## 4 Results and Discussion
The ASMC composition lacks carbon, but it contains components that decompose, activate the surface, reduce surface energy and thus produce active hydrogen under the influence of high temperatures and pressures. During the TDT of Steel C22 when using mineral oil as the process liquid, the white, strengthened layer forms a relatively thin layer, with a maximum thickness of 40-50 \(\upmu\)m. When applying ASMC, the maximum white layer thickness increases sharply to 80-90 \(\upmu\)m. The strengthened layer of the greatest thickness and microhardness is obtained when mineral oil with AAP is used as the process liquid. It is even throughout its length, with a thickness of 100-110 \(\upmu\)m (Figure 4). Similar research results were obtained during the TDT of Steel C45 after QH and LTT and Steel 41 Cr4 after QH and LTT. Thus, the thickness of the strengthened white layer obtained after the TDT of Steel C45 using mineral oil is 110-120 \(\upmu\)m, and if ASMC is used, it increases to 180-200 \(\upmu\)m. The largest thickness (230-240 \(\upmu\)m) is obtained during treatment using mineral oil with AAP as the process liquid (Figure 5). When Steel 41 Cr4 is strengthened with mineral oil, the white layer thickness is 160-180 \(\upmu\)m, with ASMC applied it reaches 200-220 \(\upmu\)m, and if mineral oil with AAP is used, the value is 260-280 \(\upmu\)m (Figure 6). Figure 3: Microhardness of Armco-iron using different process liquids: O—mineral oil; _AAP_—mineral oil with active additives containing polymers; _W_—water; _ASMC_—aqueous solution of mineral salts based on magnesium and calcium chlorides. Studies have shown that after the TDT of samples of Steel C45 using mineral oil with AAP as the process liquid, grain (crystallites) size \(D\) on the treated surface is between 12-14 nm [54]. The grain size increases with increasing depths of the strengthened layer, and at a depth of 150 \(\upmu\)m, the grain size increases to 23-25 nm. At a depth of 250 \(\upmu\)m, which is close to the thickness of the strengthened layer, the grain size becomes 60-65 nm. Beyond this, the grain size increases to the initial value (3-5 \(\upmu\)m). The microhardness of Steel C22 and Steel C45 is substantially influenced by the use of ASMC and mineral oil with AAP as the process liquid during the TDT. Thus, the microhardness of the white layer obtained for Steel C22 using ASMC is 4.4-4.6 GPa, using mineral oil with AAP, it is 5.0 GPa, and using mineral oil, it is 3.8 GPa and 2.5 GPa of the main structure. The greatest value of microhardness is for Steel C45. Figure 4: Microhardness of Steel C22 using different process liquids: \(O\)—mineral oil; \(AAP\)—mineral oil with active additives containing polymers; \(ASMC\)—aqueous solution of mineral salts based on magnesium and calcium chlorides. Figure 5: Microhardness of Steel C45 (QH, LTT) using different process liquids: \(O\)—mineral oil; \(AAP\)—mineral oil with active additives containing polymers; \(ASMC\)—aqueous solution of mineral salts based on magnesium and calcium chlorides. After the TDT of Steel 41 Cr4 using mineral oil with AAP, the microhardness of the strengthened layer is the largest and equals 9.1 GPa, and if ASMC is used, the microhardness of the white layer is also higher compared to using mineral oil and equals 8.6 GPa and 7.6 GPa, respectively, with the basic structure microhardness equal to 5.0 GPa. There is an area with reduced hardness and increased etchability beneath the strengthened layer during the TDT of samples made of pre-quench-hardened steel and the LTT. The application of ASMC and mineral oil with AAP over the course of TDT increases the thickness of the white layer, as well as its microhardness, and the area of tempering with reduced hardness also increases. In this area, the heat flow is insufficient to form a strengthened layer but is sufficient for the high-temperature tempering of the pre-quench hardened metal sample (the samples had QH and LTT before TDT).