Coated tool inserts with crater-like surface topography last longer

Abstract

This paper presents the result of an investigation into the performance of Tungsten Carbide tool Grade –K inserts coated with titanium nitride (TiN). The TiN coating was done by physical vapour deposition process. Comparative cutting tests using control specimens coated with TiN having plain surface structures and tests specimens /inserts with crater-like surface topography. The surface roughness was created by electrical discharge machining (EDM) which generated an undulating surface roughness of 1.5 microns on the tools’ rake face. This level of surface roughness was determined at earlier experiments. In both cases, the inserts were coated with TiN to a thickness of 4µm. The machining tests were carried out on Mild Steel grade EN-3 (AISI -1045_200Bhn). Various cutting speeds, up to an increase of 40% of the conventional tool manufacturer’s recommended speed of 250 m/min were investigated. Thirty cuts (passes) were carried out for each inserts at the speeds investigated. After every five passes, microscopic pictures of the tool wear profiles were taken in order to monitor the progressive wear on the rake face and, on the flank of the insert. The power load was monitored for each cut using an on board meter on the CNC Lathe machine. Results obtained confirmed advantages of cutting at all speeds investigated using coated inserts with crater-like surface topographies in terms of reduced tool wear. It is therefore concluded, that TiN coated EDMed inserts with crater-like surface structure if coated with TiN performs considerably better than the plain inserts and lasts longer.

Keywords: Coating, Titanium Nitride, Tool Life, Wear, Cutting, Tribology.