The Research On The Laser Surface Strengthening Of Hydraulic Oil Cylinder

Due to the hydraulic oil cylinder’s work environment is hyperthermia andhumid.So,the surface of Hydraulic oil cylinder is easily to be corroded,worn. And thereparing work costs too much if we change all over the workpiece. Laser surfacestrengthening technology makes the partial repair possible.In this study,fiber laser and CO2laser were used to process the surface of the45steel.The Influence factors to the laser surface strengthening and appropriate Processparameters were studied. Meanwhlie, The XRD,SEM, microhardness, Corrosionresistance and wear resistance of the samples were detected.And the strengtheningmechanism of laser surface process was discussed.The surface of the samples after Laser quenching can be divided in to two parts:melting zone and heat affected zone. Both of them are composed of martensite,but thesize of the grain in the melting zone is coarser. After laser alloyed,the surface can bedivided in to three parts: alloying zone,transition zone and the heat affected zone. Thealloying zone is composed of cellular crystal,dentrite crystal and plane crystal because oftemperature gradient and the solidified velocity. Transition zone and the heat affected zoneare composed of martensite,retained austenite and pearlite.And higher power or fasterscanning speed can creat finer grain.The surface of the sanples can be divided intocladding layer, alloying layer and heat affected zone after the laser cladding.From thecladding layer to heat affected zone,the microstructure turns from equiaxial crystal to themartensite in heat affected zone.While,after WC powder was mixed into the alloypowder,WC distribute in the cladding layer symmetrically.The microhardness of the cladding layer is enhanced to as high as900HV. While thealloying layer’s microhardness reached550HV. Higher microhardness could be obtainedby increasing the scanning speed or the laser power.The wear resistance and the corrosion resistance of the surface after laser alloyingor laser cladding can be improved drastically. But in joined the WC of composite coating,corrosion resistance of the surface got a slight decline.And the corrosion resistance or wear resistance can be influenced greatly by the laser process parameters.