Corrosion testing of sa 387 gr. 91 steel

Corrosion behaviour of steel Sa 387 Gr. 91 is tested in solutions containing chloride and sulphate anions. These solutions simulate the conditions of marine and industrial atmosphere. The tests are carried out in a slightly acidic and moderately acidic environment. It is shown that the steel corrodes uniformly without pitting or other forms of local dissolution. Corrosion current density is determined by three independent electrochemical techniques (linear polarization resistance, electrochemical impedance spectroscopy and linear sweep voltammetry). Values of corrosion rate are calculated based on values of corrosion current density. Values of corrosion rate obtained by different electrochemical techniques are in a very good agreement. An estimation of the working life of a pressure vessel made of steel Sa 387 Gr. 91 is given from the standpoint of general (uniform) corrosion

Corrosion testing of sa 387 gr. 91 steel

Corrosion behaviour of steel Sa 387 Gr. 91 is tested in solutions containing chloride and sulphate anions. These solutions simulate the conditions of marine and industrial atmosphere. The tests are carried out in a slightly acidic and moderately acidic environment. It is shown that the steel corrodes uniformly without pitting or other forms of local dissolution. Corrosion current density is determined by three independent electrochemical techniques (linear polarization resistance, electrochemical impedance spectroscopy and linear sweep voltammetry). Values of corrosion rate are calculated based on values of corrosion current density. Values of corrosion rate obtained by different electrochemical techniques are in a very good agreement. An estimation of the working life of a pressure vessel made of steel Sa 387 Gr. 91 is given from the standpoint of general (uniform) corrosion

Microstructural and basic mechanical characteristics of ZA27 alloy-based nanocomposites synthesized by mechanical milling and compocasting

Particulate nanocomposites with the base of ZA27 alloy were synthesized using an innovative route, which includes mechanical milling and compocasting. Scrap from the matrix alloy and ceramic nanoreinforcements were mechanically milled using the ball-milling technique, which led to the formation of composite microparticles. The use of these particles in the compocasting process provided better wettability of ceramic nanoreinforcements in the semi-solid metal matrix, which resulted in a relatively good dispersion of the nanoreinforcements in nanocomposite castings. The presence of nanoreinforcements led to the grain refinement in the matrix of nanocomposites. The mechanical properties of the synthesized nanocomposites are improved and compared with the properties of the metal matrix. The observed increase in the hardness of nanocomposites with Al2O3 nanoreinforcements (20-30 nm) was 6.5% to 10.8%, while the yield strength of these nanocomposites has increased by 12.2% to 23.2%. The hardness and compressive yield strength of the nanocomposites with Al2O3 nanoparticles (100 nm) increased by 1.7% to 8.0% and 2.3% to 8.3%, respectively. The increase in hardness of the nanocomposites with SiC nanoparticles (50 nm) was 11.5% to 20.6%, while the increase in the yield strength was 15.6% to 24.5%. The greatest contribution to the overall strengthening in the synthesized nanocomposites is the result of increased dislocation density due to the difference in coefficients of thermal expansion for the matrix alloy and nanoreinforcements

Microstructural and basic mechanical characteristics of ZA27 alloy-based nanocomposites synthesized by mechanical milling and compocasting

Particulate nanocomposites with the base of ZA27 alloy were synthesized using an innovative route, which includes mechanical milling and compocasting. Scrap from the matrix alloy and ceramic nanoreinforcements were mechanically milled using the ball-milling technique, which led to the formation of composite microparticles. The use of these particles in the compocasting process provided better wettability of ceramic nanoreinforcements in the semi-solid metal matrix, which resulted in a relatively good dispersion of the nanoreinforcements in nanocomposite castings. The presence of nanoreinforcements led to the grain refinement in the matrix of nanocomposites. The mechanical properties of the synthesized nanocomposites are improved and compared with the properties of the metal matrix. The observed increase in the hardness of nanocomposites with Al2O3 nanoreinforcements (20–30 nm) was 6.5% to 10.8%, while the yield strength of these nanocomposites has increased by 12.2% to 23.2%. The hardness and compressive yield strength of the nanocomposites with Al2O3 nanoparticles (100 nm) increased by 1.7% to 8.0% and 2.3% to 8.3%, respectively. The increase in hardness of the nanocomposites with SiC nanoparticles (50 nm) was 11.5% to 20.6%, while the increase in the yield strength was 15.6% to 24.5%. The greatest contribution to the overall strengthening in the synthesized nanocomposites is the result of increased dislocation density due to the difference in coefficients of thermal expansion for the matrix alloy and nanoreinforcements. © The Author(s) 2018