Search

The aim of this study is to explore the potential engineering application of a thermally grown chromium oxide scale on a ferritic stainless steel. The friction and wear behaviour of the oxide scale were investigated by scratch and pin-on-disk tests. The failure mechanisms of the oxide scale subjected to scratch tests under both progressive and constant loading were investigated. It shows that the oxide scale adheres well to the steel substrate and is in a ductile failure. The oxide scale leads to an increase in the coefficient of friction (COF) under different constant loads when compared to what occurs when there is no oxide scale in the scratch test. The pin-on-disk tribological tests show that the chromium oxide scale on the ferritic stainless steel causes abrasive wear of the high-speed steel (HSS) pin, but it enhances the wear resistance of the ferritic stainless steel disk. The COF is slightly lower when there is oxide scale on the disk which is different from that by the scratch test. The ferritic steel substrate fine wear particles generated during the dry sliding and the formation of new compound layers on the surface can stabilise the COF. The wear mechanism is proposed and the tribological properties of the thermally grown chromium oxide by the two techniques are discussed. • Scratch behaviour of stainless steel with a chromia scale by oxidation. • The chromia scale showed adhesion strength with a significant variation. • Two different wear was observed with a similar COF. • The ferritic stainless steel substrate powder-like particles play a role in COF. [ABSTRACT FROM AUTHOR]

The oxidation kinetics of ferritic stainless steel 430 was studied in dry and humid air at 1090 °C by Thermo Gravimetric Analysis (TGA). Different atmospheres and heating times were adopted for reheating to obtain different compositions and thickness of the oxide scale. Hot rolling was performed on a 2-high Hille 100 experimental rolling mill at various reductions. Oxide scale thickness and composition were analysed with optical microscopy (OM), scanning electron microscope (SEM) and X-ray diffraction (XRD). The surface profiles were examined by a digital microscope, and the topographic features of the thin oxide scale surface were examined with an atomic force microscope (AFM) before and after rolling. The oxide scale surface and steel/oxide interface roughness were measured after rolling. Inverse calculation of the coefficient of friction was employed to analyse and the effect of oxide scale on friction in hot rolling. The coefficient of friction depends not only on the thickness of the oxide scale, but also on its composition and surface topography before hot rolling. [ABSTRACT FROM AUTHOR]

The tribological behaviour of innovative TiO 2 nano-additive water-based lubricant on ferritic stainless steel (FSS) 445 was characterised on a ball-on-disk tribometer. Non-oxidised (clean) and pre-oxidised FSS 445 disks with original rough surfaces were both applied in the tribological tests at room temperature. The results show that the water-based nanolubricants with concentrations of 0.4–8.0 wt% TiO 2 can significantly reduce the coefficient of friction (COF) on the two types of disks. The 4.0 wt% TiO 2 lubricant exhibits optimal tribological properties, including the lowest COF and the strongest anti-wear ability on the applied balls under all lubrication conditions. The lubrication mechanisms are primarily ascribed to the formation of tribofilm and the ball-bearing effect of the TiO 2 nanoparticles, respectively, on the two different disks. [ABSTRACT FROM AUTHOR]

A ball-on-disk tribometer was employed to evaluate the lubrication performance and mechanisms of innovative TiO 2 nano-additive water-based lubricants. Two experimental methods were applied to determine the optimal mass fraction of TiO 2 . In the method I, lubricants were added onto the worn disk tracks at a predetermined time interval. In the method II, the disks were immersed in the lubricants continuously during the whole process of tribological tests. The results both indicate that the water-based lubricants can significantly reduce the coefficient of friction (COF). The 0.8 wt% TiO 2 lubricant demonstrates excellent tribological properties including the lowest COF and the strongest wear resistance under all lubrication conditions. The lubrication mechanisms are attributed to the rolling and mending effects of the TiO 2 nanoparticles. [ABSTRACT FROM AUTHOR]

In this paper, wear and friction behaviour of high-speed steel (HSS) and indefinite chill (IC) material for rolling a ferritic stainless steel were investigated on a tribometer. A disk specimen of the ferritic stainless steel-B445J1M was pre-oxidised at 1100 °C for 30 min, and then rotated against a pin at 500 °C for 30 min. The pin was made of HSS or IC material. It was found that the friction coefficient of the IC was lower than that of the HSS, but the mass loss of the HSS pin was less than that of the IC pin. The oxide scale of the disk was more easily worn out and attached on the HSS pin than that of the IC pin. [ABSTRACT FROM AUTHOR]