Experimental Investigation of the Influence of Burnishing Parameters on Surface Roughness and Surface Hardness of Aluminium Alloy 6061 T6 on CNC machine

Experimental Investigation of the Influence of Burnishing Parameters on Surface Roughness and Surface Hardness of Aluminium Alloy 6061 T6 on CNC machine

Sumitkumar S. Loriya1

1M.E (Production Engineering) student 1Department of Mechanical Engineering,

LDRP-ITR Gandhinagar, Gujarat, India.

Vijay Patel2

2 Asst. Professor, 2Department of Mechanical Engineering, LDRP-ITR Gandhinagar, Gujarat, India.

Abstract: In this paper, ball burnishing as a mechanical surface treatment for improving productivity and quality of rotating shafts is presented. When this method is applied after conventional turning, the resulting process is rapid, simple and cost effective, directly applicable in lathes, CNC and turning centers of production lines. This process provides good surface finish, and surface hardness increment of the surface layer, which in turn improves wear resistance, increases corrosion resistance, improves tensile strength, maintains dimensional stability and improves the fatigue strength of the work piece.

Results show that burnishing is an economical and feasible mechanical treatment for the quality improvement of rotating components, not only surface roughness but in surface hardness as well.

Keywords: Ball burnishing tool, CNC machine, Aluminium, Surface roughness, Surface Hardness.

1. INTRODUCTION

In todays manufacturing industry, special attention is given on surface finish along with dimensional accuracy and geometrical tolerance. Comparing with other finishing process such as grinding, honing, burnishing is chip less process. Burnishing is a cold working surface finishing process which is carried out on material surfaces to induce compressive residual stresses and enhance surface qualities. A burnishing tool typically consists of a hardened sphere which is pressed onto across the part being processed which results in plastic deformation of asperities into valleys. In burnishing process the initial asperities are compressed beyond yield strength against load. The surface of the material is progressively compressed, then plasticized as resultant stresses reach a steady maximum value and finally wiped a superfine finish.

The burnishing process, shown in Fig 1 is based on the rolling movement of a ball against the work piece surface, a normal force being applied at the tool. As soon as the yield point of the work piece material is exceeded, plastic flow of the original asperities takes place. This phenomenon leads to a smoother surface. At the same time, compressive stresses are induced in the surface layer, followed by strain hardening and a series of beneficial effect on mechanical properties. Burnishing can improve both the surface strength

and roughness. The increase of surface strength mainly serves to improve fatigue resistance under dynamic loads.

Fig 1 Schematic diagram of Ball Burnishing Process[9]

Burnishing is a cold working process in which plastic deformation occurs by applying a pressure through a ball or roller on metallic surfaces as shown in Fig 2. It is a finishing and strengthening process. Improvements in surface finish, surface hardness, wear resistance, fatigue resistance, yield and tensile strength and corrosion resistance can be achieved by the application of this process.

Burnishing is one of the important finishing operations carried out generally to enhance the fatigue resistance characteristics of components. Burnishing tools are used to impart a gloss or fine surface finish, often in processes that involve the cold working of metal surfaces. Burnishing tools are also used for the sizing and finishing of surfaces. Burnishing tool can be a roller or ball type.

Fig. 2 Ball Burnishing Process [16]

Burnishing process can be typically classified into two categories as:

1. Based on deformation element

   1. Ball burnishing

      1. Flexible

      2. Rigid

   2. Roller burnishing

2. Based on the motion of the tool, on the surface

   1. Normal or ordinary

   2. Impact

   3. Vibratory

1. EXPERIMENTAL SETUP

   2.1. Work piece material

   In this work, Aluminium alloy 6061 T6 was used as a workpiece material. which were received as 40 mm diameter round bars. These bars are cut to suitable lengths of 200 mm and then turned to 38 mm diameter. Each work piece was divided into 5 regions of 30 mm each by a slot of 2 mm length and 2 mm depth. The chemical composition and mechanical properties of the material are shown in Tables 1 & 2.

   The burnishing tool designed shown above consists of parts namely ball, cover plate, main tool body and plate screw. The ball is made up of EN31 (High carbon alloy steel) having diameter 10 mm and the body is made up of mild steel. The design is made in consideration with the parameters in the work i.e. input parameters are Burnishing speed, Feed rate, Depth of penetration & Coolant and output parameters are Surface Roughness & Surface Hardness.

   1. Machine Tool

      1. CNC Machine

   The Experiment was carried out on a Turn Master GF 165-A CNC Machine tool shown in Fig. 4

   Table 1 Chemical composition

   %Si %Fe	0.918 0.291	(a)
   %Cu	0.072
   %Mn	0.688
   %Mg	0.871
   %Cr	0.070
   %Zn	0.031

   %Ti 0.062

   Table 2 Mechanical properties

   Hardness, HV5 99.33

   Ultimate Tensile Strength 275-375 MPa

   Elongation % 4.0-16.0

   This material is selected due to its importance in aeronautic/aerospace industries and also in automobile industries.

   2.2. Ball Burnishing Tool

   Many researchers have done their experiments by developing different types of burnishing tools like ball burnishing tool and roller burnishing tool and use them with conventional machine tools. But in our work we have made a tool which can be used in CNC machine as shown in Fig. 3. The design is made in such a manner that the tool is simple, cheaper and can be used easily.

   Fig. 3 Ball Burnishing Tool

   (b)

   Fig. 4 (a) & (b) CNC machine tool

   1. Roughness Tester

      The roughness tester used for measuring surface roughness of aluminium bar is Mitutoyo SJ210 roughness tester shown in fig. 5 and its measurement range is -200µm to 160µm.

      Fig. 5 Surface Roughness Tester

   2. Hardness Tester

   The Hardness Tester used for measuring Surface

   Table 4 Trial Experiments

   Hardness of aluminium bar is Vickers Hardness Testing

   Machine, shown in Fig. 6

   Speed (mm/min)

   Feed (mm/rev)

   Depth of penetration (mm)

   Roughness (m)

   Fig. 6 Surface Hardness Tester

2. EXPERIMENTATION

   The Experiments were planned according to L27 orthogonal array, which has 27 rows corresponding to the number of experiments with 3 columns at 3 levels, as shown in Table 3.

   50 0.1 0.1 0.571

   100 0.1 0.1 0.302

   150 0.1 0.1 0.346

   200 0.1 0.1 0.223

   240 0.1 0.1 0.343

   200 0.05 0.1 0.213

   200 0.12 0.1 0.261

   200 0.15 0.1 0.289

   200 0.07 0.05 0.243

   200 0.07 0.1 0.232

   200 0.07 0.15 0.655

   The roughness and hardness of the burnished aluminium was measured at each specified region with the help of the Mitutyo SJ210 surface roughness tester & Vickers Hardness Testing Machine, and the average values of several measurements were reported for each region.

   Table 5

   Experimental data for Surface Roughness

   Table 3 Parameters and their levels.

   Speed (mm/min)

   Feed (mm/rev)

   Depth of

   		(mm)	(m)
   190	0.05	0.05	0.503
   190	0.05	0.075	0.284
   190	0.05	0.1	0.261
   190	0.07	0.05	0.560
   190	0.07	0.075	0.182
   190	0.07	0.1	0.265
   190	0.1	0.05	0.336
   190	0.1	0.075	0.387
   190	0.1	0.1	0.369
   200	0.05	0.05	0.128
   200	0.05	0.075	0.196
   200	0.05	0.1	0.213
   200	0.07	0.05	0.233
   200	0.07	0.075	0.238
   200	0.07	0.1	0.495
   200	0.1	0.05	0.387
   200	0.1	0.075	0.330
   200	0.1	0.1	0.268
   210	0.05	0.05	0.478
   210	0.05	0.075	0.280
   210	0.05	0.1	0.289
   210	0.07	0.05	0.178
   210	0.07	0.075	0.124
   210	0.07	0.1	0.115
   210	0.1	0.05	0.588
   210	0.1	0.075	0.329
   210	0.1	0.1	0.332

   penetration

   Surface

   Roughness

   	1		3
   Burnishing mm/min Speed	190	200	210
   Feed rate mm/rev	0.05	0.07	0.1
   Depth of Penetration Mm	0.05	0.075	0.1

   Parameters Unit Level Level 2 Level

3. RESULTS AND DISCUSSIONS

   Initially the work piece was measured for its initial surface roughness and initial surface hardness i.e., initial surface roughness was 1.762 m & Initial surface hardness was 99.33 HV5 and then the trial experiment was done shown in Table 4 and finally the Experiment was carried out with the parameters and levels mentioned in table 3 as shown in Table 5 & 6. And the work pieces after Burnishing are shown in Fig 7.

   Fig. 7 Work pieces after Burnishing

   Table 6 Experimental data for Surface Hardness

   Effects of Feed rate

   The investigation into the effect of Feed rate,

   			(HV5)
   190	0.05	0.05	103.00
   190	0.05	0.075	106.33
   190	0.05	0.1	115.00
   190	0.07	0.05	110.00
   190	0.07	0.075	108.00
   190	0.07	0.1	108.33
   190	0.1	0.05	111.00
   190	0.1	0.075	119.67
   190	0.1	0.1	128.33
   200	0.05	0.05	106.67
   200 200	0.05 0.05	0.075 0.1	113.33 112.33
   200	0.07	0.05	108.00
   200	0.07	0.075	113.00
   200	0.07	0.1	109.33
   200	0.1	0.05	111.00
   200	0.1	0.075	107.33
   200	0.1	0.1	105.67
   210	0.05	0.05	103.00
   210	0.05	0.075	114.33
   210	0.05	0.1	115.33
   210 210	0.07 0.07	0.05 0.075	111.67 109.67
   210	0.07	0.1	107.00
   210	0.1	0.05	115.00
   210	0.1	0.075	112.00
   210	0.1	0.1	108.00

   Speed (mm/min)

   Feed (mm/rev)

   Depth of penetration (mm)

   Surface Hardness

   during the ball burnishing process of aluminium found that

   initially, the surface roughness decreases with an increase in feed rate to a certain limit and then starts increases beyond that. In case of surface Hardness with an increase in feed rate the surface hardness increases.

   Effects of Depth of penetration

   An investigation of effect of depth of penetration on the surface roughness of aluminium rod shows that increase in the depth of penetration results in increase in burnishing force, which in turns decreases the surface roughness value to certain limit and then starts increases. In case of surface hardness, with the increase in depth of penetration the surface hardness increases to a certain limit and then starts decreases.

   Effects of Coolant

   An investigation of effect of coolant shows that during the working condition, due to the high speed and aluminium as work piece the temperature on the surface of aluminium increases and starts sticking on the surface of burnishing ball, which in turn increases the surface roughness. So, during burnishing process mist coolant is required.

   Table 7

   Optimum parameter values for surface roughness

   Burnishing Speed (mm/min)

   Feed rate (mm/rev)

   Depth of penetration (mm)

   Surface roughness (m)

   210 0.07 0.1 0.115

   Table 8

   Optimum parameter values for surface Hardness

   Burnishing Speed (mm/min)

   Feed rate (mm/rev)

   Depth of penetration (mm)

   Surface Hardness (HV5)

   Effects of burnishing speed

   The investigation into the effect of burnishing speed, during the ball burnishing process of aluminium fund that initially, when the speed was increased, the surface roughness of the aluminium work piece decreases up to a certain limit. Then, with further increase in burnishing speed, the surface roughness increases. The possible reason of increase in surface roughness may be the chattering of the ball burnishing tool and the increase in temperature, which increases the possibility of material transformation between the burnishing ball and work piece interface. And in case of surface hardness of the burnished surface the hardness increases with the decrease in Burnishing speed and starts decreasing with the increase in Burnishing speed.

   190 0.1 0.1 128.33

4. CONCLUSIONS

1. Burnishing speed & Feed rate are most affected parameters on surface Roughness.

2. Surface Hardness increases with decrease in Burnishing speed and increase in feed rate.

3. Burnishing with High speed & medium Feed rate gives better Surface Finish.

4. At Burnishing speed = 210 mm/min, Feed rate = 0.07 & Depth of penetration = 0.1, best surface finish obtained i.e., 115 m.

5. At Burnishing speed = 190 mm/min, Feed rate = 0.1 & Depth of penetration = 0.1, best surface hardness obtained i.e., 128.33 HV5.

6. Due to the high heat generation at the surface of work piece, coolant is compulsory required.

REFERENCES:

1. N. M. Qureshi , Vaibhav B. Patil, Basavaraj D. Teli, Vaibhav B. Patil, Basavaraj D. Teli, Analysis of Effect of Ball and Roller Burnishing Processes on Surface Roughness on EN8 Steel, International Journal of Engineering Research & Technology (IJERT) , Vol. 4 Issue 06, June-2015, pg. 311 -315.

2. J.N. Malleswara Rao, A. Chenna Kesava Reddy and P. V. Rama Rao, Experimental investigation of the influence of burnishing tool passes on surface roughness and hardness of brass specimens , Indian Journal of Science and Technology, Vol. 4 No. 9 ,Sep 2011, pg. 1113-118.

3. M.R. Stalin John, A. Welsoon Wilson , A. Prasad Bhardwaj , Avinav Abraham , B.K. Vinayagam, An investigation of ball burnishing process on CNC lathe using nite element analysis, Simulation modeling practice and theory 62 , 2016, pg. 88-101.

4. D.B. Patel and T.M. Patel ,Determination of optimal ball burnishing parameters for surface roughness of aluminium alloy , Journal of Mechanical Engineering and Sciences (JMES) , Volume 4, June 2013, pg. 472-478.

5. P. N. Patel, N.B. Patel, T. M. Patel ,Parametric Optimization of Ball Burnishing Process Parameter for Hardness of Aluminium Alloy 6061 , IOSR Journal of Engineering (IOSRJEN), Vol. 04, Issue 08, August. 2014, pg. 21-26.

6. Pavan Kumar, Purohit G K, Design and Development of Ball Burnishing Tool, AETAME , 2013, pg. 771-775.

7. A. Rodríguez , L.N. López de Lacalle, A. Celaya, A. Lamikiz, J. Albizuri, Surface improvement of shafts by the deep ball-burnishing technique, Surface & coating Technology 206 , 2012, pg. 2817-2824

8. M.H. El-Axir , O.M. Othman, A.M. Abodiena, Improvements in out-of-roundness and micro hardness of inner surfaces by internal ball burnishing process, Journal of material Processing Technology 196 , 2008, pg. 120-128.

9. Fang-Jung Shiou, Shih-Ju Huang, Albert J. Shihb, Jiang Zhu and Masahiko Yoshino, Fine Surface Finish of a Hardened Stainless Steel Using a New Burnishing Tool, Procedia Manufacturing 10, 2017, pg. 207-217.

10. M.H. El-Axir, A.A. Ibrahim, Some surface characteristics due to centre rest ball burnishing, Journal of material Processing Technology 167, 2005, pg. 47-53.

11. Goutam Devaraya Revankar , Raviraj Shetty , Shrikantha Srinivas Rao, Vinayak Neelakanth Gaitonde, Wear resistance enhancement of titanium alloy (Ti6Al4V) by ball burnishing process, Journal of materials research and Technology (JMRTEC)-212, 2016, pg. 1-20.

12. W. Bouzid Sai , K. Sai, Finite element modeling of burnishing of AISI 1042 steel, The International Journal of Advanced Manufacturing Technology (IJAMT) 25,2005, pg. 460-465.

13. Prof. Ghodake A. P., Prof. Rakhade R.D., Prof.Maheshwari A.S., Effect of Burnishing Process on Behavior of Engineering Materials- A Review, IOSR Journal of Mechanical and Civil Engineering (IOSR-JMCE), Volume 5, Issue 5, Mar. – Apr. 2013, pg. 9-20.

14. Deepak Mahajan*, RavindraTajane, A Review on Ball Burnishing Process,International Journal of Scientific and Research Publications, Volume 3, Issue 4, April 2013, pg. 1-8

15. M. Sayahi& S. Sghaier& H. Belhadjsalah, Finite element analysis of ball burnishing process: comparisons between numerical results and experiments,Int J Advanced Manufacturing Technology 67, 2013, pg. 16651673.

16. https://www.researchgate.net/figure/Figure-1-Schematic- representation-of-ball-burnishing-process-17_281734002_fig1

17. http://www.brightbright.com/about_burnishing.html

18. https://www.google.co.in/search?q=ball+burnishing+process

19. https://en.wikipedia.org/wiki/Burnishing

20. http://www.sciencedirect.com/

21. https://www.slideshare.net/JohnsJosepp/burnishing-processsuper- finishing-process