Impacts of diamond particle sizes on performance of Ni-Cu superhydrophobic coatings on drilling tool surfaces

ObjectiveApplying superhydrophobic coatings on drilling tool surfaces can effectively alleviate the challenges posed by drill bit balling and core barrel blockage. However, the limited mechanical stability of superhydrophobic coatings has somewhat hindered their widespread application in practical operations. MethodsTo improve the durability of superhydrophobic coatings, this study co-deposited diamond micropowder into Ni-Cu composite coating using composite electrodeposition, followed by surface modification using 1H,1H,2H,2H-perfluorodecyltrimethoxysilane (PFDTES). Employing a variety of testing methods, this study investigated the impacts of the mass fractions of diamonds with particle sizes of 1 μm and 20 μm (also referred to as diamonds W1 and W20, respectively) on the surface morphology, roughness, superhydrophobicity, and superhydrophobic durability of the composite coatings. The chemical composition of the composite coatings was analyzed using energy-dispersive X-ray spectroscopy (EDS) and Fourier Transform Infrared (FTIR) spectroscopy, and erosion experiments on the coatings were carried out to explore their wear resistance. Results and ConclusionsThe results indicate that a high proportion of diamond W1 promoted the formation and evolution of cauliflower-like clusters, significantly enhancing the coatings’ superhydrophobicity. After fluorination modification of the coatings, the PFDTES molecules were successfully grafted onto their surfaces, effectively reducing their surface energy. The coatings containing only diamond W1 exhibited the optimal micro-nano hierarchical structure. These coatings delivered excellent superhydrophobic performance, with a contact angle reaching up to 159.3° ± 1.5° and a sliding angle of 0.5° ± 0.2°. The erosion experiments revealed that diamond W1 boosted the strength and hardness of cauliflower-like clusters, while diamond W20 protected the clusters (especially their sides) from direct wear by quartz sand. When the coatings contained 75% (mass fraction) diamond W1, diamonds with two particle sizes exhibited the optimal synergistic protection effects, with the coatings demonstrating excellent superhydrophobic durability and mud cake scaling resistance. The results of this study offer a practical solution to common issues encountered during drilling, such as drill bit balling and mud cake scaling on the internal walls of drilling tools, while also introducing new ideas for enhancing the durability of superhydrophobic coatings, thus holding significant potential for application.