Tribological behavior of Inconel 718 alloy when cutting with a carbide insert prepared using the SPS technique under dry and lubricated sliding conditions

Abstract

The paper presents the results of the wear mechanisms research of uncoated cutting inserts of tungsten carbides (WC) without Co matrix made by the SPS technique in finish turning Inconel 718. The tests were performed with the application of coolant/lubrication and in dry condition. Moreover, morphology of the obtained chips was evaluated, as well as the topography of the machined surface. The coefficient of the chip shortening and the frequency of the chip vibration during machining were also determined. For the inserts used in the test, the friction coefficient, µ, has also been determined. Significant differences in the wear of the tool flank face for various feed speeds where the dominating sign was abrasive wear and oxidation. It has been found that the dominating mechanism of the wear of the rake face was adhesion of the material under machining whose surface exceeded beyond the field of the chip cross section regardless of value of feed and machining conditions (machining with cooling or without cooling). SEM analysis has shown that, in addition to adhesion, the major symptom of wear at lower feed values was delamination of the inserts; at higher feeds the major symptom of wear was chipping growing with the increase of feed. Machining with SPS inserts without the cooling and lubricating liquid has generated surfaces with lower average values of the roughness heights, Sa. It has been found that the chip shortening coefficient depends on the conditions of cooling/lubrication and that it decreases with the increase of the feed. The chip vibration frequency shows higher values in dry machining.