Chemical heterogeneity as a factor of improving the strength of steels manufactured by selective laser melting technology

Abstract

The aim of this paper was to establish the causes of the heterogeneity of the chemical composition of the metal obtained by the LC technology. The powdered raw material was made from a monolithic alloy, which was fused by the SLM, the initial raw material was a laboratory melting metal of a low-carbon chromium-manganese-nickel composition based on iron.
 To determine the distribution pattern of alloying chemical elements in the resulting powder, electron-microscopic images of thin sections were combined with X-ray analysis data on the cross-sections of the powder particles. As a result, it was found that transition (Mn, Ni) and heavy (Mo) metals are uniformly distributed over the powder particle cross-sections, and the mass fraction of silicon (Si) is uneven: in the center of the particles, it is several times larger in some cases. The revealed feature in the distribution of silicon is supposedly due to the formation of various forms of SiO4 upon the cooling of the formed particles.
 The internal structure of the manufactured powder is represented by the martensitic structure of stack morphology. After laser fusion, etched thin sections revealed traces of segregation heterogeneity in the form of a grid with cells of ~ 200 μm.

The current state of laser technologies in the field of functional coatings

“…1). Если материал имеет высокие показатели отражения, то на него предварительно наносится поглощающее лазерное излучение покрытие [3,4]. Главными преимуществами данного метода являются: возмож-Л ность воздействовать на объект локально (размеры лазерного пятна варьируются от 10 -1 до 10 мм), возможность подвергать термообработке труднодоступные места на деталях.…”

“…Данный процесс основан на лазерном селективном спекании (SLS). Технология DMD сосредоточена на создании деталей из металла путем его прямого нанесения [22]. Она является одной из перспективных.…”

Treatment of plasma coatings by laser remelting

“…High mechanical performance materials are used to create equipment for oil and gas extraction. Such important characteristics are, for example, wear resistance, strength and durability [1][2][3]. It is known that the best complex of mechanical and operational properties have such alloys as «natural composites» [2].…”

“…Such important characteristics are, for example, wear resistance, strength and durability [1][2][3]. It is known that the best complex of mechanical and operational properties have such alloys as «natural composites» [2]. Such a structure can be obtained using various modern technologies, such as mechanical alloying or powder and granulated metallurgy.…”

“…There are a number of techniques aimed at increasing both surface and volume strength of dust coatings. These include: surface melting, thermal and thermochemical treatment, solder impregnation and others [1][2][3]. The aim of the study is to determine how laser beam fusion technology affects the structure and properties of plasma eutectic coatings.…”