Mo/O原子比对大气环境下含氢碳膜摩擦学行为的影响研究OA

Traditional diamond-like carbon(DLC)films suffer from prolonged friction running-in stage,unstable atmospheric lubrication performance and accelerated interfacial oxidative wear,severely restricting their service application in precision bearing stainless steel parts.To break through the performance limitation of single-element doped DLC coatings,improve comprehensive tribological stability of composite modified DLC films,and clarify the undisclosed correlation between Mo/O atomic ratio,film microstructure evolution and interfacial friction wear mechanism,the work aims to explore the regulation law of the Mo/O atomic ratio on tribological properties and reveal an original interfacial cyclic deterioration mechanism.The 9Cr18 martensitic stainless steel substrate was sequentially treated with ethanol-acetone ultrasonic oil removal,ion bombardment cleaning and surface polishing to unify initial substrate roughness.Mo and O co-doped DLC films with six gradient Mo/O atomic ratios were fabricated by direct current pulse magnetron sputtering.Fixed sputtering power,pulse frequency,working air pressure and deposition duration were adopted,and Mo/O atomic ratio was accurately regulated only by adjusting the spatial distance between substrate samples,Mo target and oxygen auxiliary target without changing other process parameters.AFM and SEM-EDS were used to test surface roughness,cross-section morphology and elemental distribution.Raman spectroscopy and high-resolution TEM were applied to characterize carbon bond structure,graphitization degree and internal defect characteristics.Ball-on-disk friction-wear tests were implemented under room-temperature atmospheric environment,fixed normal load,rotating speed and friction stroke to obtain friction curve and wear rate data.Combined with first-principles density functional theory calculation,oxygen adsorption energy and molecular interfacial binding energy of molybdenum oxide phases were quantitatively simulated.Key comparative experimental data showed that with the rise of Mo/O atomic ratio,film island-like grain growth was optimized effectively,average surface roughness decreased from 4.53 nm to 1.32 nm,and Raman ID/IG ratio increased by 27.6%,which remarkably promoted amorphous carbon transformation and expanded sp2 carbon domain volume.Core novel findings were summarized as follows:high Mo/O ratio eliminated intra-film molybdenum oxide agglomeration defects and realized homogeneous element distribution.It also inhibited physical-chemical oxygen adsorption at friction contact interface in atmospheric environment.For tribological properties,the optimized sample shortened friction break-in period from 14 min to 2 min,reduced average friction coefficient from 0.19 to 0.05,and cut volumetric wear rate to the minimum value of 3.4×10-7 mm3/(N·m).Worn pair characterization proved that high Mo/O ratio accelerated uniform dispersion and interfacial transfer of sp2 carbon domains,forming dense,low-friction lubricating transfer film on GCr15 ball surface.First-principles simulation verified that MoOx compounds possessed high negative oxygen adsorption energy,which enabled spontaneous capture of atmospheric oxygen.This work proposes an original self-circulating degradation mechanism for low Mo/O ratio DLC films for the first time:low Mo/O ratio induces excessive Mo oxide phase precipitation,enhances oxygen adsorption capacity of film system,consumes metallic Mo active components and further reduces Mo/O atomic ratio,forming irreversible performance vicious cycle and triggering microstructure deterioration and tribological failure.By contrast,appropriately increased Mo/O ratio suppresses oxide nucleation,promotes in-situ carbon graphitization and high-quality transfer film formation,synergistically optimizing friction state and anti-wear performance.The work provides novel mechanism support and process optimization strategy for tribological doped DLC coating design.