____ : ..... '"i-t.-

Degradation mechanisms in martensitic stainless steels: Wear, corrosion and tribocorrosion appraisal

Surface properties of nitrided layer on AISI 316L austenitic stainless steel produced by high temperature plasma nitriding in short time

Wear and wear-induced debris is a significant factor in causing failure in implants. Reducing contact pressure by using a textured surface between the femoral head and acetabular cup is crucial to improving the implant’s life. This study presented the effect of surface texturing as dimples on the wear evolution of total hip arthroplasty. It was implemented by developing finite element analysis from the prediction model without dimples and with bottom profile dimples of flat, drill, and ball types. Simulations were carried out by performing 3D physiological loading of the hip joint under normal walking conditions. A geometry update was initiated based on the patient’s daily routine activities. Our results showed that the addition of dimples reduced contact pressure and wear. The bottom profile dimples of the ball type had the best ability to reduce wear relative to the other types, reducing cumulative linear wear by 24.3% and cumulative volumetric wear by 31% compared to no dimples. The findings demonstrated that surface texturing with appropriate dimple bottom geometry on a bearing surface is able to extend the lifetime of hip implants.

The Effect of Bottom Profile Dimples on the Femoral Head on Wear in Metal-on-Metal Total Hip Arthroplasty.

Validity of “sputtering and re-condensation” model in active screen cage plasma nitriding process

AISI 420 martensitic stainless steel was treated by active screen plasma nitriding. The test table was placed inside the steel screen but isolated from the cathodic potential. The specimens, together with the furnace wall and test table, were earthed, resulting in formation of anodic potential. Treatments were carried out in NH3 atmosphere of 400 Pa for 6 h at temperature ranging from 440 to 520 °C. The specimens were characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and micro-hardness measurement. The results showed that anodic nitriding treatments were able to produce different types of modified surface layers at different temperatures. The thickness of the nitrided layers and surface roughness increased with the nitriding temperature. Dry sliding wear tests and electrochemical corrosion tests were conducted on the untreated substrate and nitrided specimens. It can be concluded that active screen plasma nitriding at anodic potential improved the hardness, wear resistance, and corrosion properties of AISI 420 stainless steel.

Wear and corrosion properties of AISI 420 martensitic stainless steel treated by active screen plasma nitriding

Numerical optimization of the groove texture bottom profile for thrust bearings

The effect of surface nanocrystallization on plasma nitriding behaviour of AISI 4140 steel

Plasma nitriding experiments were carried out with pulsed dc glow discharge plasma in ammonia atmosphere at temperatures ranging from 450 to 540 °C for 4 h. In this process, the AISI 316L austenitic stainless steel samples were set on a plate at anodic potential. The phase composition, the thickness and morphology of the nitrided layer, as well as its surface hardness, were investigated using X-ray diffraction, glancing angle X-ray diffraction, optical microscopy, scanning electron microscopy and microhardness tester. The results showed that the microstructure and phase composition depended on the nitriding temperatures. In particular, a nitrided layer consisting of 3-layered structure was formed on the sample nitrided at 510 and 540 °C. The surface microhardness values and the thickness of the hardened layers increased as the nitriding temperature increased. In addition, the corrosion and wear properties of the untreated and nitrided samples were evaluated. The results showed that anodic plasma nitriding of austenitic stainless steel was a suitable process for improving the surface hardness and wear resistance properties without deteriorating corrosion resistance.

Yang Li

Papers

Surface properties of nitrided layer on AISI 316L austenitic stainless steel produced by high temperature plasma nitriding in short time

Wear and corrosion properties of AISI 420 martensitic stainless steel treated by active screen plasma nitriding

Numerical optimization of the groove texture bottom profile for thrust bearings

The effect of surface nanocrystallization on plasma nitriding behaviour of AISI 4140 steel

Plasma nitriding of AISI 316L austenitic stainless steels at anodic potential