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Abstract

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.
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Authors and Affiliations

D. Medyński
A. Janus
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Abstract

A research of wear resistance of an austenitic cast iron with higher resistance to abrasive-wear and maintained corrosion resistance characteristic for Ni-Resist cast iron is presented. For the examination, structure of raw castings was first formed by proper selection of chemical composition (to make machining possible). Next, a heat treatment was applied (annealing at 550 °C for 4 hours followed by air cooling) in order to increase abrasive-wear resistance. One of the factors deciding intensity of wear appeared to be the chilling degree of castings. However, with respect to unfavourable influence of chilling on machining properties, an important factor increasing abrasivewear resistance is transformation of austenite to acicular ferrite as a result of annealing non-chilled castings. Heat treatment of non-chilled austenitic cast iron (EquNi > 16%) resulted in much higher abrasive-wear resistance in comparison to the alloy having pearlitic matrix at ambient temperature (EquNi 5.4÷6.8%).
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Authors and Affiliations

D. Medyński
A. Janus
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Abstract

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 resista

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Authors and Affiliations

A. Janus
D. Medyński
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Abstract

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.

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Authors and Affiliations

A. Janus
D. Medyński
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Abstract

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.

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Authors and Affiliations

A. Janus
D. Medyński
S. Zaborski
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Abstract

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.

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Authors and Affiliations

M. Stachowicz
A. Janus
D. Medyński
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Abstract

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.

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Authors and Affiliations

A. Janus
D. Medyński
J. Chęcmanowski

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