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Nowadays, Ni-Resist austenitic cast irons are widely used in industry. Because of the high amount of nickel (about 30 wt%), the production cost of these cast irons is high. This study aims to reduce the amount of nickel in these cast irons while increasing the amount of manganese. Manganese is well known for its ability to stabilize the austenite phase like nickel; it is also less expensive than nickel. After preparing as-cast iron samples, scanning electron microscopy was utilized to evaluate the microstructural characteristics of the samples. Microstructural observations showed increasing manganese and decreasing nickel caused the formation of LTF regions. Also, the mechanical behavior of specimens revealed that adding equal amounts of nickel and manganese simultaneously improves the strength and flexibility; however, adding 15 wt% manganese, causes the formation of Mn7C3. As for the final stage, electrochemical results obtained by potentiodynamic polarization analysis showed substituting nickel with manganese did not worsen corrosion resistance. [ABSTRACT FROM AUTHOR]

Pistons are mainly made of Al-Si alloys. The first piston channel's highly loaded diesel engines use a ring carrier. In this case, two different materials (aluminum alloy and austenitic cast iron) must establish an excellent metallic bond (intermetallic bonding layer). If no intermetallic bonding layer is formed, the first piston ring carriers will separate, and the engine will fail. This research is aimed at analyzing the formation of the intermetallic bonding layer. The manuscript presents an analysis of the formation of the metal connection between a piston and a ring carrier. The metallographic investigation combined an optical microscope with SEM/EDS to analyze the quality of the metal connection. The test results show the formation of the metal connection between the two materials of different qualities. [ABSTRACT FROM AUTHOR]

Wear and corrosion resistant austenitic cast irons were prepared by powder metallurgy (P/M). In this system, equivalent Mn were doped to replace nickel with a constant Nieq (the Ni equivalent number) to reduce the cost. Conventional high nickel cast iron was employed as a reference in this study. The hardness, dry sliding wear behavior and corrosion behavior of conventional and P/M cast iron were investigated under the same conditions. The result demonstrates that a little difference in hardness is found between Mn0-C (Mn-0wt% prepared by cast) and Mn0-PM (Mn-0wt% prepared by P/M). However, the wear resistance of Mn0-PM is better than Mn0-C due to the evenly distributed lubricating graphite. The wear resistance of P/M cast iron increases with the increase of Mn content which is attributed to the increased hardness. The corrosion behaviors for all the materials tested by using potentiodynamic polarization curves and electrochemical impedance spectroscopy (EIS) are almost the same, largely due to the formation of austenite matrix. Thereinto, Mn5-PM holds the best corrosion behavior with the lowest corrosion current density and highest polarization resistance. Because the potential difference between matrix and carbide is lower than that between matrix and graphite. The decreased graphite with the increased carbide induces a strong corrosion resistance in Mn5-PM.

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.

The paper presents influence of soaking parameters (temperature and time) on structure and mechanical properties of spheroidal graphite nickel-manganese-copper cast iron, containing: 7.2% Ni, 2.6% Mn and 2.4% Cu. Raw castings showed austenitic structure and relatively low hardness (150 HBW) guaranteeing their good machinability. Heat treatment consisted in soaking the castings within 400 to 600°C for 2 to 10 hours followed by air-cooling. In most cases, soaking caused changes in structure and, in consequence, an increase of hardness in comparison to raw castings. The highest hardness and tensile strength was obtained after soaking at 550°C for 6 hours. At the same time, decrease of the parameters related to plasticity of cast iron (elongation and impact strength) was observed. This resulted from the fact that, in these conditions, the largest fraction of fine-acicular ferrite with relatively high hardness (490 HV0.1) was created in the matrix. At lower temperatures and after shorter soaking times, hardness and tensile strength were lower because of smaller degree of austenite transformation. At higher temperatures and after longer soaking times, fine-dispersive ferrite was produced. That resulted in slightly lower material hardness.

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. [ABSTRACT FROM AUTHOR]

In the paper, a relationship between chemical composition of Ni-Mn-Cu cast iron and its structure, hardness and corrosion resistance is determined. The examinations showed a decrease of thermodynamic stability of austenite together with decreasing nickel equivalent value, in cast iron solidifying according to both the stable and the metastable systems. As a result of increasing degree of austenite transformation, the created martensite caused a significant hardness increase, accompanied by small decline of corrosion resistance. It was found at the same time that solidification way of the alloy and its matrix structure affect corrosion resistance to a much smaller extent than the nickel equivalent value, in particular concentration of elements with high electrochemical potential.

Within the presented work, the effect of austenite transformation on abrasive wear as well as on rate and nature of corrosive destruction of spheroidal Ni-Mn-Cu cast iron was determined. Cast iron contained: 3.1÷3.4 %C, 2.1÷2.3 %Si, 2.3÷3.3 %Mn, 2.3÷2.5 %Cu and 4.8÷9.3 %Ni. At a higher degree of austenite transformation in the alloys with nickel equivalent below 16.0%, abrasive wear resistance was significantly higher. Examinations of the corrosion resistance were carried out with the use of gravimetric and potentiodynamic method. It was shown that higher degree of austenite transformation results in significantly higher abrasive wear resistance and slightly higher corrosion rate, as determined by the gravimetric method. However, results of potentiodynamic examinations showed creation of a smaller number of deep pinholes, which is a favourable phenomenon from the viewpoint of corrosion resistance.

A new efficient method of casting tubular billets by directional solidification without the use of a core is proposed making it possible to obtain a fine-grained dense structure of cast iron due to intensive onesided heat removal and excess supply to the solidification front of superheated liquid phase during the entire billet formation time in a metal water-cooled mold (crystallizer). It is shown that the method makes it possible to obtain a prescribed final cast iron structure by creating a certain cooling regime for castings outside the mold. In the positive effect of directional solidification of the melt inherited by iron a decisive role is played by the formation of a dense structure and a more dispersed carbide eutectic with a favorable carbide morphology, which determines the good cast iron wear resistance. The results of studies confirm that the new casting method provides production of workpieces with a prescribed phase composition and improved physical, mechanical, and operating properties. The effect is considered of various factors of the formation of workpieces from different types of cast iron: gray alloyed with lamellar graphite, high-strength and high-chromium, and also Niresist cast iron, on the structure, properties and service life of components for critical purposes of general, mining and oil refining engineering. [ABSTRACT FROM AUTHOR]

In the research, relationships between matrix structure and hardness of high-quality Ni-Mn-Cu cast iron containing nodular graphite and nickel equivalent value were determined. Nickel equivalent values were dependent on chemical composition and differences between them resulted mostly from nickel concentration in individual alloys. Chemical compositions of the alloys were selected to obtain, in raw condition, austenitic and austenitic-martensitic cast iron. Next, stability of matrix of raw castings was determined by dilatometric tests. The results made it possible to determine influence of nickel equivalent on martensite transformation start and finish temperatures. [ABSTRACT FROM AUTHOR]

Influence of heat treatment parameters on abrasive wear and corrosion resistance of nodular cast iron Ni–Mn–Cu was examined. Chemical composition was selected in such a way, that austenitic matrix was obtained in raw castings (relatively good machinability). Heat treatment, consisting of soaking (450, 550, 650 °C for 4, 8, 12 h) and air cooling, led to partial transformation of austenite. At the lowest temperature, martensite was formed. Raising the temperature and prolonging the soaking time caused increase of austenite transformation degree. At the same time, a gradual change in morphology of the coniferous phase was observed in the direction of fine-acicular ferrite found in bainite or ausferrite. As a result, significant increase in hardness and wear resistance of castings was observed. The heat treatment caused slight changes in gravimetric corrosion rate. However, potentiodynamic studies indicate, that the nature of corrosion from local to uniform was changed. From the point of view of corrosion resistance, this is a very beneficial phenomenon. [ABSTRACT FROM AUTHOR]

The performed research was aimed at determining thermodynamic stability of structures of Ni-Mn-Cu cast iron castings. Examined were 35 alloys. The castings were tempered at 900 °C for 2 hours. Two cooling speeds were used: furnace-cooling and water-cooling. In the alloys with the nickel equivalent value less than 20,0 %, partial transition of austenite to martensite took place. The austenite decomposition ratio and the related growth of hardness was higher for smaller nickel equivalent value and was clearly larger in annealed castings than in hardened ones. Obtaining thermodynamically stable structure of castings requires larger than 20,0 % value of the nickel equivalent.

The results of studying the microstructure and microhardness of Ni-resist cast iron ChN16D7GKh after laser melt injection by means of introducing titanium particles into the melt are presented. The treatment was performed using a fiber laser with a beam focused into a spot 0.2 mm in diameter with a radiation power of 1 kW and the motion velocity of the laser beam of 10-40 mm/s. Titanium is dissolved in the cast-iron melt, and TiC particles are formed in the structure upon cooling. The coefficient of using the titanium powder increases as the fusion zone size increases and reaches 50% in the best case. A modified layer has a composite structure with a metallic matrix and a comparatively uniform distribution of titanium carbide particles. The microhardness of the modified zone is 600-700 HV. Its further growth is suppressed by the partial removal of carbon from the melt zone in the composition of red fume evolved in the process. Therefore, the Laves phase (TiFe) is formed instead of an increase in the TiC content upon increasing the titanium supply. The experimental data on the regularities of the weight loss caused by the substance removal from the melt zone depending on laser melting parameters are presented. [ABSTRACT FROM AUTHOR]

This paper presents the results of investigating an Al-Fin bond between an aluminum piston alloy and austenitic cast iron. The part investigated utilized an austenitic cast iron insert for the first ring groove for application in a highly loaded diesel engine for increased wear resistance. A metallographic investigation using an optical microscope in combination with SEMIEDS (Scanning Electron Microscopy/Energy Dispersive Spectroscopy) analysis and 3D visualization of the quality of the intermetallic bonding layer was performed. The test results show that a metallic bond can be formed between the aluminum piston alloy and the austenitic cast iron. [ABSTRACT FROM AUTHOR]

Laboratory experiments were conducted on the erosion-corrosion resistance of four groups of austenitic cast iron with different nickel contents under different acidic slurry conditions. The experiments involved measuring weight loss, examining corrosion morphology as well as X-ray diffraction analysis and electrochemical techniques. While the results showed little erosion-corrosion in a base sand particles environment, erosion-corrosion increased progressively with additions of HCl solution. With the presence of H+, intergranular corrosion and pitting attacks were centred at the boundaries of graphite flakes and alloy carbides. The electrochemical tests showed that the enrichment of nickel and copper in low Ni austenite cast iron can increase the corrosion potential to some extent. As a result, the low Ni cast iron in which Ni content is 8·36 wt-%, and Mn content is 6·57 wt-% exhibited better corrosion resistance than other low Ni cast irons and demonstrated comparable performance with high Ni austenite cast iron. [ABSTRACT FROM AUTHOR]

Examined was the influence of chemical composition defined by the nickel equivalent, as well as time and temperature of soaking on course of decomposition process of metallic matrix in the austenitic Ni-Mn-Cu cast iron. In alloys with the equivalent value ranging from 16.0% to 23.0%, with properly selected heat-treatment parameters, possible is controlled, partial transition of austenite to hard acicular ferrite. Obtained is the structure morphologically corresponding to that of ausferrite, characteristic for cast iron quench-hardened with isothermal transformation (e.g. CGI or ADI). Replacing the quench-hardening operation by soaking permits, among others, obtaining homogeneous structure in the entire cross-section of solid thick-walled castings or elimination of quenching stresses. [ABSTRACT FROM AUTHOR]

The performed research was aimed at determining thermodynamic stability of structures of Ni-Mn-Cu cast iron castings. Examined were 35 alloys. The castings were tempered at 900 °C for 2 hours. Two cooling speeds were used: furnace-cooling and water-cooling. In the alloys with the nickel equivalent value less than 20,0%, partial transition of austenite to martensite took place. The austenite decomposition ratio and the related growth of hardness was higher for smaller nickel equivalent value and was clearly larger in annealed castings than in hardened ones. Obtaining thermodynamically stable structure of castings requires larger than 20,0% value of the nickel equivalent. [ABSTRACT FROM AUTHOR]

Determined was quantitative effect of nickel equivalent value on austenite decomposition degree during cooling-down castings of Ni-Mn-Cu cast iron. Chemical composition of the alloy was 1.8 to 5.0 % C, 1.3 to 3.0 % Si, 3.1 to 7.7 % Ni, 0.4 to 6.3 % Mn, 0.1 to 4.9 % Cu, 0.14 to 0.16 % P and 0.03 to 0.04 % S. Analysed were castings with representative wall thickness 10, 15 and 20 mm. Scope of the examination comprised chemical analysis (including WDS), microscopic observations (optical and scanning microscopy, image analyser), as well as Brinell hardness and HV microhardness measurements of structural components. [ABSTRACT FROM AUTHOR]

Determined were direction and intensity of influence of alloying additions on the number of eutectic graphite colonies in austenitic cast iron Ni-Mn-Cu. Chemical composition of the cast iron was 1.7 to 3.3% C, 1.4 to 3.1% Si, 2.8 to 9.9% Ni, 0.4 to 7.7% Mn, 0 to 4.6% Cu, 0.14 to 0.16% P and 0.03 to 0.04% S. Analysed were structures of mottled (20 castings) and grey (20 castings) cast iron. Obtained were regression equations determining influence intensity of individual components on the number of graphite colonies per 1 cm² (LK). It was found that, in spite of high total content of alloying elements in the examined cast iron, the element that mainly decides the LK value is carbon, like in a plain cast iron. [ABSTRACT FROM AUTHOR]

Results of a study on influence of Cr, Mo and Al on the microstructure, abrasive wear and corrosion resistance of Ni-Mn-Cu cast iron in the as-cast and heat-treated conditions are presented. Because of the chilling effect of first two elements (tendency to create hard spots), graphitising Al was added to the alloys, with the highest concentration of Cr and Mo. All castings in the as-cast condition showed an austenitic matrix, guaranteeing good machinability. Heat treatment of raw castings, consisting in annealing at 500 °C for 4 h, resulted in partial transformation of austenite. As a result the carbon-supersaturated acicular ferrite, morphologically similar to bainitic ferrite was formed. The degree of this transformation increased with increasing concentrations of Cr and Mo, which successively decreased the thermodynamic stability of austenite. A change of matrix structure made it possible to significantly increase hardness and abrasive-wear resistance of castings. The largest increment of hardness and abrasion resistance was demonstrated by the castings with the highest total concentration of Cr and Mo with an addition of 0.4% Al. Introduction of Cr and Mo also resulted in an increase of corrosion resistance. In the heat-treated specimens, increasing the concentration of Cr and Mo resulted in a successive decrease of the depth of corrosion pits, with an increase in their number at the same time. This is very favourable from the viewpoint of corrosion resistance. [ABSTRACT FROM AUTHOR]