Improving Tribological Performance Of316Stainless Steel By Surface Texturing And Nitriding Duplex Treatment

Austenitic stainless steel possesses the greatest usage and production instainless steel and exhibits attractive properties as excellent corrosion resistanceand processing performance. So, it is wide application in modern industry as oneof the important engineering material. However, it has some disadvantages, suchas low surface hardness, poor wear resistance and cannot be used to make theparts of overloading high-speed friction pair. Therefore, it has great significanceto improve the tribological performance and expand application areas ofaustenitic stainless. It was different with the traditional surface modificationtechnology, in this paper, electrochemical tests was conducted on it to obtainsurface texture by making use of the high sensitivity of austenitic stainless steelto pitting corrosion in Cl-environment. In order to improve more performanceof tribological, the samples which have surface texture were treated by plasmanitriding. And their tribological properties and wear mechanisms wereinvestigated respectively under dry sliding and wet sliding condition. Theexperimental results show as follows.1. Surface texture after electrochemical treatment(1).The surface texture can be fabricated on surface of the316stainless steelby using electrochemical treatment. It can be found that different concentrations of NaCl electrolyte affect the dimension of the texture.(2).Under the dry sliding condition, the samples with surface texture canstore wear debris and reduce friction at the beginning of the sliding. The texturegradually destroyed for the low wear resistance of the316stainless steel and themass loss of the samples was slightly less than the substrate in the end of sliding.So, the tribological properties did not increase dramatically under the dry slidingcondition. In dry sliding against GCr15and Si3N4, the wear mechanism of thetreated samples was adhesive wear combined with oxidation wear and abrasivewear.(3).Under the wet sliding condition, the friction coefficient and mass loss ofthe substrates were similar to it under dry sliding condition. The samples afterelectrochemical treatment in three concentrations (20%,15%,10%) NaClelectrolyte had good friction reduction, and the friction coefficient was below0.15in the whole process of sliding. Because the texture can store grease andprovide secondary source of lubrication, the mass loss of treated samples wasreduced evidently and the tribological performance greatly improved. In wetsliding against GCr15, the wear mechanism of treated samples was severeplastic deformation; in wet sliding against Si3N4, the wear mechanism wassevere plastic deformation associated with abrasive wear.2. Nitriding compound treatment(1).The samples with texture retained its original structure and dimensionsafter plasma nitriding. The nitriding layers consisted of ε, γ′, CrN and thethickness of it is45μm. The micro-hardness of the layer was1048HV0.1, whichwas higher than the substrate257HV0.1. (2).Under the dry sliding condition, the friction coefficient fluctuation of thesample after nitriding compound treatment was very little. The texture whichhad not been completely destroyed after nitriding in the end of sliding can storewear debris and reduce friction during the whole process. Comparing with thesamples untreated, the mass loss was reduced dramatically, so it effectivelyimproved the tribological properties under the dry sliding condition. In drysliding against GCr15, the wear mechanism of compound treated sample wasmicro cutting wear combined with oxidation wear; in dry sliding against Si3N4,the wear mechanism was adhesive wear associated with oxidation wear andabrasive wear.(3). Under the wet sliding condition, the friction coefficient was below0.13in the whole process of sliding, the texture after nitriding can also store greaseand provide secondary source of lubrication. Comparing with the texturedsamples, the mass loss further reduced after nitriding compound treatment. Inwet sliding against GCr15, the wear mechanism was severe plastic deformation;in wet sliding against Si3N4, it only occurred slight abrasion.