In-situ quench and tempering for microstructure control and enhanced mechanical properties of laser cladded AISI 420 stainless steel powder on 300M steel substrates

Effects of Low-Temperature Tempering on Microstructure and Properties of the Laser-Cladded AISI 420 Martensitic Stainless Steel Coating

“…By calculating the formulas of Equations (1) and (2), the Cr eq and Ni eq values were 14.6 and 8.87, respectively, as indicated by the red dot in Figure 2a. It is worth mentioning that the 0.55 wt % Ni present in this work, as indicated in Table 1, is higher than those reported in AISI 420 SS with a lean Ni element [2][3][4][5][6][7]. In view of the high hardenability of AISI 420 stainless steel, together with the presence of the austenite stabilizer Ni, it can be reasonably speculated that martensite (M) and austenite (A) coexist in the as-cladded coating in this work.…”

“…By further comparing the coating zones with high magnifications, the lath-shaped martensite in the as-tempered specimen ( Figure 3d) was much finer than that in the as-cladded specimen (Figure 3b). Given that the martensitic transformation start temperature (Ms) of AISI 420 SS is about 160 • C [7], the partitioning of martensite can be expectedly initiated at the tempering temperature of 210 • C used in this work.…”

“…However, there was only a little reporting in the literature on laser-cladded AISI 420 SS coatings [3][4][5][6][7]. For instance, Krakhmalev et al [3] investigated the thermal cycling by numerical simulation and the in-situ microstructural evolution by an experiment with AISI 420 SS prepared by a selective laser melting (SLM) technique.…”

“…They found that PCHT could lead to not only reductions of micro-hardness and residual stress, but also the precipitation of tempered martensite and more carbides [6]. Recently, Sun et al [7] reported an in-situ quench and tempering treatment by introducing a laser idle time of 80 s between clad tracks, and demonstrated a significant improvement in the ductility of the AISI 420 SS coating on a 300M steel substrate. However, it is commonly believed that the tempering process using a conventional furnace is more suitable to achieve a homogeneous microstructure and properties for large-scale components [8].…”

Process-property-microstructure relationships in laser-powder bed fusion of 420 stainless steel.

“…The mechanical behavior of 420 stainless steel is highly dependent on the microstructure [113]. Low temperature isothermal tempering was implemented by heating the as-printed L-PBF 420 stainless steel parts in a furnace at 315°C for 2 hours followed by air cooling.…”