Study On Tribological Properties Of Plasma Boridedand Mo-B Surfacealloyed316Stainless Steels

As an important engineering material, AISI316austenitic stainless steelhas a comprehensive and good overall performance, such as, beautifulappearance, excellent corrosion resistance, good ductility and toughness.Therefore it has a wide range of applications and development prospects inmarine, chemical, food, aerospace, chemical, medical, automotive and otherareas. However, the defects of low hardness and poor wear resistance, especiallysusceptible to adhesive wear, greatly limit the application of austenitic stainlesssteel. Surface alloying technique is considered to be an effective way to solvethis problem. Double glow plasma surface alloying (DG-PSA) technology isconsidered to be an effective way to solve this problem, which has a lot ofadvantages of energy conservation, environmental safety, simplicity, highinfiltration efficiency.Early research has shown that forming a hard modified layer on the surface of austenitic stainless steel can improve its tribological properties. Boronizing,as a stainless steel surface modification method, has raised a research upsurgedue to its high hardness, high wear resistance, especially the good resistance toadhesive wear and abrasive wear performance.In this paper, boriding modified layer and Mo-B composite layer wereprepared on the surface of316austenitic stainless steel by using double glowplasma surface alloying technology. The microstructure, compositiondistribution, phase structure and micro-hardness of modified layers wereanalyzed. We focused on friction and wear performance of boriding and Mo-Bmodified layers as well as the mechanisms of wear under the dry slidingconditions. The following conclusions were drawn:(1) Two modified layers with uniform, dense, continuous, gradientcomposition distribution were found on the surface of AISI316stainless steelafter double glow plasma surface boronizing and Mo-B duplex treatment. Thethicknesses of two modified layers were about8μm and23μm, respectively. Belement had the highest content in the surface of modified layers, and had agradient distribution from surface to interior. The boronized modified layer wasmainly composed of FeB and Fe2B, and Mo-B modified layer was made up ofFeB, Fe2B, Mo2B and FeMo2B2. The surface hardness of the two treated sampleswas about4times and4.5times as harder as the matrix. Scratch test results withno peeling off in the treated samples, showed that there was a good bondingstrength between matrix and modified layers. (2) Under the condition of dry friction, treated samples were slided withGCr15balls under the loads of1N,2N and5N, the correspondent averagefriction coefficients and wear rates were much less than the stainless steelsubstrate of untreated. To some extent, the tribological performances wereimproved. Especially, when the loads were1N and2N, wear resistance ofboronized samples were more outstanding. Compared with boriding, theabrasion resistance of samples after Mo-B treatment was higher when the loadwas5N.(3) When Mo-B sample grinded with Al2O3ceramic balls in three loads,the average friction coefficient were greater than the untreated stainless steelsubstrate. Under the loads2N and5N, the tribological performance wasimproved. When the load reached10N, the film with poor wear resistance wasworn out.(4) In dry sliding against GCr15and Al2O3, the wear mechanism of316stainless steel substrate sample was abrasive wear and adhesive wear, While theboronized and Mo-B composite treated samples was the micro-abrasive wear,and were accompanied by a small amount of adhesive wear.