Research of chromosilicated coatings on compact powder steels

Microstructures, chemical and phase compositions of diffusion chromosilicated coatings on powder steels 20, 45, У8 and У10 are investigated. The presence of Cr23C6 and Cr7C3 phases with up to 0,25 % Si is shown in these coatings. The distribution of diffusing chemical elements over the depth of the coating and at the interface with the matrix base is studied. Keywords: diffusion, coating, microstructure, chromosilication, powder steel, corrosion resistance [email protected]

Investigation of the Microstructure of a Sintered Sample Obtained from Powder Steel X13

This article presents the results of a study of the microstructure of a sintered sample made of alloy X13 electroerosive materials obtained in butyl alcohol. It has been established that during the sintering of electroerosive materials made of alloy X13 by the method of spark plasma sintering, the main elements on the surface of the particles are Fe, Cr, Mn, and the particles have a generally regular spherical shape.

Features of the formation of the structure and properties of powder steels with additives that activate diffusion processes during sintering

Effect of activating the sintering process of powder steel alloyed with nickel or chromium by grinding the initial powders and introducing alkali metal compounds was investigated. The kinetics of grinding the initial iron powders, Cr30, and a mixture of iron powders with 4 % nickel was studied. It is shown that, depending on the hardness of the powder, it is grinded in three or two stages. When grinding more hard powders, there is no stage of intensive deformation of particles and an increase in their size. Crystalline lattice defects resulting from grinding of powders accelerate diffusion processes. This reduces sintering temperature by 100–200 °С compared to the sintering temperature of steels from the initial powders, contributes to a homogeneous structure, reduces porosity by 4–17 %, and increase strength of powder steels by 1.5–1.6 times. The mechanism of the effect of sodium bicarbonate on the acceleration of diffusion of carbon, nickel and chromium into iron has been established. With the introduction of sodium bicarbonate under the action of water vapor, formed upon its decomposition to carbonate, thin oxide films are formed on iron particles, which are actively recovered in a protective-recovering atmosphere during sintering. This leads to formation of a metal contact between the particles, acceleration of the self-diffusion of iron atoms and the diffusion of alloying additives into iron by 5–7 times, depending on the sintering temperature and the amount of added additive. Sodium forms nanodispersed complex compounds of the ferritic type Na3Fe5O9 along the grain boundaries of the iron base, which provide grain refinement and the formation of a homogeneous structure. Changes in the structure of powder steel with the introduction of sodium bicarbonate cause an increase in its strength by 1.5–1.7 times. The results can be used to obtain structural products from alloyed powder steels.

Modeling and testing of manufacturing technique of bimetallic billet with surface layer from powder high-speed steel

The parameters for the producing of bimetallic billets from powder steel W6Mo5 (outer layer) and steel 5CrNiMo (core), eliminating the formation of cracks at the boundary of the bimetal layers are optimized by mathematical modeling methods. Defect-free bimetallic billets are made based on the simulation results using the technology of hot isostatic pressing followed by heat treatment. The produced bimetallic billets have level of mechanical properties comparable to standard cast and deformed high-speed steels and more uniform structure at signifi cantly lower cost of products.