Comparison on tribological properties between Cu coating and Ni-P coating on P110 oil tube steel substrate

Cu and Ni-P coatings on the P110 steel's substrate were deposited. The tribological properties of P110 substrate, Cu coating and Ni-P coating were comparatively investigated. The morphologies of the wear scar were analyzed by using scanning electron microscopy, energy dispersive spectroscopy and scanning tunneling microscopy and the wearing mechanism was discussed. The results show that the wear resistance of the two kinds of coatings was significantly improved as compared to that of P110 substrate. The wear resistance of Ni-P coating was better than that of Cu coating. The flaking pit was observed on the wear scar of P110 substrate, and the wear mechanisms were delamination and abrasive wear. In case of Cu coating, plastic deformation caused by adherent copper debris under compression was found on the wear scar and the wear mechanisms were fatigue and adhesive wear. The grooves on the wear scar of the Ni-P coating indicated mild abrasive wear.