Wear Resistance of Cemented Carbide Surfacing Layers After Heat Treatment

Literature Overview

This paper, published in 2002 in the journal China Surface Engineering (Vol. 15, Issue 3, pp. 17-19) by Liu Yong, Wang Shunxing, and Tian Baohong from the Department of Materials Science and Engineering at Luoyang Institute of Technology, investigates the wear resistance and corrosion-wear performance of cemented carbide surfacing layers following heat treatment. The study compares three surface treatment approaches: boron-carbon-nitrogen (BCN) co-implantation layers, tungsten carbide-type cemented carbide (D707) surfacing layers, and high-carbon high-chromium cast iron-type cemented carbide (D618) surfacing layers. The work addresses the important question of whether post-welding heat treatment can enhance the performance of cemented carbide surfacing layers and simplify the overall surface engineering process.

Comparative Surface Treatment Methods

The three surface treatment methods evaluated in this study represent different approaches to achieving wear and corrosion resistance on steel substrates. BCN co-implantation is a surface modification technique that introduces boron, carbon, and nitrogen into the near-surface region of the substrate, creating a hardened layer with improved tribological and corrosion properties. The D707 and D618 surfacing layers are produced by welding or spraying cemented carbide materials onto the substrate surface, providing a thick, hard overlay with distinct mechanical properties.

Heat Treatment Effects on Surfacing Layer Performance

The study investigated two heat treatment conditions: 850 degrees Celsius air cooling and 850 plus or minus 5 degrees Celsius oil quenching followed by 400 degrees Celsius tempering. The results showed that both cemented carbide surfacing layers, D707 and D618, achieved high hardness and excellent corrosion-wear performance after these heat treatments. The heat treatment serves multiple purposes: it relieves welding residual stresses that can cause cracking and distortion, it modifies the microstructure of the surfacing layer to optimize the balance between hardness and toughness, and it can promote the formation of additional hard phases through diffusion and precipitation reactions.

The 850 degrees Celsius air cooling treatment is relatively simple and can be performed in a standard furnace, making it accessible for industrial applications. The oil quench and temper treatment provides more precise microstructural control but requires additional equipment and process steps. The fact that both treatments yield good results suggests that the cemented carbide surfacing layers have a degree of microstructural stability that is not easily degraded by moderate thermal exposure.

Corrosion-Wear Performance Analysis

Corrosion-wear is a synergistic degradation mechanism where chemical attack and mechanical wear interact to accelerate material loss beyond what either mechanism would cause independently. The cemented carbide surfacing layers, with their high carbon and chromium content, form protective oxide films that resist chemical attack. The hard carbide phases (WC in D707 and Cr7C3 in D618) provide mechanical resistance to abrasive and adhesive wear. The combination of these features results in superior corrosion-wear performance compared to untreated steel substrates.

The BCN co-implantation layer, while thinner than the cemented carbide surfacing layers, also demonstrated good corrosion-wear resistance. However, the cemented carbide surfacing layers offered the advantage of greater thickness, which provides longer service life before substrate exposure, and the potential for easier repair through re-surfacing.

Engineering Practice and Process Simplification

A significant practical finding of this study is that the heat treatment of cemented carbide surfacing layers simplifies the overall surface engineering process. In many industrial applications, multiple surface treatment steps are required to achieve the desired combination of hardness, wear resistance, and corrosion resistance. By demonstrating that a single cemented carbide surfacing followed by heat treatment can achieve comparable or superior performance to multi-step processes, this work offers a path to process simplification and cost reduction.

For maintenance and repair operations in industries such as mining, cement, and power generation, where components are frequently subjected to combined wear and corrosion, the D707 and D618 surfacing layers with appropriate heat treatment represent a practical and effective solution. The heat treatment step also serves to relieve welding stresses, reducing the risk of delayed cracking and improving the long-term reliability of the surfacing.

Study Insights and Reflections

This work highlights the importance of post-welding heat treatment in optimizing the performance of cemented carbide surfacing layers. The relatively straightforward heat treatment conditions of 850 degrees Celsius provide a practical processing window that can be implemented in most industrial welding shops. The comparison with BCN co-implantation provides useful context for selecting between thin surface modification and thick surfacing approaches based on the specific requirements of the application. The emphasis on corrosion-wear performance, rather than pure wear resistance, reflects the real-world service conditions encountered in many industrial environments and underscores the value of integrated surface engineering solutions.