Effect of hydrogen embrittlement and non-metallic inclusions on tensile fracture properties of 55CrSi spring steel

Abstract

The tensile fracture behavior of 55CrSi spring steels were investigated. The results demonstrate that interior inclusion and hydrogen level has a significant effect on ductility and a minimal effect on tensile strength of the spring steel. It was due to the effect of cracking from MgO-Al 2 O 3 spinel inclusion or the inclusions with a mixture of CaO, SiO 2 and part of Al 2 O 3 due to hydrogen. The results of SEM showed that the ductility reduction is connected with the formation of 'fisheye' which formed under the influence of mobile hydrogen. For the specimen containing MgO-Al 2 O 3 spinel inclusion, the fracture surface in the 'fisheye' area is mainly composed of three regions including typical quasi-cleavage mixed intergranular fracture, dimple mixed transgranular fractures and ductile fracture from the interior to the edge, whereas there is no obvious transition zone from brittle fracture to dimple fracture in the 'fisheye' area of the specimen containing inclusions with a mixture of CaO, SiO 2 and part of Al 2 O 3 .

The fatigue crack growth behavior of hydrogenated 9Cr‐1Mo steel: An experimental and numerical study

“…Several other researchers have also reported similar types of features. 56,61,[63][64][65] It can be seen that the fish eye near the surface (Figure 5A) is comparatively more prominent than those found towards the center of the fracture surface, as shown in Figure 5D. Singh et al 61 observed a similar finding and reported that the variation in the size of fish eyes is attributed to a difference in hydrogen concentration at the respective location, which is consistent with the observation of the present study.…”

“…As and when this pressure exceeds interatomic force under critical hydrogen concentration, crack initiates from these sites at a lower load than the uncharged specimen, showing reduced tensile strength. 56 Singh et al 61 and Li et al 64 reported that deep traps like inclusion cause degradation in the mechanical property of the material in the presence of hydrogen. The study by Fujita and Murakami 66 mentioned that debonding at the interface of inclusion and matrix causes void formation where the concentrated hydrogen causes cracking of GB at the edges of voids.…”

Effect of Slag Adjustment on Inclusions and Mechanical Properties of Si-Killed 55SiCr Spring Steel

“…Non-metallic inclusions have significant effects on many mechanical properties of suspension spring steel, including the strength, plasticity, toughness and fatigue properties. Li et al [23] studied the effect of inclusions on the tensile fracture properties of 55CrSi spring steel. The results demonstrated that interior inclusions have a significant effect on the ductility and a minimal effect on the tensile strength of spring steel.…”