Wear Resistance of Industrial Pure Iron Treated by Nitriding and Quenching Followed by Aging Process

Abstract

The wear resistance of iron nitrides compound layers and a high nitrogen martensite phase formed in the material surface for industrial pure iron, treated by nitriding and quenching followed by aging process were studied experimentally. Both the compound layer without pores by lowering the nitriding temperature and the high nitrogen martensite phase, showed the same tendency to high wear resistance. On the other hand, the pores in the compound layer made by the longer nitriding time decreased the wear resistance due to the acceleration of crack propagation. Metal ows were observed at the ε-phase in the compound layer very close to the surface after a sliding test. However, no strain hardening was observed. It was also found that the metal ows on a large part of the martensite layer and the hardness increased considerably.These results revealed that the high hardness ε-phase shows high wear resistance due to the plastic deformation, whereas the nitrogen martensite shows high wear resistance by the plastic deformation accompanied with the strain hardening.

Effect of Nitriding-Quenching and Carburizing-Quenching Processes on the Wear Resistance of the Sintered Pure Iron

“…To examine the wear characteristics, the sliding test was conducted using the "ring-on-plate" sliding test machine. This test was performed as described previously 16) and its schematic illustration was shown in obtained from the wear profiles 16) . The specific wear rate (W s ) was obtained from the wear volume (V), the test load (W) and the sliding distance (L) according to as follows:…”

“…Many surface hardening processes of the wrought steel, such as carburizing-quenching (CQ) and carbo-nitriding-quenching (CNQ) have been developed to improve the wear resistance [10][11][12][13] . However, since these processes comprised of the carburizing conducted at the high temperatures [14][15][16] , the dimensional changes often take place during the treatments. To override this serious problem, nitridingquenching (NQ) treatment has recently been developed [15][16][17][18] .…”

“…However, since these processes comprised of the carburizing conducted at the high temperatures [14][15][16] , the dimensional changes often take place during the treatments. To override this serious problem, nitridingquenching (NQ) treatment has recently been developed [15][16][17][18] .…”

“…During the heating process, nitrogen atoms diff use onto the steel surface, which is subsequently quenched to form the iron-nitrogen martensite phase. The hardened surface layer includes the ironnitrogen martensite and the iron nitride compounds such as ε-Fe 2~3 N and γ'-Fe 4 N phases [15][16][17][18][19] . Especially, the quenching from the austenitizing temperature in the single-phase austenite region produced the nitrogen martensite without any iron nitride [16][17] .…”

“…We have previously described the effects of NQ conditions on the wear properties of the hot-rolled industrial pure iron 16) .…”