Abstract
Analysis of structure phase states and properties of the layers formed on HARDOX 450 low alloy steel by welded-on wires with boron content of 4.5 and 6.5 % wt. was made by the methods of modern physical material science. In the initial state HARDOX 450 steel has the structure of tempered martensite, in the volume and along the boundaries of crystals of it the cementite particles are located. The particles located in the volume have acicular shape and those along boundaries are mainly round. The presence of extinction bend contours has been revealed, indicative of the curvature torsion of crystal lattice of the material’s portion. They originate and finish on the interfaces of martensite crystals. Scalar density of chaotically located dislocations and forming the netlike substructure is 6.2·1010 cm–2. The layer welded on HARDOX 450 steel has microhardness increasing by more than two-fold that of the base. Analysis of state diagrams of Fe – C, Fe – B, B – C systems and polythermal cross–sections in Fe – C – B system has shown that the rapid cooling of Fe23C6 – Fe23B6 alloys from liquid state would facilitate the formation of multiphase structural states. It is stated by the methods of transmission electron diffraction microscopy that the reasons for the high microhardness level of the surface layers are the following: formation of iron borides and crystals of ultafine-dispersion (up to 100 nm) packet martensite with high level (~1011 cm–2 ) of scalar density of dislocations; presence of nanodimentional particles of iron and boron carbides in the volume and on the boundaries of martensite crystals; high level of curvature torsion of crystal lattice of iron borides and α-phase grains, caused by the internal stress fields along interphase (interface of iron boride crystals and α-phase grains) and intraphase boundaries (interface of iron borides and martensite crystals packet). Increase in boron concentration from 4.5 to 6.5 % is accompanied by the sufficient increase (by 1.2 – 1.5 times) in hardness of welded layer. It is caused by the increase of dimensions and relative content of iron boride regions by 1.5 – 2.0 times.
Highlights
Analysis of structure phase states and properties of the layers formed on HARDOX 450 low alloy steel by welded-on wires with boron content of 4.5 and 6.5 % wt. was made by the methods of mo dern physical material science
The layer welded on HARDOX 450 steel has microhardness increasing by more than two-fold that of the base
Analysis of state diagrams of Fe – C, Fe – B, B – C systems and polythermal cross–sections in Fe – C – B system has shown that the rapid cooling of Fe23C6 – Fe23B6 alloys from liquid state would facilitate the formation of multiphase structural states. It is stated by the methods of transmission electron diffraction microscopy that the reasons for the high microhardness level of the surface layers are the following: formation of iron borides and crystals of ultafine-dispersion packet martensite with high level (~1011 cm–2 ) of scalar density of dislocations; presence of nanodimentional particles of iron and boron carbides in the volume and on the boundaries of martensite crystals; high level of curvature torsion of crystal lattice of iron borides and α-phase grains, caused by the internal stress fields along interphase and intraphase boundaries
Summary
В качестве материала основы использовали сталь марки Хардокс 450, элементный состав которой следую щий: 0,19 – 0,26 % C; 0,70 % Si; 1,60 % Mn; 0,25 % Cr; 0,25 % Ni; 0,25 % Mo; 0,004 % B; 0,025 % P; 0,010 % S, остальное – железо (по массе). Формирование наплавленного слоя осуществляли проволоками, элементный состав которых приведен ниже:. Исследования фазового состава и дефектной субструктуры стали и наплавленного металла осуществляли методами просвечивающей дифракционной элект ронной микроскопии (метод тонких фольг) [4 – 6]. Вырезанных электроискровым методом из наплавленного металла (слой, расположенный на половине толщины наплавленного металла). Утонение вырезанных таким образом пластинок до толщины 100 – 200 нм (тонкая фольга, необходимая для анализа методами просвечивающей электронной дифракционной микроскопии) осуществляли распылением металла ионным пучком на установке «IonSlicer» (фирма изготовитель JEOL). Механические свойства наплавленного металла и стали: микротвердость (метод Виккерса), нагрузка на индентор 5 Н
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
