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The work is focused on evaluation of resistance of the welded joint made of supermartensitic 13Cr6Ni2.5Mo stainless steel to sulfide stress cracking. Testing method A and solution B in accordance with NACE TM 0177 were used. All the testing samples were ruptured in a very short time interval but welded joint samples were fractured primarily in the weld metal or in heat affected zone and not in the basic material. Material analysis of samples were made with use of a ZEISS NEOPHOT 32 light microscope and a JEOL 6490LV scanning electron microscope.

Based on dilatometric tests, the effect of various values of previous deformation on the kinetics of austenite transformations during the cooling of 100Cr6 steel has been studied. Dilatometric tests have been performed with the use of the optical dilatometric module of the plastometer Gleeble 3800. The obtained results were compared to metallographic analyses and hardness measurements HV30. Uniaxial compression deformations were chosen as follows: 0, 0.35, and 1; note that these are true (logarithmic) deformations. The highly important finding was the absence of bainite. In addition, it has been verified that with the increasing amount of deformation, there is a further shift in the pearlitic region to higher cooling rates. The previous deformation also affected the temperature martensite start, which decreased due to deformation. The deformation value of 1 also shifted the critical cooling rate required for martensite formation from the 12 °C/s to 25 °C/s.

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The objective of investigation was to determine the influence of chosen cooling rates after finish rolling on final microstructural and mechanical properties of the laboratory rolled products from steel 42CrMo4. Metallographic analysis showed that microstructure of rolled products, which were after finish rolling cooled down in accelerated manner by water sprays, was composed mostly by hardening phases and by smaller amount of ferrite. Microstructure of the rolled product cooled down in furnace in decelerated manner was formed by pearlitic blocks with minority occurrence of ferrite. Laboratory rolled products cooled down by more complicated modes, which consisted of combination of their cooling by water sprays with subsequent annealing in furnace, showed different phase morphology and distinct band structure. Results of tensile test have proved that the applied modes of cooling of rolled products by accelerated manner had only very small influence on their final mechanical properties. Considerably cooling the rolled product by decelerated manner in furnace resulted in drop yield strength, but on the other hand in an increase of ductility. More complicated modes of cooling the rolled products, which comprised also their annealing, showed the possibilities of significant influencing the strength, and particularly the plastic properties of the steel 42CrMo4.

SummaryPure AISI 316L steel is investigated after solution heat treatment (1050 °C/H 2 O) and structural sensitization (650 °C). Two quite different intergranular corrosion tests are used to determine the degree of structural sensitization due to the precipitation of secondary phases along the grain boundaries (mainly the M 23 C 6 and σ-phase): the oxalic acid etch test and the electrochemical potentio-kinetic reactivation test. Generally, the dissolution of chromium-rich carbides (M 23 C 6 ) is provoked by oxalic acid etch tests, whereas the chromiumdepleted zones, in the vicinity of chromium-rich carbides (M 23 C 6 ), are attacked by electrochemical potentio-kinetic reactivation tests. Both intergranular corrosion tests are used to determine the maximum degree of structural sensitization. Thus structural analysis by carbon replicas reveals the Laves phase, and both the M 23 C 6 and (Cr,Mo) x (Fe,Ni) y phases. The results of intergranular corrosion tests are related to the findings of the structural analysis.

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