High temperature tribological behaviour of PVD coated tool steel and aluminium under dry and lubricated conditions

Abstract

Aluminium alloys are commonly used as lightweight materials in the automotive industry. This non-ferrous family of metallic alloys offers a high versatility of properties and designs. To reduce weight and improve safety, high strength-to-weight ratio alloys (e.g. 6XXX and 7XXX), are increasingly implemented in vehicles. However, these alloys exhibit low formability and experience considerable springback during cold forming, and are therefore hot formed. During forming, severe adhesion (i.e. galling) of aluminium onto the die surface takes place. This phenomenon has a detrimental effect on the surface properties, geometrical tolerances of the formed parts and maintenance of the dies. The effect of surface engineering as well as lubricant chemistry on galling has not been sufficiently investigated. Diamond-like carbon (DLC) and CrN physical vapour deposition (PVD) coated steel have been studied to reduce aluminium transfer. However, the interaction between lubricants and PVD coatings during hot forming of aluminium alloys is not yet fully understood. The present study thus aims to characterise the high temperature tribological behaviour of selected PVD coatings and lubricants during sliding against aluminium alloy. The objectives are to first select promising lubricant-coating combinations and then to study their tribological response in a high-temperature reciprocating friction and wear tester. Dry and lubricated tests were carried out at 300 °C using a commercial polymer lubricant. Tests using DLC, CrN, CrTiN, and CrAlN coated tool steel were compared to uncoated tool steel reference tests. The initial and worn test specimen surfaces were analysed with a 3-dimensional (3D) optical profiler, scanning electron microscope (SEM) and energy dispersive X-ray spectroscope (EDS) as to understand the wear mechanisms. The results showed formation of tribolayers in the contact zone, reducing both friction and wear. The stability of these layers highly depends on both the coatings’ roughness and chemical affinity towards aluminium. The DLC and CrN coatings combined with the polymer lubricant were the most effective in reducing aluminium transfer.

Nitriding Effect on the Tribological Performance of CrN-, AlTiN-, and CrN/AlTiN-Coated DIN 1.2367 Hot Work Tool Steel

“…However, when NC, NA, and NCA surfaces interact with alumina, this stage shifts to relatively large distances of up to 20 m ( Figure 6 b). Friction and wear changes that occur during the run-in stage are related to the changes in surface roughness, surface composition, microstructure, and third-body distribution depending on the tribosystem [ 32 , 33 , 34 ]. The mean values of surface roughness (R a ) were determined for the heat-treated and coated samples and are 0.031 ± 0.006 µm, 0.033 ± 0.007 µm, and 0.030 ± 0.006 µm for HC, HA and HCA, respectively.…”

A review of advances in tribology in 2020–2021

“…Decrozant-Triquenaux et al [790] studied the high temperature friction and wear behaviour of PVD coatings against aluminium under dry and lubricated reciprocating sliding conditions in a flat on flat contact configuration. In these studies, uncoated tool steel was used as reference and a warm forming polymer-based lubricant for lubrication during the tests.…”

Abrasion Resistance of Restorative Coatings for Crankshafts and Bearings in Agricultural Machinery

“…The sectors were bimetallic (steel -lead bronze) with electrochemical antifriction alloy ЕО92 based on lead from silicofluorohydrogen electrolyte with the following composition: lead silicofluoride (РbSiF 6 ) -100-150 g•l -1 ; tin silicofluoride (SnSiF 6 ) 20-30 g•l -1 ; copper silicofluoride (CuSi|F 6 ) -5-15 g•l -1 ; and silicofluorohydric acid (Н 2 SiF 6 ) up to pH of 0.5 (Decrozant-Triquenaux et al, 2021;Kučera and Aleš, 2017).…”