Analysis of Surface Hardness, Surface Roughness, and Near Surface Microstructure of AISI 4140 Steel Worked with Turn-Assisted Deep Cold Rolling Process

In the present study, response surface methodology has been used to optimize turn-assisted deep cold rolling process of AISI 4140 steel. A regression model is developed to predict surface hardness and surface roughness using response surface methodology and central composite design. In the development of predictive model, deep cold rolling force, ball diameter, initial roughness of the workpiece, and number of tool passes are considered as model variables. The rolling force and the ball diameter are the significant factors on the surface hardness and ball diameter and numbers of tool passes are found to be significant for surface roughness. The predicted surface hardness and surface roughness values and the subsequent verification experiments under the optimal operating conditions confirmed the validity of the predicted model. The absolute average error between the experimental and predicted values at the optimal combination of parameter settings for surface hardness and surface roughness is calculated as 0.16% and 1.58% respectively. Using the optimal processing parameters, the surface hardness is improved from 225 to 306 HV, which resulted in an increase in the near surface hardness by about 36% and the surface roughness is improved from 4.84µm to 0.252 µm, which resulted in decrease in the surface roughness by about 95%. The depth of compression is found to be more than 300µm from the microstructure analysis and this is in correlation with the results obtained from the microhardness measurements. Taylor hobson talysurf tester, micro vickers hardness tester, optical microscopy and X-ray diffractometer are used to characterize the modified surface layer. 

• P. R. Prabhu
• S. M. Kulkarni
• S. S. Sharma
• K. Jagannath
• Achutha Kini U.

• Surface hardness
• response surface methodology
• microstructure
• central composite design
• deep cold rolling
• surface roughness.

[1] Seemikeri, C. Y., Brahmankar, P. K., Mahagaonkar, S. B., 2008,
Investigations on surface integrity of AISI 1045 using LPB tool.
Tribology International 41, 724-734.
[2] Axinte, D. A., Gindy, N., 2004, Turning assisted with deep cold rolling
– a cost efficient hybrid process for workpiece surface quality
enhancement. Proceedings of Institution of Mechanical Engineers 218,
807-811.
[3] Gill, C. M., Fox, N., Withers, P.J., 2008, Shakedown of deep cold
rolling residual stresses in titanium alloys. Journal of Physics D, Applied
Physics, 1-5.
[4] El-Khabeery, M. M., El-Axir, M. H., 2001, Experimental techniques for
studying the effects of milling roller burnishing parameters on surface
integrity. International Journal of Machine Tools and Manufacture 41,
1705-1719.
[5] Nalla, R. K., Altenberger, I., Noster, U., Liu, G. Y., Scholtes, B.,
Ritchie, R.O., 2003, On the influence of mechanical surface treatments -
deep rolling and laser shock peening on the fatigue behaviour of Ti–
6Al–4V at ambient and elevated temperatures. Materials Science and
Engineering A 355, 216-230.
[6] David Matlock, K., Khaled Alogab, A., Mark Richards, D., John Speer,
G., 2005, Surface Processing to Improve the Fatigue Resistance of
Advanced Bar Steels for Automotive Applications. Materials Research
8, 453-459.
[7] Altenberger, I., Juijerm, P., 2007, Effect of high temperature deep
rolling on cyclic deformation behaviour of solution heat treated Al-MgSi-Cu
alloy. Scripta Materialia 56, 285–288.
[8] Tsuji, N., Tanaka, S., Takasugi, T., 2008, Evaluation of surface modified
Ti-6Al-4V alloy by combination of plasma carburizing and deep rolling.
Materials Science and Engineering A 488, 139-145.
[9] Majzoobi, G.H., Azadikhah, K., Nemati, J., 2009, The effects of deep
rolling and shot peening on fretting fatigue resistance of aluminium
7075-T6. Materials Science and Engineering A 516, 235-247.
[10] Oberg, E., Green, R.E., 1996, Machinery’s Handbook, 25th edition,
Industrial Press Inc., New York.