Original Article

Effect of Y₂O₃ content on microstructure and properties of Ni-based self-lubricating composite coating

¹ Schoolof New Energy and Materials, Southwest Petroleum University, Chengdu 610500 PR China
² Sichuan Provincial Engineering Research Center of Advanced Materials Manufacturing Technology for Shale Gas High-efficient Exploitation, Chengdu 610500, PR China
³ School of Robotics Engineering, Yangtze Normal University, Chongqing 408100, PR China

^* e-mail: hbslxp@163.com

Received: 17 April 2023
Accepted: 24 June 2023

Abstract

In order to improve the wear resistance and corrosion resistance of sucker rod surface, Ni-based self-lubricating composite coating with Y₂O₃ was successfully prepared on 35CrMo steel substrate by high frequency induction heating cladding technology. The coating structure is uniform and dense, and there are no obvious defects such as pores and cracks. The microstructure of the coating layer was studied by means of metallographic microscope, scanning electron microscope and X-ray diffractometer. The hardness, wear resistance and corrosion resistance of the coating layer were tested by microhardness testers, friction and wear testers and electrochemical workstations. The results show that the main phases of the composite coating are γ- (Ni, Fe), Ni3Fe, CrB, TiC and Cr₂₃C₆. When the addition amount of Y₂O₃ is 2%, the average microhardness of the composite coating is the highest, which is 805.1 HV_0.2; under the same wear conditions, the wear resistance of 2% Y₂O₃ composite coating is the best. The average friction coefficient and wear loss are reduced by 16.27% and 20.35% respectively compared with the composite coating without rare earth, and 37.55% and 48.02% respectively compared with the substrate. The wear mechanism of the composite coating is mainly severe adhesive wear, and there is a small amount of oxidation wear. With the increase of Y₂O₃ content, the self-corrosion potential of the composite coating fluctuates in a small range, and its self-corrosion current density decreases first and then increases. The self-corrosion potential of the composite coating containing 2% Y₂O₃ is more positive (–0.4316 V), and the self-corrosion current density is the smallest (3.9579 µA · cm⁻²), and its corrosion resistance is the best.