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Abstract: The influence of surface mechanical attrition treatment (SMAT) on pack boronizing of AISI 304 stainless steel (304 SS) is addressed. SMAT of 304 SS was performed using 8mm Ø 316L stainless steel balls for 60min. Untreated and SMATed 304 SS samples were pack boronized by single stage (at 1223K for 1, 3 5 and 7h) and duplex (973K for 1h and 1223K for 1h) treatments. SMATed 304 SS increased the kinetics of boron diffusion, enabled the formation of a higher volume fraction of alloy borides and increased the hardness of the borided layer. Duplex treatment increased the case depth than the single stage treatment. The findings of this study suggest that SMAT can be used as an effective pretreatment for boronizing of 304 SS. [Copyright &y& Elsevier]

This work examines the role of counterface materials on the tribological behaviour of Mg alloys subjected to plasma electrolytic oxidation (PEO) process and focuses on reducing the sliding coefficient of friction (COF) values of PEO treated surfaces. Surfaces of AZ31 grade Mg alloy were subjected to a PEO treatment in a sodium metasilicate and potassium hydroxide containing electrolyte. Unlubricated sliding wear tests were conducted using counterfaces made of nitride based (N-based), TiN, TiCN, CrN and hydrogenated diamond-like carbon (H-DLC) coated as well as uncoated SAE 52100 grade bearing steel balls. MgO based coatings formed on the surfaces of samples during PEO process increased the wear resistance of AZ31, regardless of the type of counterface material used. Sliding the PEO treated surfaces against counterfaces made of uncoated steel and N-based coatings yielded high COF values of 0.6–0.8 that exceeded those of the uncoated AZ31 against the same counterfaces. During dry sliding of H-DLC counterface on the MgO coating, smooth and stable friction curves with a low steady state COF value of 0.13, were recorded. Therefore, a major drawback of PEO treatment that gives rise to surfaces with high COF could be addressed by running them against H-DLC coated counterfaces, a method that could be applied to development lightweight tribological components that are both sliding wear resistant and have low COF. • Plasma electrolytic oxidation (PEO) coated AZ31 showed low wear but high friction. • The counterface had a significant effect on the friction behaviour of PEO coating. • TiN, TiCN, and CrN showed high coefficient of friction (COF) of 0.6–0.8 against PEO. • Hydrogenated diamond-like carbon (H-DLC) reduced COF of PEO to 0.13. [ABSTRACT FROM AUTHOR]

This paper explores the effects of atmosphere on the tribological behavior of MoS 2 coatings deposited on the AISI304 steel using magnetron sputtering. The wear resistance and corresponding failure mechanisms were evaluated. The results show that both the friction coefficient and wear coefficient increase as the vacuum degree increases. The introduction of oxygen and H 2 O into the background vacuum environment significantly promotes the formation of transfer films, and results in the disorder of the crystal orientation and defect introduction in MoS 2 , which will strengthen the adhesive interactions between 52100 steel bearing ball and transfer films, and then leads to the prolongation of the wear life of the MoS 2 coatings. • The MoS 2 coatings deposited by magnetron supttering display a better tribolgical performance under nitrogen than vacuum. • Under vacuum, the tribological performance for MoS 2 coating is poor with few transfer film observed. • Under oxidizing atmosphere, the transfer film is visible, and the friction coefficient is rather low. • A small amount of oxidizing gas can improve the adhesion strength between transfer film and tribo-pair. [ABSTRACT FROM AUTHOR]