The structure, phase composition, and residual stresses of diffusion boride layers formed by thermal-chemical treatment on the die steel surface

OBRABOTKAMETALLOV MATERIAL SCIENCE Vol. 23 No. 2 2021 Ta b l e 3 Concentration of elements in the surface layer of the sample after TCT at a temperature of 950 ° C, wt. % * Spectrum No B C V Cr Fe W Total Spectrum 1 6 4.9 0.3 8.3 77.8 2.7 100.00 Spectrum 2 – 5.4 0.7 9.3 72.1 12.5 100.00 Line spectrum (1) 6.2 4.3 – 8.8 79.2 1.5 100.00 Line spectrum (2) 1.9 6.1 – 9.8 68.8 13.4 100.00 Line spectrum (3) 3.1 6 – 7.9 80 3 100.00 Line spectrum (4) – 8 – 11.2 78 2.8 100.00 Line spectrum (5) – 8.6 – 10.8 72.1 8.5 100.00 * Quantitative analysis is given to reflect the concentration variation depending on the distance from the surface. The actual values are not possible to define by EDS analysis. Ta b l e 4 Concentration of elements in the surface layer of the sample after TCT at a temperature of 1050 °C , wt. % * Spectrum No B C O Si V Cr Fe W Total Spectrum 1 10.5 4.5 2.5 – – 4.1 65.4 13 100.00 Spectrum 2 10.8 5.1 – – – 11.3 69 3.8 100.00 Spectrum 3 3.1 4 2.2 0.5 – 6.6 80.8 2.8 100.00 Line spectrum (1) 11.8 3.8 – – – 10.7 71.5 2.2 100.00 Line spectrum (2) 1.7 4.8 – – 0.5 11.3 71.8 9.9 100.00 Line spectrum (3) 3.3 5.5 – – 10.4 74.2 6.6 100.00 Line spectrum (4) – 7.3 – – – 13.5 77.4 1.8 100.00 Line spectrum (5) – 7.4 – – – 10.5 76.7 5.4 100.00 Spectrum 9 – 3.7 – – – 12.8 77.7 5.8 100.00 * Quantitative analysis is given to reflect the concentration variation depending on the distance from the surface. The actual values are not possible to define by EDS analysis. problem is being solved by the monoboride layer formation consisting of Fe 2 B boride with a developed transition zone. The experiments discovered a single-phase Fe 2 B layer formation after boriding at 950 °C. Although XRD revealed the only FeB phase for high-temperature TCT, the boride layer had a two- phase composition, and Fe 2 B presence was confirmed by numerous reference data and partially including experimental findings, for example, microhardness values [1–4, 19–22]. Thus, two temperature modes of boriding with the same exposure led to the formation of layers with the required phase composition for further RS investigation. The microhardness distribution pattern correlated well with the RS distribution, for example, high gra- dients were observed in the diffusion layer and in the adjacent (transition) zone after low-temperature treatment. On the contrary, after boriding at 1050 °С the RS and microhardness distributions over the layer thickness were smoother, except for the transition zone at 105–160 µm distance from the surface, where