Surface engineering of timet 550 with oxygen to form a rutile-based, wear-resistant coating

Abstract

Recently, a thermal oxidation (TO) technique has been successfully developed and applied to the titanium alloy Ti-6Al-4V. This TO technique produces a thin, hard, rutile-based, wear-resistant coating on the surface of the titanium alloy, thus significantly improving the tribological properties of the titanium alloy. In the present investigation, the same principle has been applied to the ␣ ϩ ␤ highstrength titanium alloy Timet 550. A series of TO treatments have been carried out in air within the temperature range of 600 ЊC to 650 ЊC. This developed a rutile-based coating which greatly improved the tribological properties of Timet 550. Systematic characterization of the TO-treated surface was carried out using glow-discharge optical emission spectroscopy (GDS), X-ray diffraction (XRD), scanning electron microscopy (SEM), and high-resolution scanning electron microscopy (HR-SEM) techniques. Ball-on-disc friction testing was used to show the improvement in tribological properties for Timet 550 when TO treated. The sliding wear resistance of the TO treatment was investigated using an Amsler wear tester, utilizing a counterformal block-on-wheel configuration; the TO-treated Timet 550 was run against a carburized S156 steel with splash oil lubrication. It was found that the wear resistance of the TO-treated Timet 550 was greatly improved.

Surface modification of Ti–6Al–4V alloys using triode plasma oxidation treatments

“…Oxidation temperatures above 700°C can rapidly lead to oxide debonding because of the increased layer thickness which (as already described above) is associated with increased stress levels-but this can also be due to stratification of the oxide layer (together with increasing porosity) as the treatment time is lengthened [21]. Conversely, temperatures that are too low, say below around 500°C, do not provide the necessary activation energy for oxygen dissolution in the titanium lattice [13]. On the other hand, short treatment durations at higher temperatures may not produce a sufficiently thick oxide compound layer for an appreciable improvement in tribological properties [22].…”

“…These techniques include anodising [6], ion implantation [7], dc-diode plasma oxidation [8], plasma electrolytic oxidation [9], reactive dc-sputtering [10], vacuum heat treatment [11], thermal oxidation (TO) [12,13], oxygen-boost diffusion [14][15][16] and palladium-treated thermal oxidation [17,18]. Different techniques have each proved capable of producing thick oxide layers resilient to both chemical and mechanical attack.…”

“…However, thermal oxidation probably remains the leading technique for the treatment of titanium-since it readily produces thick, highly-crystalline rutile oxide films [18]. This process also has considerable commercial and environmental advantages, as it simply involves the heating of a component to a temperature between 450°C and 900°C in an oxygen-containing environment from, say, one hour up to many tens, or even hundreds of hours [13,19,20].…”

Oxidation of Ti–6Al–4V alloy

“…This surface modification technique, which benefits from the oxidation behaviour of titanium, is known as thermal oxidation. For titanium and its alloys, the ultimate goal of thermal oxidation is to create relatively thin, mechanically stable OL supported by the ODZ for successful surface protection at room temperature [8][9][10][11][12][13][14][15][16][17][18][19].…”

Guest editorial: In memory of Tom Bell

“…197,214,223 When combined with low friction surface coatings or modified layers, i.e. duplex surface treatments, it can produce titanium designer surfaces with low friction and high load bearing capacity, 113,114,155,162,224 which would pave the way to produce such highly loaded components as gears and bearings made from titanium alloys. …”