int J Adv Manuf Technol (2006) 28: 1-11. [2] Gijven Meral, Murat Sarikaya, Hakan Dilip, Ulvisekev “Multi-response optimization of cutting parameters for Hole quality in Drilling of AISI 1050 steel” Arab J Sci Eng (2015) 40:3709-3722. [3] M. Pirtini, I. Lazoglu “Forces and hole quality in drilling” International Journal of Machine Tools and Manufacture 45(2005) 1271-1281. [4] Kadam M.S, Pathak S.S “Experimental Analysis and comparative performance of coated and uncoated Twist drill bit dry machining” ISSN: 2249-5762(online) IJRMET vol.1, Issue 1, Oct 2011. [5] Dhanraj Patel “Analysis of drilling tool life- A Review” Int. J. Mech. Eng. and Rob. Res. 2015, ISSN 2278-0149. [6] Erkki Jantunen “A summary of methods applied to tool condition monitoring in drilling” International Journal of Machine tool and Manufacture 42(2002) 997-1010. [7] S. Dolinsek, J. Kopac “Mechanism and types of tool wear; particularities in advanced cutting materials” JAMME Volume 19 Issue 1 November 2006. [8] Anil Jindal “Analysis of tool wear rate in drilling operation using scanning electron microscope (SEM)” Journal of Minerals and Materials Characterization and Engineering, Vol.11, No.1, PP.43-54, 2012. [9] R.J. Talib, M.R.M. Toff and H.M. Ariff “Wear Mechanism of TiN, TiAlN and TiCN coated drills during drilling of carbon steel” Journal of physical science, Vol.18(1), 75-85, 2007. [10] A. Meena, M. EI Mansori “Specific cutting forces, tool wear and chip morphology characteristics during dry drilling of Austempered ductile iron (ADI)” Int. J. Adv. Manuf. Technol (2013)69: 2833-2841.



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ISSN: 2454-1362, Tool Wear ... · Drill tool dynamometer was used to measure ... The experiment was conducted for different drill bits with machining parameters as shown in below