Key Takeaways & Executive Findings
- •• • NM500 steel exhibits a fine lath martensitic microstructure with a grain size of 7.08 μm, yielding high hardness and a low-temperature wear rate of 1.29×10−6 mm3/(N·m) at −50 to 0 °C; this indicates that the alloy is optimally suited for cryogenic abrasive environments, such as cold-climate mining or LNG handling equipment, where material loss is minimized. • • At 100, 200, 300, and 600 °C, wear rates escalate to 18×10−6, 22.7×10−6, 46.7×10−6, and 128×10−6 mm3/(N·m), respectively, representing a 14- to 99-fold increase over the cryogenic regime; this sharp degradation underscores that continuous high-temperature service above 300 °C is economically unviable without surface engineering or alloy modification. • • The friction coefficient drops to a minimum of 0.3 at elevated temperatures, a 50% reduction compared to low-temperature values, due to the formation of continuous oxide films; however, at 600 °C, oxide film delamination and reduced texture strength cause a transition to oxidative wear as the dominant mechanism, accelerating material loss and necessitating protective coatings or alloying additions for high-temperature applications. • • The wear mechanism shifts from abrasive wear at −50 to 0 °C, to mixed abrasive-fatigue-oxidative wear at 100–200 °C, and finally to oxidative wear with minor abrasive wear at 300–600 °C; this temperature-dependent transition provides a predictive framework for selecting NM500 in industrial tribosystems, where operating temperature must be matched to the dominant wear mode to avoid premature failure.
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Abstract
The tribological behavior of NM500 wear-resistant steel was systematically evaluated across a wide temperature range from −50 to 600 °C to elucidate the influence of temperature on wear resistance and to provide a theoretical basis for service life extension. Friction and wear tests were conducted using a high-temperature tribometer under a normal load of 150 N, rotational speed of 354 r/min, wear track diameter of 15 mm, and test duration of 60 minutes. The microstructure was characterized by SEM and EBSD, while worn surfaces were analyzed using XRD, SEM, and 3D laser confocal microscopy. NM500 steel exhibits a fine lath martensitic structure with a grain size of 7.08 μm, conferring high hardness and superior wear resistance. At cryogenic temperatures (−50, −25, 0 °C), the wear mechanism is predominantly abrasive wear, with a wear rate of only 1.29×10−6 mm3/(N·m). As temperature increases, oxide formation on the worn surface intensifies, friction coefficient decreases to a minimum of 0.3 (50% lower than at low temperature), and wear rate increases significantly: 18×10−6, 22.7×10−6, 46.7×10−6, and 128×10−6 mm3/(N·m) at 100, 200, 300, and 600 °C, respectively. The dominant wear mechanism transitions from abrasive wear at low temperatures to oxidative wear with adhesive wear at elevated temperatures. At 600 °C, thermal softening, reduced texture strength, and oxide film delamination exacerbate material loss, shifting the mechanism to oxidative wear as the primary mode with adhesive wear as secondary.
1. Introduction
Commercial wear-resistant steels such as NM500 are widely deployed in mining, construction, and material handling equipment, where abrasive and impact wear dominate. However, existing grades are typically optimized for ambient or low-temperature service, and their performance under wide temperature fluctuations—ranging from cryogenic conditions in cold climates to elevated temperatures in hot processing or high-friction environments—remains poorly characterized. This knowledge gap leads to unpredictable service life, frequent unplanned maintenance, and excessive replacement costs. The lack of systematic tribological data across a broad temperature spectrum prevents engineers from reliably predicting wear rates and selecting appropriate materials for variable thermal conditions.
This study addresses the bottleneck by conducting controlled friction and wear tests on NM500 steel from −50 to 600 °C under a constant load of 150 N and rotational speed of 354 r/min. By correlating microstructural features (lath martensite, grain size 7.08 μm) with wear track morphology, oxide phase evolution, and wear rates, the work establishes a temperature-dependent wear mechanism map. The findings provide a quantitative basis for extending NM500 service life through informed thermal management and surface protection strategies, and they offer a validated dataset for finite element wear simulations in industrial tribosystems.
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MA Heng, LI Zhenwei, WANG Zhongxue, LI Wenquan, ZHANG Qingpu, HAN Wenzheng, HE Kang, CUI Hongzhi (2026). Research on Wear Resistance and Wear Mechanism of NM500 Steel in a Wide Temperature Range. Surface Technology (表面技术). https://doi.org/10.16490/j.cnki.issn.1001-3660.2026.11.005
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Frequently Asked Questions
What is the dominant wear mechanism at cryogenic temperatures, and how does it affect industrial performance?
At −50, −25, and 0 °C, the dominant mechanism is abrasive wear, with a wear rate of only 1.29×10−6 mm3/(N·m). The fine lath martensitic structure (grain size 7.08 μm) and complex dislocation/texture networks reduce local stress concentration and delay crack initiation, enhancing resistance to ploughing. Industrially, this means NM500 is highly suitable for cold-climate applications such as Arctic mining or LNG transport, where low material loss translates to extended service intervals.
Why does the wear rate increase dramatically at 600 °C, and what are the implications for high-temperature service?
At 600 °C, the wear rate reaches 128×10−6 mm3/(N·m), a 99-fold increase over cryogenic conditions. This is attributed to thermal softening, reduced texture strength, and delamination of the continuous oxide film. The wear mechanism shifts to oxidative wear with adhesive wear as a secondary mode. For industrial applications, operating NM500 continuously above 300 °C is impractical without protective coatings or alloy modifications, as the material loss rate becomes economically prohibitive.
How does the friction coefficient vary with temperature, and what does it indicate about oxide film formation?
The friction coefficient decreases with increasing temperature, reaching a minimum of 0.3 at elevated temperatures—a 50% reduction compared to low-temperature values. This is due to the formation of continuous oxide films that act as solid lubricants. However, at 600 °C, oxide film delamination occurs, which temporarily reduces friction but accelerates wear. The data suggest that while oxide films can reduce friction, their stability is critical; at temperatures above 300 °C, film breakdown leads to increased wear rates.
What is the role of microstructure in the wear performance of NM500 steel?
The fine lath martensitic structure with a grain size of 7.08 μm provides high hardness and uniform deformation behavior. At low temperatures, the complex dislocation and texture networks reduce local stress concentration and delay crack initiation, enhancing abrasive wear resistance. At high temperatures, the same microstructure undergoes softening and texture weakening, which promotes plastic deformation and oxidative wear. Thus, microstructural stability is a key factor in determining the temperature-dependent wear transition.
What are the practical implications of the wear mechanism transition for material selection in industrial tribosystems?
The transition from abrasive wear (below 0 °C) to mixed abrasive-fatigue-oxidative wear (100–200 °C) and finally to oxidative wear (300–600 °C) provides a predictive framework. For applications with operating temperatures below 100 °C, NM500 offers excellent wear resistance. For higher temperatures, surface engineering (e.g., coatings) or alloying additions are necessary to maintain oxide film integrity and reduce wear rates. This temperature-dependent map enables engineers to match material selection to specific thermal conditions, optimizing cost and service life.
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