Wear Behavior and Mechanism of a Cr-Mo-V Cast Hot-Working Die Steel

Abstract

The wear behavior and mechanisms of a Cr-Mo-V cast hot-working die steel with three microstructures (tempered martensite, troostite, and sorbite) were studied systematically through the dry-sliding wear tests within a normal load range of 50 to 300 N and an ambient temperature range of 298 K to 673 K (25°C to 400°C) by a pin-on-disk high-temperature wear machine. Five different mechanisms were observed in the experiments, namely adhesive, abrasive, mild oxidative, oxidative, and extrusive wear; one or more of those mechanisms would be dominant within particular ranges of load and temperature. The transition of wear mechanisms depended on the formation of tribo-oxides, which was related closely to load and temperature, and their delamination, which was mainly influenced by the matrix. By increasing the load and ambient temperature, the protective effect of tribo-oxides first strengthened, then decreased, and in some cases disappeared. Under a load ranging 50 to 300 N at 298 K (25°C) and a load of 50 N at 473 K (200°C), adhesive wear was the dominant wear mechanism, and abrasive wear appeared simultaneously. The wear was of mild oxidative type under a load ranging 100 to 300 N at 473 K (200°C) and a load ranging 50 to 150 N at 673 K (400°C) for tempered martensite and tempered troostite as well as under a load of 100 N at 473 K (200°C) and a load ranging 50 to 100 N at 673 K (400°C) for tempered sorbite. At the load of 200 N or greater, or the temperatures above 673 K (400°C), oxidative wear (beyond mild oxidative wear) prevailed. When the highest load of 300 N at 673 K (400°C) was applied, extrusive wear started to dominate for the tempered sorbite.

Effect of sliding speed and hardness on wear behavior and mechanism of AISI H13 steel

“…However, another kind of oxidation wear usually presented higher wear rates, and this oxidation wear could be defined as oxidative mild-to-severe wear transition region, which indeed occurred during sliding at room temperature. This finding is different from So and coworkers’ 7–9 research but is in good agreement with Wang and coworkers’ 10–12 work. Wang et al.…”

“…Clearly, all these abovementioned characteristics from 1.5 m/s to 4 m/s are typical characteristics of oxidation wear. 11,12,18,19

Figure 3.SEM morphology of worn surfaces for 37 HRC H13 steel under sliding conditions: (a) 50 N and 0.5 m/s, (b) 50 N and 1.5 m/s, (c) 50 N and 2.68 m/s, (d) 50 N and 4 m/s, (e) 100 N and 0.5 m/s, (f) 100 N and 1.5 m/s, (g) 100 N and 2.68 m/s, and (h) 100 N and 4 m/s. EDS: Energy Dispersive X-Ray Spectroscopy.

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“…In their theories, the friction-oxide layers prevent from adhesion, thus reducing the wear rate, which was confirmed by subsequent researches. [6][7][8][9][10][11][12] In oxidation mild wear, the friction-oxide layer was considered to be a key factor in deciding wear rate. [3][4][5] Li et al's 13,14 research on the wear resistance of H13 at high temperature confirmed this view.…”

“…Recently, it was found that oxidation mild wear could not be maintained as the load reaches a certain value at elevated temperature in Wang and coworkers' researches. [10][11][12] They proposed an oxidation mild-to-severe wear transition region, where friction oxides and matrix synergistically affected the wear behavior and mechanism in the transition region. [10][11][12] Clearly, as sliding conditions becomes harsh, the protecting ability of friction oxides is gradually reduced.…”

“…[10][11][12] For roomtemperature dry sliding, So and coworkers [7][8][9] also reported that when the normal load or sliding speed reached certain value, the wear rate of the steels suddenly rose and the oxidation mild wear turned into extrusion wear. However, in So's research, the wear transition region that was proposed by Wang and coworkers [10][11][12] was not mentioned. Hence, there are still many unsolved issues related to the wear behavior and mechanism during sliding at room temperature.…”