Comparative Evaluation of Surface Quality, Tool Wear, and Specific Cutting Energy for Wiper and Conventional Carbide Inserts in Hard Turning of AISI 4340 Alloy Steel

Abstract

This paper presents an experimental study into the comparative response of wiper and round-nose conventional carbide inserts coated with TiCN + AL₂O₃ + TiN when turning an AISI 4340 steel alloy. The optimal process parameters, as identified by pre-experiments, were used for both types of inserts to determine the machined surface quality, tool wear, and specific cutting energy for different cutting lengths. The wiper inserts provided a substantial improvement in the attainable surface quality compared with the results obtained using conventional inserts under optimal cutting conditions for the entire range of the machined lengths. In addition, the conventional inserts showed a dramatic increase in roughness with an increased length of the cut, while the wiper inserts showed only a minor increase for the same length of cut. A scanning electron microscope was used to examine the wear for both types of inserts. Conventional inserts showed higher trends for both the average and maximum flank wear with cutting length compared to the wiper inserts, except for lengths of 200-400 mm, where conventional inserts showed less average flank wear. A higher accumulation of deposited chips was observed on the flank face of the wiper inserts than the conventional inserts. The experimental results demonstrated that edge chipping was the chief tool wear mechanism on the rake face for both types of insert, with more edge chipping observed in the case of the conventional inserts than the wiper inserts, with negligible evidence of crater wear in either case. The wiper inserts were shown to have a higher specific cutting energy than those detected with conventional inserts. This was attributed to (i) the irregular nose feature of the wiper inserts differing from the simpler round nose geometry of the conventional inserts and (ii) a higher tendency of chip accumulation on the wiper inserts.

Keywords: AISI 4340 steel alloy; conventional round-nose inserts; cutting parameters; specific energy consumption; surface roughness; tool wear; turning operation; wiper inserts.

Figure 1

Cylindrical test piece for the turning tests (dimensions are in mm).

Figure 2

Cutting inserts: (a) conventional insert and (b) wiper insert.

Figure 3

Flank wear in the case of conventional inserts after (a) L = 100 mm, (b) L = 200 mm, (c) L = 300 mm, (d) L = 400 mm, (e) L = 500 mm, and (f) L = 700 mm.

Figure 4

Flank wear in case of wiper inserts after (a) L = 100 mm, (b) L = 200 mm, (c) L = 300 mm, (d) L = 400 mm, (e) L = 500 mm, and (f) L = 700 mm.

Figure 5

Average (VB) and maximum (VB_max) flank wear for the conventional and wiper inserts for a range of machined lengths of AISI 4340.

Figure 6

Wear on the rake face of the inserts after L = 400 mm: (a) conventional insert and (b) wiper insert.

Figure 7

3D scanned surfaces and 2D profiles of the conventional insert before and after use (a) 3D surface contour of a new insert; (b) 3D surface contour of a used insert after L = 400 mm; (c) 2D profile of new insert and (d) 2D profile of a used insert after L = 400 mm.

Figure 8

3D scanned surfaces and 2D profiles of the wiper insert before and after use (a) 3D surface contour of a new insert; (b) 3D surface contour of a used insert after L = 400 mm; (c) 2D profile of new insert and (d) 2D profile of a used insert after L = 400 mm.

Figure 9

Comparison of the surface roughness for the conventional and wiper inserts at various machined lengths.

Figure 10

Comparison of the specific energy consumption for the conventional and wiper inserts for various machined lengths.

Figure 11

Comparison of the machining action and the geometry of the chip for the (a) conventional and (b) wiper inserts at the same depth of cut and feed.