Load dependent microstructural evolution in an as-cast 26%Cr high chromium cast iron during unlubricated sliding

In the current study,an as-cast 26%Cr high chromium cast iron(HCCI)alloy was subjected to dry-sliding linear wear tests,under different loads.The loads were selected based on analytically computing the critical load(PC)i.e.,the load necessary to induce plastic deformation.The PC was calculated to be 15 N and accordingly,a sub-critical load(5 N)and an over-critical load(20 N)were chosen.The influence of increasing the load during the wear test was investigated in terms of the matrix microstructural behaviour and its ability to support the surrounding carbides.The morphological aspects of the wear tracks,and the deformed matrix microstructure adjacent and underneath the track was analysed by confocal laser scanning microscope(CLSM)and scanning electron microscope(SEM),respectively.No evidence of plastic deformation of the matrix was observed below PC.On the contrary,at loads equal to and higher than PC,the austenitic matrix plastically deformed as evidenced by the presence of slip bands.Electron backscattered diffraction(EBSD)measurements in terms of grain reference orientation deviation,and micro-Vickers hardness of the austenitic matrix indicated a deformation depth of about 40μm at the maximum applied load of 20 N.The active wear mechanisms during sliding were a combination of both adhesive and abrasive wear,although increasing the load shifted the dominant mechanism towards abrasion.This was primarily attributable to the increased propensity for carbide cracking and fracturing,combined with the inability of the hardened austenitic matrix surface and sub-surface to adequately support the broken carbide fragments.Moreover,the shift in the dominant wear mechanism was also reflected in the wear volume and subsequently,the wear rate.

Friction and wear behavior of carbon fiber reinforced lithium aluminosilicate composites sliding against GCr15 steel

Carbon fibers reinforced lithium aluminosilicate matrix composites(Cf/LAS)were prepared by slurry infiltration combined with a hot press procedure.The friction,wear behavior,and wear mechanisms of Cf/LAS composites under dry sliding conditions were investigated.The results show that the coefficient of friction(COF)initially increased with the increase in carbon fiber content,and reached the maximum value of 0.20 for the 33%Cf/LAS composite.The COF increased sharply with increasing sample temperature from RT to 300℃.The COF remained stable in the temperature range of 300–500℃.The two wear mechanisms of LAS glass-ceramics are fatigue wear and abrasive wear.The Cf/LAS composites demonstrate slight spalling and shallow scratches.These results show that carbon fibers improve the mechanical properties and wear resistance of Cf/LAS composites.