International Scientific Journals
of Scientific Technical Union of Mechanical Engineering "Industry 4.0"

Surface saturation with boron of Fe-C-Cu construction powder materials aims to improve the surface hardness of the articles and hence improve wear, contact strength and other mechanical properties. This study investigates the influence of single-component diffusion enrichment modes with boron of semi-permeable powder metallurgical samples from the Fe-C-Cu system. The powder samples on the basis of iron powders NC 100.24 to which 0,3 ÷ 2,5% Cu and 0,4% carbon were added were subjected to the study. Diffusion saturation with boron was carried out in semi-permeable saturation media with a composition of 84% Na2B4O7 + 12% SiC + 4% K2Cr2O7 at temperatures 850 ÷ 950 ° C for 2 ÷ 4 hours. Graphical dependencies are presented for the variation of the diffusion slit thickness in the longitudinal section of the test samples depending on their density, duration and saturation temperature. The experimental results obtained are compared with those obtained by combining pure iron samples with the same technological parameters.

The main characteristic of the powder metallurgical materials that distinguishes them from the summer ones is the presence in them of residual porosity. For this reason, the processes of their thermochemical treatment are differ significantly from those occurring at saturation of dense ones. In the present paper the impact of technological processes such as boronizing, chromizing, siliconizing, carburizing, borocarburizing, etc., is monitored on the kinetics of diffusion layer growth in powder materials with a porosity of 5÷35%. The specimens of iron powders NC 100.24 and those doped with 2% Cu were subjected to study. The samples were pressed with an effort of 200 ÷ 800MPa and sintered for 0.5h at 1150°C in dissociated NH3 medium. Thermochemical treatment was conducted at 950°C for 4 hours in semi-permeable saturation media. Graphical dependencies for varying the thickness of diffusion coatings in different thermochemical treatment modes are presented, depending on the porosity of the saturation materials.

As a result of sintering the powder workpieces large part of the separated free energy leads to higher density of sintered body. This in turn is accompanied by a change in linear dimensions of workpieces. These linear changes in addition to the alloying elements in iron matrices largely depend on the technological parameters of the sintering process – temperature, duration, protective atmosphere and others. This study monitored the impact of the type of protective atmosphere and duration of sintering on the size change of powder workpieces of iron powder ASC 100.29 alloyed 0,15 ÷ 0,60% P. Sintering is conducted at 1150ºC a duration of 15 ÷ 90min in two protective environments – endothermic gas and dissociated ammonia. Presented are graphical relationships of the relative change in the diametric dimensions of the workpieces in dependence on the concentration of phosphorus in them, the type of the protective atmosphere and the duration of sintering.

In the present study the influence of the monitored type iron powder, and the process of sintering in the presence of a liquid phase on the tensile strength of the powder metallurgical samples of the system Fe-C-Cu . Research samples are subjected made of three types of iron powders – ASC 100.29, SC 100.26 and NC 100.24. Thereto is added of 0,2 to 0,8% carbon and 2,5% copper. After sintering the measured density of the samples in the range of 6,20÷7,00g/cm³. Are presented graphics, amending the tensile strength of the samples depending on their density and the concentration of copper and carbon in the iron matrix.