In the present work there are given the results of experimental investigations of contact fatigue and the wear of deformable high strength ADI (DADI) class aluminum cast iron depending on the phase ratio in metallic matrix. It is shown that: Modification of cast iron melt with the magnesium vapor gives the opportunity the low silica (0.5-0.7% Si) high strength cast iron to be received, in which the concentration of sulfur will not exceed 0.002%. Besides, the type and degree of austenite transformation of the received cast iron can easily be varied so that required ratio of phase components such as upper bainite, lower bainite, martensite, carbide and the retained austenite could be provided in the metallic matrix and therefore the hardness in the range of 30-57HRC can be given. The wear rolling and rolling with creep tests carried out on the specimens tempered till different levels of hardness showed strong dependence of contact fatigue and the wear on the amount of retained austenite in the samples with optimal ratio, required for keeping the high wear resistance of wearing surfaces, of bainite and martensite phase components in the matrix structure. The stated parameters of the contact fatigue and the wear gives us reason to treat the high strength DADI class aluminum cast iron as an efficient substitute for the expensive steel as a constructional material for manufacturing the critical parts for high pressure multistep gas pumping compressors.
This work reports on the aluminization and oxidation behaviour of a new class of cast iron (Deformable Austempered Ductile Iron, DADI). The slurry aluminization resulted in uneven coatings due to the lack of wettability of molten aluminium to the graphite inclusions of the substrate. In spite of this, the isothermal tests at 650°C for 100h in air revealed a drastic reduction of oxygen uptake related to the formation of mixed Al-containing spinels compared to the very unprotective iron oxides formed in the absence of coating. It derives that deposition of thicker aluminide layers by precoating with e.g. nickel would be a promising way to protect further DADI cast iron.
Because of development of the deformed cast irons of bainitic-martensitic type, the investigation of influence of different thermal treatments on their structure, properties and destruction during the shock-dynamic load, is of considerable interest. The above alloys are prospective materials, mainly, for production of gears, crankshafts and other heavy-loaded elements. In the present work the hot-rolled at 900 o C cast irons, with the rates of deformation 20% and 40%, were studied. The following thermal treatments were applied: 1-austenization at 900 o C during 30 min. plus austempering at 400 o C or 270 o C; 2-austenization at 900 o C during 30min. plus water quenching with subsequent austempering at 400 o C or 270 o C. It has been established that the combination of different types of treatment makes it possible to control morphology and distribution of structural components of the cast iron in wide range. The impact strength of the cast iron is changing consequently. The influence of amount and stability of the retained, in the cast iron matrix, austenite on the destruction parameters is also discussed in this work. The influence of substructure of the hot-rolled austenite on the kinetics and the mechanism of structure transformations, at different types of thermal treatment, were studied as well.
Waste, generated during the industrial process negatively affects the environment, but at the same time it is a valuable raw material and can be used to produce new marketable products. The study of the effectiveness of Self-propagating High temperature Synthesis (SHS) methods, which are characterized by the simplicity of the necessary equipment, the purity of the final product and the high processing speed, is under the wide scientific and practical interest to solve the set problem. The work describes technological aspects of production of ferro boron by the method of SHS - metallurgy from iron-containing wastes of rolled production for alloying of cast iron and results of effect of alloying element on degree of boron assimilation with liquid cast iron. Features of Fe-B system combustion have been investigated and the main parameters to control the phase composition of synthesis products have been experimentally established. Effect of overloads on patterns of cast ligatures formation and mechanisms of structure formation of SHS products was studied. It has been shown that an increase in the content of hematite Fe2O3 in iron-containing waste leads to an increase in the content of phase FeB and accordingly, the amount of boron in the ligature. Boron content in ligature is within 3-14%, and phase composition of obtained ligatures consists of Fe2B and FeB phases. Depending on the initial composition of the wastes, the yield of the end product reaches 91 - 94%, and the extraction of boron is 70 - 88%. Combustion processes of high exothermic mixtures allow obtaining a wide range of boron-containing ligatures from industrial wastes. In view of the relatively low melting point of the obtained SHS-ligature, the positive dynamics of boron absorption by liquid iron is established. According to the obtained data, the degree of absorption of the ligature by alloying gray cast iron at 1450 ° C is 80 - 85%. When combined with the treatment of liquid cast iron with magnesium, followed by alloying with the developed ligature, boron losses are reduced by 5-7%. At that uniform distribution of boron micro-additives in volume of treated liquid metal is provided.
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