Results of a research on influence of chromium, molybdenum and aluminium on structure and selected mechanical properties of Ni-Mn-Cu cast iron in the as-cast and heat-treated conditions are presented. All raw castings showed austenitic matrix with relatively low hardness, making the material machinable. Additions of chromium and molybdenum resulted in higher inclination to hard spots. However, a small addition of aluminium slightly limited this tendency. Heat treatment consisting in soaking the castings at 500 °C for 4 h resulted in partial transformation of austenite to acicular, carbon-supersaturated ferrite, similar to the bainitic ferrite. A degree of this transformation depended not only on the nickel equivalent value (its lower value resulted in higher transformation degree), but also on concentrations of Cr and Mo (transformation degree increased with increasing total concentration of both elements). The castings with the highest hard spots degree showed the highest hardness, while hardness increase, caused by heat treatment, was the largest in the castings with the highest austenite transformation degree. Addition of Cr and Mo resulted in lower thermodynamic stability of austenite, so it appeared a favourable solution. For this reason, the castings containing the highest total amount of Cr and Mo with an addition of 0.4% Al (to reduce hard spots tendency) showed the highest tensile strength.

A mathematical model of austenite - bainite transformation in austempered ductile cast iron has been presented. The model is based on a model developed by Bhadeshia [1, 2] for modelling the bainitic transformation in high-silicon steels with inhibited carbide precipitation. A computer program has been developed that calculates the incubation time, the transformation time at a preset temperature, the TTT diagram and carbon content in unreacted austenite as a function of temperature. Additionally, the program has been provided with a module calculating the free energy of austenite and ferrite as well as the maximum driving force of transformation. Model validation was based on the experimental research and literature data. Experimental studies included the determination of austenite grain size, plotting the TTT diagram and analysis of the effect of heat treatment parameters on the microstructure of ductile iron. The obtained results show a relatively good compatibility between the theoretical calculations and experimental studies. Using the developed program it was possible to examine the effect of austenite grain size on the rate of transformation.

Grey cast iron belongs to materials for casting production, which have wide application for different industry branches. Wide spectrum of

properties of these materials is given by the structure of base metal matrix, which can be influenced with heat treatment. Processes of

annealing can be applied for grey cast iron without problems. During heat treatment processes, where higher cooling rates are used, the

thermal and structural strains become important. Usage and conditions of such heat treatment for grey cast iron castings of common

production are the subject of evaluation of this article.

Within the presented research, effect of annealing on nature of corrosion damages of medium-nickel austenitic nodular cast iron castings,

containing 5.5% to 10.3% Ni, was determined. Concentration of nickel, lower than in the Ni-Resist cast iron, was compensated with

additions of other austenite-stabilising elements (manganese and copper). In consequence, raw castings with austenitic matrix structure and

gravimetrically measured corrosion resistance increasing along with nickel equivalent value EquNi were obtained. Annealing of raw

castings, aimed at obtaining nearly equilibrium structures, led to partial austenite-to-martensite transformation in the alloys with EquNi

value of ca. 16%. However, corrosion resistance of the annealed alloys did not decrease in comparison to raw castings. Annealing of

castings with EquNi value above 18% did not cause any structural changes, but resulted in higher corrosion resistance demonstrated by

smaller depth of corrosion pits.

In paper is presented technology of bimetallic layered castings based on founding method of layer coating directly in cast proces so-called method of mould cavity preparation. Prepared castings consist two fundamental parts i.e. bearing part and working part (layer). The bearing part of bimetallic layered casting is typical foundry material i.e. ferritic-pearlitic unalloyed cast steel, whereas working part (layer) is plate of austenitic alloy steel sort X2CrNi 18-9. The ratio of thickness between bearing and working part is 8:1. The aim of paper was assessed the quality of the joint between bearing and working part in dependence of pouring temperature and carbon concentration in cast steel. The quality of the joint in bimetallic layered castings was evaluated on the basis of ultrasonic non-destructive testing, structure and microhardness researches.

In paper is presented technology of bimetallic layered castings based on founding method of layer coating directly in cast process so-called method of mould cavity preparation. Prepared castings consist two fundamental parts i.e. bearing part and working part (layer). The bearing part of bimetallic layered casting is typical foundry material i.e. unalloyed cast steel, whereas working part is plate of austenitic alloy steel sort X2CrNi 18-9. The ratio of thickness between bearing and working part is 8:1. The aim of paper was assessed the quality of the joint between bearing and working part in dependence of pouring temperature and carbon concentration in cast steel. The quality of the joint in bimetallic layered castings was evaluated on the basis of ultrasonic non-destructive testing, structure and microhardness researches.

The mechanical behavior and the change of retained austenite of nanocrystalline Fe-Ni alloy have been investigated by considering the effect of various Ni addition amount. The nanocrystalline Fe-Ni alloy samples were rapidly fabricated by spark plasma sintering (SPS). The SPS is a well-known effective sintering process with an extremely short densification time not only to reach a theoretical density value but also to prevent a grain growth, which could result in a nanocrystalline structures. The effect of Ni addition on the compressive stress-strain behavior was analyzed. The variation of the volume fraction of retained austenite due to deformation was quantitatively measured by means of x-ray diffraction and microscope analyses. The strain-induced martensite transformation was observed in Fe-Ni alloy. The different amount of Ni influenced the rate of the strain-induced martensite transformation kinetics and resulted in the change of the work hardening during the compressive deformation.

The paper presents the effect of deformation temperature on the mechanical stability of retained austenite in a multiphase TRIP steel. Series of static tensile tests were carried out in the temperature range –20 to 140°C in order to simulate the temperatures occurring during stamping process of automotive steel sheets and conditions of their exploitation. Samples deformed at 20°C and 60°C showed the best combination of strength and ductility. It was related to the gradual transformation of retained austenite into martensite. Obtained results revealed that the intensity of TRIP effect is significantly related to the deformation temperature. The amount of retained austenite, which transformed into martensite during plastic deformation decreases as the deformation temperature increases. It was also found that the stability of retained austenite depends on its morphology. The obtained results showed the relationship between deformation temperature and the stability of retained austenite. The chemical composition and microstructure of multiphase steels dedicated to the automotive industry should be designed for providing the maximum TRIP effect at the specific deformation temperatures.

For the EN GX4CrNi13-4 martensitic stainless steel, research was conducted to investigate the impact of the quenching intensity and the content of nickel on the mechanical properties and amount of retained austenite. It was found that the amount of retained austenite significantly increases with growing nickel concentration. On the other hand, the cooling rate at quenching makes a difference only if the cooling is intensive, then amount of retained austenite decrease. A higher nickel content improves the mechanical properties. With more intensive cooling, the tensile strength decreases while the yield strength increases. The ductility is not significantly affected by the cooling intensity.

In this paper, the effect of changes the parameters of heat treatment on the structure and the degree of elements segregation was

determined, in the context of corrosion resistance of ductile iron Ni-Mn-Cu, containing 7.2% Ni, 2.6% Mn and 2.4% Cu. In the condition

after casting, castings of austenitic matrix and 160HBW hardness were obtained. The achieved castings were soaked at 450, 550 and

650°C for 4, 8 and 12 hours, then cooled down at the ambient air. In most cases, the heat treatment resulted in a change in the castings

matrix, had the consequence of increasing their hardness in comparison to raw castings. Increasing the temperature and prolonging soaking

time resulted in increasing the degree of transformation of austenite, while reducing the degree of elements segregation. This led to the

formation of slightly bigger number of pitting due to corrosion, but not so deep and more evenly distributed in comparison to raw castings.

Wherein the results of corrosion tests show that heat treatment of castings did not significantly change their corrosion resistance in

comparison to raw castings, in contrast to the significant increase in mechanical properties.

The modification is a widespread method of improving the strength properties of cast iron. The impact in terms of increasing amounts of

eutectic grains has been thoroughly studied while the issue of the impact on the mechanical properties of primary austenite grains has not

been studied in depth yet. The paper presents the study of both aspects. The methodology was to conduct the melting cast iron with flake

graphite, then modifying the alloy by two sets of modifiers: the commercial modifier, and a mixture of iron powder with a commercial

inoculant. The DAAS test was carried out to identify the primary austenite grains. The degree of supercooling was determined and the

UTS test was performed as well. Additionally carried out the metallographic specimen allowing for counting grains. It can be concluded

that the introduction of the iron powder significantly improved the number of austenite primary grains which resulted in an increase

in tensile strength UTS.

The results of the modification of austenitic matrix in cast high-manganese steel containing 11÷19% Mn with additions of Cr, Ni and Ti

were discussed. The introduction of carbide-forming alloying elements to this cast steel leads to the formation in matrix of stable complex

carbide phases, which effectively increase the abrasive wear resistance in a mixture of SiC and water. The starting material used in tests

was a cast Hadfield steel containing 11% Mn and 1.34% C. The results presented in the article show significant improvement in abrasive

wear resistance and hardness owing to the structure modification with additions of Cr and Ti.