DLC and DLC-WS2 Coatings for Machining of Aluminium Alloys

Abstract

Machine-tool life is one limiting factor affecting productivity. The requirement for wear-resistant materials for cutting tools to increase their longevity is therefore critical. Titanium diboride (TiB2) coated cutting tools have been successfully employed for machining of AlSi alloys widely used in the automotive industry. This paper presents a methodological approach to improving the self-lubricating properties within the cutting zone of a tungsten carbide milling insert precoated with TiB2, thereby increasing the operational life of the tool. A unique hybrid Physical Vapor Deposition (PVD) system was used in this study, allowing diamond-like carbon (DLC) to be deposited by filtered cathodic vacuum arc (FCVA) while PVD magnetron sputtering was employed to deposit WS2. A series of ~100-nm monolayer DLC coatings were prepared at a negative bias voltage ranging between −50 and −200 V, along with multilayered DLC-WS2 coatings (total thickness ~500 nm) with varying number of layers (two to 24 in total). The wear rate of the coated milling inserts was investigated by measuring the flank wear during face milling of an Al-10Si. It was ascertained that employing monolayer DLC coating reduced the coated tool wear rate by ~85% compared to a TiB2 benchmark. Combining DLC with WS2 as a multilayered coating further improved tool life. The best tribological properties were found for a two-layer DLC-WS2 coating which decreased wear rate by ~75% compared to TiB2, with a measured coefficient of friction of 0.05.

Effect of Surface Modification via Laser Irradiation on the Operability of Carbide End Mills When Cutting Aircraft Alloys

“…In this case, the working edge is in conditions close to non-uniform all-round compression, which puts the metal in a more plastic state due to the increasing proportion of tangential stresses. At very high tensions, especially if they are accompanied by heating, deformation and plastic flow of the thin surface layer can be observed [16][17][18][19]. So for a cutting tool without contact plastic deformation to shear the required volumes of the machined material, the hardness of the tool material must significantly (more than 2.5 times) exceed the hardness of the machined material.…”

Effect of Poly Dimethyl Diallyl Ammonium Chloride‐Multiwalled Carbon Nanotubes Concentration on the Microstructure and Friction Behavior of Co‐Doped Diamond‐Like Carbon Films

“…[ 33 ] Based on the efforts of various researchers, doping different elements into DLC films to reduce the residual stress in the films and enhance the tribological properties of the films is one of the effective methods. It is strongly recommended that elements such as N, [ 34,35 ] B, [ 36 ] Ni, [ 37 ] Si, [ 38 ] Cr, [ 39 ] and Ti, [ 40 ] and compounds such as MoS 2 [ 41 ] and WS 2 [ 42 ] should be introduced into DLC films to improve the microstructure and properties of the films. Among them, Ni and N as doping elements can replace part of the H atoms in DLC films to reorganize the structure of the films, which preferred by researchers.…”

Operational properties of DLC coatings and their potential application

“…In industry, DLC coatings cover machine parts such as bearings, cylinders, pistons, gears, or mechanical seals [6,7]. They are also applied to the surface of cutting tools, injection molds, and various tribological pairs [8]. In consumer products, they can be found, among other things, on the surfaces of wristwatches (including bracelets and protective glass) or needles [9].…”