Role of preplaced silicon on a TIG processed SiC incorporated microalloyed steel

Abstract

Research aimed at enhancing the surface properties of carbon steels by incorporating fine silicon carbide particulates has had limited success because the dissolution of the ceramic occurred. This research considers a method of reducing SiC dissolution by generating a high Fe–Si liquid which protects the ceramic. Three particulate groups were investigated, (1) ∼ 5 µm SiC, (2) ∼45 µm Si +∼ 5 µm SiC, and (3) ∼45 µm Si, all incorporated into a microalloyed steel using a tungsten inert gas process. Detailed microhardness of the melt zones together with microstructural analysis showed that the addition of Si resulted in a cracked hard layer containing SiC. However, in Specimen 1, a thicker, hardcrack-free layer resulted from the microstructure developed by the dissolution of SiC.

Advances in Surface Engineering Using TIG Processing to Incorporate Ceramic Particulates into Low Alloy and Microalloyed Steels – A Review

“…Figure 1 shows schematic drawings which give the track section dimensions and positions of thermocouples (a) of the BM LA steel used for TIG processing incorporating TiC particulates, (b) of the BM MA steel incorporating ~5 µm or ~75 µm SiC particulates [26,33,34].…”

“…Figure 4 also shows that a much coarser macrostructure is developed under He and N shielding gases, and that the surface roughness in these [26] by considering the effect on microhardness and microstructure through the incorporation of SiC particulates in an MA steel plate by TIG processing using energy inputs of 420 Jmm -1 or 840 Jmm -1 , with Ar as a shielding gas [30,33,34]. The dimensions and thermocouple positions in the MA steel plate was as shown in Figure 1(b).…”

“…Research on the Fe-Si-C system by Kawanishi et al [39] suggests that a high Si content could decrease SiC dissolution in liquid iron. This was developed further by Baker et al [34] ,who placed layer of silicon particulates next to an MA steel specimen, with the intention of forming a high Fe-Si-C liquid phase, before a second layer comprised of ∼5 µm SiC particulates was incorporated into the melt. An energy input of 420 Jmm −1 was used, selected as the optimum in a previous project [33] for achieving a high hardness to a depth >1 mm without porosity or cracking.…”

“…In the work by the present authors presented in nine papers [26][27][28][29][30][31][32][33][34], the TIG processing conditions used similar to those shown to be suitable by others [35,36]. The system first chosen to explore these features was that of a low alloy steel, initially TIG processed to incorporate TiC particulates [26,27].…”

“…The ~5 µm SiC was expected to fully dissolve, nucleating new phases during cooling. On the other hand, the ~75 µm SiC would be expected to show only partial dissolution, and the microstructure also benefiting from nucleation of new phases [28][29][30][31][32][33][34] A feature of much of this work was the examination of variations in temperature along the TIG melted track, plus in some experiments, along different tracks which were overlapped to treat an area of the parent plate [27,28].…”