The Study Of Deep Cryogenic Treatment On Cemented Carbide YT15 And Ultrahigh Molecular Weight Polyethylene

Deep cryogenic treatment(DCT) refers to subjecting materials from room temperature to under -130℃at a controlled cooling rate,holding the materials at that temperature for a certain period and then followed by controlled heating back to room temperature.It can significantly improve the mechanical properties and wear performance of amount materials including of metals and non-metallic materials.It is easy to operate,non-polluting,low cost to provide the promising way to treat various materials.Cemented carbide YT15 with high hardness and wear performance has been widely used in the cutting industry.However,YT15 still can fail by wear or fracture.And ultrahigh molecular weight polyethylene (UHMWPE) has good wear performance and impact resistance,is used in various industries.However,there is still a low surface hardness,bending strength and abrasive wear performance.In the present study,YT15 and UHMWPE were treated by DCT,respectively.Untreated YT15 and UHMWPE were used as the control.Then the microstructure,mechanical properties,and wear performance of as-treated YT15 and UHMWPE were characterized and evaluated.The YT15 samples,which consists of 85WC-5Co-15TiC(wt%),were treated by deep cryogenic with(DCT+T) or without tempering(DCT) and untreated YT15(NT) as the control.Metallographic analysis,backscattered scanning electron microscope(BSEM),energy dispersive X-ray spectroscopy(EDX),and X-ray diffraction(XRD) were used to study the microstructure and surface residual stress of as-treated YT15.The hardness,bending strength,and fracture toughness of were tested.The contact angle and surface energy were determined. The dry sliding wear performance of as-treated YT15 was evaluated through reciprocating friction and ring-on-block wear model.The profiler was used to scan the cross-section of wear scar.Electronic balance was used weigh the weight loss of friction pair.The morphologies,elemental distributions,and wear mechanism of worn scar were characterized by means of SEM,SEM-EDX line analysis,and XRD.The results show that the relative amount and microstructure of main phases,includingα-phase,γ-phase,andη-phase of YT15 change after DCT or DCT+T.The surface residual compressive stress decreases significantly in DCT but is almost unchanged in DCT+T compared to that of NT.There are no significant differences in the Rockwell hardness of as-treated YT15.The Vickers hardness decreases but the bending strength and the fracture toughness increase in DCT and DCT+T.The surface energy decreases in DCT and DCT+T groups. DCT and DCT+T have significantly improved the wear performance of YT15. The wears of all three YT15 groups are caused mainly by abrasion followed by removal of theβ-phase and exposure of the WC.The UHMWPE samples were treated by deep cryogenic with(H+DCT) or without heat treatment(DCT) and untreated UHMWPE as the control.The crystallinity different treated was determined by Differential Scanning Calorimetry(DSC) and XRD.Fourier infrared was used to analyze the molecular structure.Tensile strength,compressive strength,microhardness,bending strength,and fracture toughness were tested.The dry sliding wear performance of as-treated UHMWPE was evaluated through pin disk wear model.The profiler was used to scan the cross-section of wear scar.The morphologies,elemental distributions,and wear mechanism of worn scar were characterized by means of SEM,SEM-EDX,and XRD.The results showed that the crystallinity,molecular structure,and strength of UHMWPE have no obvious change.The internal microhardness decreases greatly compared to that of surface and untreated samples.However,the toughness and wear resistance of UHMWPE increase significantly.The wears of all three UHMWPE groups are caused mainly by abrasion accompanied by plastic deformation.