Mechanical properties of sinter hardened sintered steels prepared by hybrid alloying

Microstructural Investigation and Impact Strength of Sinter-Hardened PM Steels: Influence of Ni Content and Tempering Temperature

“…These properties of Ni-rich austenite areas could justify the highest impact energy values being measured for the 4Ni samples in comparison with the 0Ni samples, for all tempering conditions. Hence, Ni addition has been proven to enhance impact strength, as previously observed by [47].…”

“…Such an experimental finding was supported by LOM observation of the fracture profile (Figure 11a), which showed how the fracture path did not preferentially lie on Ni-rich areas (residual austenite). In addition, the SEI-SEM fracture profile analyses pointed out how austenite areas could play a role in stopping fracture propagation because of their extensive plastic deformation capability (Figure 11b) [29,38,47]. Previous studies in the literature have exposed how crack paths can be influenced by pore geometry, distance between the pores, and local stress directions, as well as their interactions with matrix microstructures surrounding the pores [48][49][50].…”

“…The 0Ni samples showed the highest macrohardness and martensite microhardness values for all conditions compared to the 4Ni samples. Such a result was due to the different compositions, especially Ni and C contents (see Table 1): by increasing C content, hardness increased [19] and, at the same time, the Ni content promoted the formation of soft Ni-rich (retained austenite) areas [47]. In addition, Ni-rich austenite areas were involved in a transformation during tempering, forming a bainite-like structure rich in carbides [45,48], according to the measured microhardness values (Table 2).…”