Grindability improvement of Ti-6Al-4V using cryogenic cooling

Abstract

Titanium and its alloys are well known for their difficult machinability nature. Because of Ti-6Al-4V alloy's strong chemical affinity, high temperature and pressure during the grinding process, the formed chips easily weld onto the grinding wheel surface. This phenomenon reduces the wheel life and diminish the surface quality. To control the effect of temperature, most grinding operations today employ cutting fluids. These fluids help in improving the surface quality and increasing the wheel life. However, because of environmental and economic concerns, industries are now looking for sustainable alternative cooling techniques such as cryogenic cooling. The aim of this study is to present the application of liquid nitrogen cryogenic cooling as an alternative cooling technique for grinding Ti-6Al-4V alloys. To compare the effect of cryogenic condition, experiments were conducted under both dry and wet (soluble oil) conditions. Experimental results proved the effectiveness of cryogenic cooling in reducing the grinding force, obtaining better surface finish, and being less damaging to the surface condition. Finally, multiple regression models were developed to predict the normal force and tangential force in cryogenic condition. The developed models have been validated with experimental data, and the maximum prediction error of the model for normal and tangential forces was less than 12% and 9%, respectively.

Some investigations in grindability improvement of Inconel 718 under ecological grinding

“…The application of soluble oil in MQL mode and LN 2 jets significantly reduces normal force component thereby ensuring the retention of grit sharpness for a longer duration due to a reduction in grinding zone temperature resulting in lesser wheel wear. 35 Overall percentage reduction in F n by 10%, 15%, and 20% in the case of wet, MQL, and LN 2 grinding has been found. Moreover, Figure 4 shows an increase in F n with an increase in table speed and depth of cut, which well agrees with the grinding basics.…”

“…In LN 2 grinding, this decrease in F t is due to excellent lubricity between the mating surfaces due to the formation of the lubricating film along the wheel periphery, which further assist in improving the slipping of abrasive grits over the work surface. 35 Formation of MQL lubricating film between the mating surfaces could be the reason behind the reduction in F t in MQL grinding. 33 Smaller F t further aids in retaining the sharpness of grains for longer duration resulting in lesser heat generation.…”

“…This was attributed to improved lubrication in case of MCG grinding. Setti et al 35 investigated the grindability of Ti-6Al-4V using LN 2 as grinding medium. They compared the obtained grinding forces, R a , and wheel wear with dry and wet (soluble oil) grinding.…”

Abrasive machining of advanced aerospace alloys and composites

“…Similarly, the application of minimum quantity lubrication (MQL) with vegetable and synthetic ester based oils led to a two-fold decrease in forces compared to flood cooling when grinding Ti-64, albeit at the cost of increased workpiece surface roughness [187]. Conversely, only a marginal reduction in tangential forces ($15%) was recorded when surface grinding Ti-64 under cryogenic cooling environment in contrast to wet soluble oil conditions [191]. However, cryogenic cooling was rendered ineffective at higher wheel speeds (25 m/s) as the liquid N 2 mist failed to penetrate the grit-chip interface.…”

Grinding temperature and wheel wear of porous metal-bonded cubic boron nitride superabrasive wheels in high-efficiency deep grinding

“…In general, similar to the vitrified abrasive wheels, 46–48 the wear feature of a porous metal-bonded CBN wheel is mainly governed by the strength of the wheel constituents, bonding material and CBN grains under the given grinding loads. Figure 10 provides the schematic illustration and photography of different wear patterns of the porous metal-bonded CBN wheel, that is, abrasion wear or grain fracture, chips loading, and grain pullout.…”