Improvement in the Wear Resistance under Dry Friction of Electrodeposited Fe-W Coatings through Heat Treatments

Abstract

The influence of the microstructural transformations upon heat treatments on the wear resistance of Fe-W coatings is studied. The coatings are electrodeposited from a glycolate-citrate plating bath with 24 at.% of W, and the wear resistance is investigated under dry friction conditions using ball-on-disc sliding tests. The samples were annealed in Ar atmosphere at different temperatures up to 800 °C. The microstructural transformations were studied by means of X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), and Electron Backscattered Diffraction (EBSD) technique. Except for the coating annealed at 800 °C, all the tested coatings suffered severe tribo-oxidation which resulted in the formation of deep cracks, i.e., ~15 μm in depth, within the wear track. The precipitation of the secondary phases, i.e., Fe2W and FeWO4, on the surface of the sample annealed at 800 °C increased the resistance to tribo-oxidation leading to wear tracks with an average depth of ~3 μm. Hence, the Fe-W coating annealed at 800 °C was characterized with a higher wear resistance resulting in a wear rate comparable to electrodeposited hard chromium coatings, i.e., 3 and 4 × 10−6 mm3/N m, respectively.

Nanocrystalline Electrodeposited Fe-W/Al2O3 Composites: Effect of Alumina Sub-microparticles on the Mechanical, Tribological, and Corrosion Properties

“…The lowest wear rate (1.8·10 −6 mm 3 N −1 m −1 ) was obtained for the sample with the highest particles concentration, which is an order of magnitude lower than that of pure Fe-W alloy matrix. It is also comparable to the wear rate of annealed Fe-W alloy and even electrodeposited hard chromium coatings tested by using a similar set-up and dry friction conditions applied (Mulone et al, 2019). Thus, in annealed Fe-W alloys the reduction in the tribooxidation was achieved mainly due to the phase transformation, that is, the formation of Fe 2 W and FeWO 4 hard phases which are not prone to oxidation.…”

In-situ TEM annealing of amorphous Fe-24at.%W coatings and the effect of crystallization on hardness

“…The formation of the FeWO 4 phase is thought to be favored by oxygen contamination in the Ar atmosphere. In fact, the formation of the FeWO 4 phase is mainly observed at the surface of the annealed Fe-24at.%W coatings [2]. Furthermore, the FeWO 4 phase is not observed when performing the annealing in vacuum [8].…”

“…The Fe-W coatings were electrodeposited from a Fe(III)-based glycolate-citrate electrolyte, and the deposition parameters were applied to obtain a Fe-W coating with 24 at.% of W. Details about the electrodeposition can be found in [7]. For the deposition of the samples, a three-electrode cell was used composed of (1) a copper sheet as working electrode, a (2) platinized titanium was used as a counter electrode and (3) a saturated Ag/AgCl/KCl reference electrode. Prior to performing Differential Scanning Calorimetry (DSC) and TEM analysis, the Fe-24at.%W coating was mechanically removed (stripped off) from the substrate.…”

“…A large fraction of zero solutions is present, which appear as white pixels. Such high fraction (* 50%) of zero solutions can be related to the amorphous phase which is retained after the heat treatment at 800°C [2] which cannot be indexed by EBSD technique. XRD results acquired with grazing incidence geometry from a Fe-24at.%W sample annealed at 800°C revealed that Fe 2 W is mostly formed in the proximity of the sample surface [2], which explains the low fraction of Fe 2 W phase included in the phase map (* 3%) shown in Fig.…”

“…Lately, electrodeposited Fe-based alloys have gained considerable attention as a sustainable alternative to coatings produced using environmentally hazardous processes such as hard chrome coatings [1][2][3]. Because of the excellent properties such as high hardness and high wear and corrosion resistance, hard chromium coatings are commonly applied in aerospace and automotive applications, among others [4].…”