Machining and Tribological Characterisation of Uncoated and Coated Carbide Inserts while Turning Tungsten Heavy Alloy.

Abstract

Tungsten heavy alloys are high density alloys containing 80 to 98 wt. % tungsten and a matrix made of relatively low melting elements such as copper, nickel and iron. These alloys are used as radiation shields, CG adjusters and also in armour piercing ammunition. These components essentially require machining to achieve the closer tolerance and finish. However, machining WHAs is challenging as it causes frequent cutting tool failure and surface damage. Hence, there is a need to come up with an appropriate selection of cutting tools and optimum cutting conditions that lead to economic and successful machining of WHAs. However, it is observed that the suitability of different grades of carbide inserts for machining WHAs are least explored. The present work, thus, focuses on the detailed study on three different commercially available cemented carbide inserts during turning operations of WHAs under both dry and wet cutting conditions. Three different feed rates have been used at a constant depth of cut and cutting speed. The best possible cemented carbide tooling solution for machining tungsten heavy alloys has been determined based on the surface finish obtained, chip geometry, cutting forces, and machining temperature. The observations made during machining are correlated to the tribological behavior of the inserts and the alloy from pin-on disc tests. Coated cemented carbide inserts provided surface roughness values lower than 1 μm under finish turning conditions. On the other hand, PVD coated inserts gave consistently better results over different feed rates and are found to experience lower tool wear for the specific cutting conditions. Additionally, an analytical model is used to predict the tool life under the given cutting conditions. The tool wear model also suggested better tool life for the PVD coated insert.
Subjects
TUNGSTEN alloys; MACHINING; IRON-nickel alloys; COPPER; CARBIDE cutting tools

Description