The studies of scale surface produced on outer diffusion layers

In this study at attempt was made to examine the scale formed on ferritic-austenitic duplex type steel subjected to previous thermochemical treatment. The treatment consisted in diffusion aluminising in a metallising mixture composed of Fe-Al powder. As an activator, ammonium chloride (NH4Cl) added in an amount of 2 wt.% was used. Then, both the base material and samples with the diffusiondeposited surface layers were oxidised at 1000°C in the air. Thus formed scales were identified by light microscopy, SEM and X-ray phase analysis. The aim of the oxidation tests carried out under isothermal conditions was to compare the scale morphology when obtained on untreated substrate material and on the surface layers rich in aluminium

Characteristics of centrifugally cast GX25CrNiSi18-9 steel

The paper presents the results of microstructural examinations of the industrial heat-resistant centrifugally cast GX25CrNiSi18-9 steel characterised by increased content of Cu. The study included changes in the microstructure of base cast steel respective of the steel held at a temperature of 900 and 950°C for 48 hours. Based on the results obtained, an increase in microhardness of the examined cast steel matrix with increasing temperature was stated, which was probably caused by fine precipitates enriched in Cr, Mo, and C forming inside the matrix grains.The layer of scale formed on the tested cast steel oxidised in the atmosphere of air at 900 and 950°C was characterised by an increased tendency to degradation with increasing temperature of the conducted tests

Effect of temperature on the mechanical properties of X5CrNi18-9 steel

The results of static tensile tests conducted on a selected steel grade with austenitic matrix are discussed in this paper. The tensile tests were carried out at the following temperatures: 200°, 400° and 700 °C. Under the conditions of the static tensile test, all the samples failed with a characteristic “necking” forming a cup-conical shape. It has been found that with increasing temperature the strength properties decrease and the elongation increases. The microscopic examinations of the fractures showed that they were mostly plastic, and numerous “dimples” were filled with non-metallic inclusions characterized by a globular shape and a size of up to 8 µm

Effect of freezing on abrasion resistance of cast steel containing 1,1 % C, 16 % Cr, and 0,9 % Mo

The results of abrasion-resistance tests that were carried out on cast steel containing 1,1 % C, 16 % Cr, and 0,89 % Mo after several variants of heat treatment (including freeze hardening at -70 °C immediately before tempering at 200° and 550 °C) are presented in this paper. The wear-resistance tests were carried out with the ball-on-disc dryfriction method. In the samples that were tempered at 200 °C (with and without freezing), lower mass losses were obtained than in the samples that were tempered at 550 °C. Additionally, it was found that the applied freezing procedure significantly contributed to the reduction of mass losses in those samples that were tempered at both temperatures

Effect of freezing on abrasion resistance of cast steel containing 1,1 % C, 16 % Cr, and 0,9 % Mo

The results of abrasion-resistance tests that were carried out on cast steel containing 1,1 % C, 16 % Cr, and 0,89 % Mo after several variants of heat treatment (including freeze hardening at -70 °C immediately before tempering at 200° and 550 °C) are presented in this paper. The wear-resistance tests were carried out with the ball-on-disc dryfriction method. In the samples that were tempered at 200 °C (with and without freezing), lower mass losses were obtained than in the samples that were tempered at 550 °C. Additionally, it was found that the applied freezing procedure significantly contributed to the reduction of mass losses in those samples that were tempered at both temperatures

Characteristics of low nickel ferritic-austenitic corrosion resistant cast steel

The article presents the results of microscopic examinations of corrosion resistant cast steel with reduced nickel content obtained in a test casting with varying wall thickness. Investigations were carried out in as-cast condition and after heat treatment. Regardless of the casting wall thickness, increasing the manganese and nitrogen content to about 5 % and 2 500 ppm, respectively, yields the material with a two-phase microstructure containing ferrite in an amount of 55,6 ÷ 57,2 % (magnetic method) and 52,3 ÷ 55,2 % (analytical method). Based on the results of metallographic examinations, total elimination of the secondary austenite from the microstructure was observed. Microhardness measurements showed average values of 352,3 μHV20 and 267 μHV20 for the chromium ferrite and austenite, respectively

Influence of the cooling rate on the corrosion resistance of duplex cast steel

The results of the influence of the cooling rate of the casting made of the acid-resistant ferritic - austenitic cast steel on the microstructure and corrosion resistance are presented in the paper. Samples cut out from the walls of the casting being cooled at the cooling rate of 3,2 - 0,5 ºC/s were used in the study. Different cooling rates create favorable conditions for the segregation processes lowering properties of castings. It was found, that differences in the polarization curves occur only in the more aggressive corrosive environment. The reason of such behaviour of cast steel is the segregation of elements dissolved in austenite and the difference in the volume fraction of ferrite and austenite in the walls of the different thickness

Effect of high-manganese cast steel strain hardening on the abrasion wear resistance in a mixture of SiC and water

The study attempts to determine the impact of the high-manganese cast steel strain hardening on its abrasion wear resistance in a mixture of SiC and water prepared in accordance with ASTM G75. For tests, the high-manganese cast steel containing 10.7, 17.9 and 20.02% Mn was selected. The results of microstructure examinations and abrasion wear resistance tests carried out on the material in non-hardened condition and after strain hardening with a force of 539.55kN were disclosed. Additionally, the surface of samples after a 16-hour cycle of abrasion tests was examined. Moreover, based on the obtained results, the effect of different contents of Mn in cast steel was studied, mainly in terms of its impact on the abrasion wear resistance. The results obtained on the tested materials were compared with the results obtained on the low-alloyed abrasion wear-resistant cast steel L35GSM