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Effect of plasma nitriding process conditions on corrosion resistance of 440B martensitic stainless steel

Łępicka M., Dahlke M.

Acta Mechanica et Automatica

2014

Vol. 8, no. 3

156--159

Martensitic stainless steels are used in a large number of various industrial applications, e.g. molds for plastic injections and glass moldings, automotive components, cutting tools, surgical and dental instruments. The improvement of their tribological and corrosion properties is a problem of high interest especially in medical applications, where patient safety becomes a priority. The paper covers findings from plasma nitrided AISI 440B (PN-EN or DIN X90CrMoV18) stainless steel corrosion resistance studies. Conventionally heat treated and plasma nitrided in N2:H2 reaction gas mixture (50:50, 65:35 and 80:20, respectively) in two different temperature ranges (380 or 450°C) specimens groups were examined. Microscopic observations and electrochemical corrosion tests were performed using a variety of analytical techniques. As obtained findings show, plasma nitriding of AISI 440B stainless steel, regardless of the process temperature, results in reduction of corrosion current density. Nevertheless, applying thermo-chemical process which requires exceeding temperature of about 400°C is not recommended due to increased risk of steel sensitization to intergranular and stress corrosion. According to the results, material ion nitrided in 450°C underwent leaching corrosion processes, which led to significant disproportion in chemical composition of the corroded and corrosion-free areas. The authors suggest further research into corrosion process of plasma nitrided materials and its degradation products.

Wyciskany film smarowy w stawie biodrowym z panewką porowatą

Krzemiński K., Rudniak L., Dahlke M.

Tribologia

2004

nr 1

45-62

W pracy przedstawiono wyniki badań wyciskanego filmu smarowego w stawie biodrowym z panewką porowatą. Ruch cieczy synowialnej w szczelinie smarowej opisano równaniem Reinoidsa, a w panwi porowatej równaniem Laplace'a. Przedstawione zostały przestrzenne rozkłady ciśnienia w szczelinie smarowej, wypadkowy wektor obciążenia, jego składowe stawu oraz położenie. Podano jak zmienia się rozkład ciśnienia w szczelinie smarowej stawu dla różnych wysokości szczeliny oraz dla różnych wartości przepuszczalności porowatej panwi. Określone zostały rozkłady prędkości cieczy synowialnej w szczelinie smarowej dla wyciskanego filmu smarowego. Do przeprowadzenia obliczeń wykorzystano program obliczeniowy FLUENT oparty o metodę elementów skończonych.

Analitycal research for squeezing out of synovial fluid in human hip joint has been presented in this paper. The fluid flow in joint gap was denoted by Reynolds equation and in porous bush by Laplace'a equation. The spherical pressure distributions in joint gap, resultand carrying force, its components, localization of result and load in human hip joints have been defined. Calculations of change pressure distributions in joint gap for variable height of joint gap and variable permeability of porous bush have been presented. The distributions of speed motions for squeezing out of synovial fluid in human hip joint was denoted. Calculation program FLUENT with finite elements metod to perform the calculations was applicated.