Influence of the surface finishing on electrochemical corrosion characteristics of AISI 316L stainless steel

Stainless steels from 316 group are very often and successfully uses for medical applications where the good mechanical and chemical properties in combination with non-toxicity of the material assure its safe and long term usage. Corrosion properties of AISI 361L stainless steel are strongly influenced by surface roughness and treatment of the engineering parts (specimens) and testing temperature. Electrochemical characteristics of ground, mechanically polished and passivated AISI 316L stainless steel specimens were examined with the aim to identify the polarization resistance evolution due to the surface roughness decrease. Results obtained on mechanically prepared specimens where only natural oxide layer created due to the exposure of the material to the corrosion environment was protecting the materials were compared to the passivated specimens with artificial oxide layer. Also the influence of temperature and stabilization time before measurement were taken into account when discussing the obtained results. Positive influence of decreasing surface roughness was obtained as well as increase of polarization resistance due to the chemical passivation of the surface. Increase of the testing temperature and short stabilization time of the specimen in the corrosion environment were observed negatively influencing corrosion resistance of AISI 316L stainless steel

Influence of the surface finishing on electrochemical corrosion characteristics of AISI 316L stainless steel

Stainless steels from 316 group are very often and successfully uses for medical applications where the good mechanical and chemical properties in combination with non-toxicity of the material assure its safe and long term usage. Corrosion properties of AISI 361L stainless steel are strongly influenced by surface roughness and treatment of the engineering parts (specimens) and testing temperature. Electrochemical characteristics of ground, mechanically polished and passivated AISI 316L stainless steel specimens were examined with the aim to identify the polarization resistance evolution due to the surface roughness decrease. Results obtained on mechanically prepared specimens where only natural oxide layer created due to the exposure of the material to the corrosion environment was protecting the materials were compared to the passivated specimens with artificial oxide layer. Also the influence of temperature and stabilization time before measurement were taken into account when discussing the obtained results. Positive influence of decreasing surface roughness was obtained as well as increase of polarization resistance due to the chemical passivation of the surface. Increase of the testing temperature and short stabilization time of the specimen in the corrosion environment were observed negatively influencing corrosion resistance of AISI 316L stainless steel

Prediction of maximum casting defect size in MAR-M-247 alloy processed by hot isostatic pressing

Nickel based MAR-M-247 superalloy treated by hot isostatic pressing was investigated with the aim to identify the influence of casting defect size on fatigue life. Two testing temperatures of 650 and 800°C and one stress amplitude were chosen for fatigue tests. The Murakami approach and the largest extreme value distribution theory were applied. It has been found that the maximum size of casting defects in a specimen can be satisfactorily predicted. Fatigue life of specimens was in the good agreement with assumptions based on the evaluation and prediction of the casting defect size

Prediction of maximum casting defect size in MAR-M-247 alloy processed by hot isostatic pressing

Nickel based MAR-M-247 superalloy treated by hot isostatic pressing was investigated with the aim to identify the influence of casting defect size on fatigue life. Two testing temperatures of 650 and 800°C and one stress amplitude were chosen for fatigue tests. The Murakami approach and the largest extreme value distribution theory were applied. It has been found that the maximum size of casting defects in a specimen can be satisfactorily predicted. Fatigue life of specimens was in the good agreement with assumptions based on the evaluation and prediction of the casting defect size

Influence of the surface finishing on the corrosion behaviour of AISI 316L stainless steel

The influence of the surface preparation of AISI 316L stainless steel by mechanical grinding, polishing and following passivation was examined by immersion corrosion tests in solution simulating body fluids. Decreasing of the surface roughness by finer preparation resulted in decrease of corrosion rates of AISI 316L stainless steel. Passivation of specimens resulted in decreasing of the corrosion rates and in decreasing of the corrosion process speed independently on the roughness of specimens before passivations. Lowest corrosion rates were observed in the case of polished and passivated specimens. However no significant difference in corrosion rates between polished and ground specimens with following passivation was observed

Effect of Quench Environment on the Conversion Coatings on Magnesium Alloy AZ91

The aim of the study is to achieve fine microstructure of AZ91, due to the optimized heat treatment processes, which can be easily coated with a normal conversion process as phosphating. Determination of the influence of the AZ91 microstructure, mainly precipitates which are created using different cooling media during the heat treatment and definition of the best heat treatment process parameters are the main experimental sections of the work. The structure of the samples heat treated under different conditions was subsequently compared with the structure of the as cast state of AZ91. The morphology of the conversion coating was studied by scanning electron microscopy (SEM) and amount of individual elements in the deposited coating was determined by EDS analysis

Influence of processing techniques on microstructure and mechanical properties of a biodegradable Mg-3Zn-2Ca alloy

New Mg-3Zn-2Ca magnesium alloy was prepared using different processing techniques: gravity casting as well as squeeze casting in liquid and semisolid states. Materials were further thermally treated; thermal treatment of the gravity cast alloy was additionally combined with the equal channel angular pressing (ECAP). Alloy processed by the squeeze casting in liquid as well as in semisolid state exhibit improved plasticity; the ECAP processing positively influenced both the tensile and compressive characteristics of the alloy. Applied heat treatment influenced the distribution and chemical composition of present intermetallic phases. Influence of particular processing techniques, heat treatment, and intermetallic phase distribution is thoroughly discussed in relation to mechanical behavior of presented alloys.Web of Science911art. no. 88