Effect of Aging Time and Boron Addition on the Properties of 9-12% Cr Power Plant Steels - outcomes from Different Experimental Investigations

The relation between the aging time and the mechanical properties of the investigated steels was demonstrated graphically as a result of an experimental work in this paper. The effect of trace boron in steels, especially the influence of boron on microstructure and properties of 9-12% Cr steels were also summarized. Three alloys with and without boron of 9% Cr steels were prepared. The specimens prepared for testing were aged at 20 oC and 650 oC for time range of 3000 to 10000 hrs. Concerning the effect of boron addition to the 9-12% Cr steels, some results of recent investigation studies by other researchers were also mentioned in this paper for more information about the role of this alloying element in improving of high alloyed chromium steels

Az anyagtudomány és a mechanika szerepe az anyagok és szerkezetek élettartam növelésében = Role of material science and mechanics in lifetime extension of materials and components

A kutatómunka során kifejlesztett, pontosított rúdmodell esetén meghatározásra került a Pasternak-féle ágyazás rugómerevségét. A rúdmodell a középsíkban repedéssel ellátott kompozit rudak rugóállandójára ad pontosított képletet. A különféle korrekciók vagy a próbatest vastagság menti, vagy annak csúsztató rugalmassági moduluszától függnek. A Pasternak-féle rugók esetén a merevség inkább a vastagság menti modulusszal hozható kapcsolatba. A rugók merevségét kombinált végeselem-analitikus módszerrel lett kiszámolva. Az un. DCB próbatestre egy olyan végeselem modellt lett szerkesztve, amelyben a csúsztató rugalmassági modulusz értékét végtelenhez tart. Ily módon kiküszöbölhető azok a hatások, amelyek a csúsztató rugalmassági modulusszal kapcsolatosak Ezután az analitikus modell eredményét egy konstans paraméter beállításával a végeselem modell eredményéhez lett igazítva. A számítást kis és nagy hajlító rugalmassági moduluszú, szén- és üvegszál erősítésű kompozit anyagokra is el lett végezve. Az említett konstans paraméter választott értéke minden esetben nagyon jól illeszkedett a végeselem eredményeihez. A Pasternak-féle rugók merevségének ismeretében a globális módszert még pontosabbá lett. A módszer előnye, hogy pontos és viszonylag egyszerű. | Using the previously developed refined beam model the stiffnes of the Pasternak foundation was determined. The beam model provides an improved compliance expression for delaminated composite beams. The different corrections of the compliance and the strain energy release rate depend on the shear and transverse modulus of the material. It was shown that the Pasternak foundation can be related to the transverse modulus. The stiffness of the Pasternak foundation was determined by a combined analytical-finite element method. This was carried out by using a special DCB specimen of which shear modulus tended to infinity. This way those effetcs, which are related to the shear modulus can be eliminated. Then the value of a constant parameter was chosen in order to reach the best agreement with the finite element model. The computation was performed even for high and low modulus glass and carbon fiber reinforced materials and it was found that the chosen value of the constant satisfies all the cases studied. Using the Pasternak foundation stiffness the global mode decomposition method was improved. The advantages of the method are that it is accurate and easy to apply

ПОВЕРХНОСТНОЕ ОПЛАВЛЕНИЕ БЫСТРОРЕЖУЩИХ СТАЛЕЙ ЭЛЕКТРОННЫМ ЛУЧОМ. Poverhnostnoe oplavlenie bystrorežuşih stalej elektronnym lučom

Observations аге reported оn structure transformations of high speed steels R6 and R 11 during the local impulse surface melting bу high energy electron bеаm. Тhе electron bеаm melting resulted in а fine dendritic structure and а vегу fine carbide network. This kind оf heat treatment retains muсh greater amounts of the alloying elements and сагbоп in solid solution then conventional quenching processes. Owing to this high solute supersaturation the carbides in the melted zone turned into М2С and а small amount of М6С and the austenite parameter rose. Тhе quantity of the retained austenite is higher than after quenching. Small quantity of b-fеггitе was detected nеаг the surface. It is ргоbаbу coused bу partial evaporation of сагbоn and the rapid cooling. Martensite "average" C-parameter and "average" tetragonality decreased. These structure transformations were also proved bу other authors to lead to higher strength аt elevated temperatures along with the tempering resistance of thе melted zone

МЕСТНОЕ ОПЛАВЛЕНИЕ ПОВЕРХНОСТИ ИНСТРУМЕНТАЛЬНЫХ СТАЛЕЙ ЭЛЕКТРОННЫМ ЛУЧОМ. 1.Ч. Mestnoe oplavlenie poverhnosti instrumental'nyh stalej ęlektronnym lučom. 1. č.

In this work the effect of local surface melting of high-speed steels by high-energy electron beam was investigated. As a result of local electron beam melting and rapid cooling the microstructure in the melted surface zone of high-speed tools steels turned into very fine dendritic structure with great number of fine carbides. The relative content of alloying elements in the melted zone increased, the distribution of elements were more homogeneous. In this case the toughness, the strength at elevated temperatures, the tempering resistance of the melted zone and the tool life increased. The observation in this work point out the secondary dendritic arm spacing (d) is dependent on cooling rate (v) at the solidification