Wear behaviour of nanocrystallised Hadfield steel

A thick nanocrystalline surface layer with gradient nanostructure was produced on Hadfield steel through high-speed pounding (HSP) for 240 min. The grain sizes in the surface layer decreased to about 25 nm. To study the wear behaviour of the nanocrystallised Hadfield steel, three types of samples (a nanocrystallised sample (NS), an untreated sample (US) and a deformed sample (DS) had the same hardness as NS) were studied by using a pin-on-disc type tribometer under un-lubricated conditions at 25 degrees C, 300 degrees C, and 500 degrees C. The experimental results show that the coefficient of friction and wear weight loss of the NS are lower than for the DS and the US and that the wear resistance is remarkably improved. Compared with the US, the enhanced wear properties of the NS must be attributed to the increased hardness, which improves the resistance to plastic deformation and wear removal. However, compared with the DS, after surface nanocrystallisation of the NS, a transition occurs in the dominant wear mechanism from adhesive wear to slight abrasive wear. Therefore, the advantages realised in the wear properties of the NS may be attributed to the enhancement of the surface activity by grain nanocrystallisation, which results in improvements in the formation of the oxide layer. The roughness of the worn surfaces shows that both the wear scar width and depth of the worn surface of the NS are much smaller than those found in the DS and the US. Finally, a wear model of nanocrystallised material was established. (C) 2012 Elsevier 13.V. All rights reservect