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.
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.
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