Experimental Study on Overlay Welding Process of Tubular Cast Tungsten Carbide

Literature Overview

This paper by He Kailin, Wang Chen, and Shi Xiaohua from Jiangsu Fengshang Intelligent Technology Co., Ltd., published in Heat Treatment (Volume 40, Issue 5, 2025, pp. 23-28), addresses a practical and often overlooked engineering challenge: the overlay welding of tubular cast tungsten carbide components. The work is significant because cast tungsten carbide inserts are widely used in mining, petroleum, and material handling industries, yet their repair and extension through overlay welding have historically been problematic due to the extreme hardness, thermal shock sensitivity, and chemical inertness of the carbide phase. The authors employed two different base materials, applied overlay welding followed by various heat treatment cycles, and then characterized the overlay through Vickers hardness testing, optical microscopy, scanning electron microscopy, and wear performance evaluation.

Core Technical Findings

The study yields several findings that are directly relevant to field repair and manufacturing decisions. First, the thickness of the overlay layer and the thickness of the molten pool are critical process parameters that govern the distribution of cast tungsten carbide particles. An overlay layer that is too thin fails to properly embed and protect the carbide particles, while an excessively thick molten pool causes excessive dilution of the carbide phase and promotes the precipitation of complex carbides that degrade the wear resistance of the matrix. Second, the authors confirmed that the overlay layer achieves metallurgical bonding with the base material, which means post-overlay heat treatment is feasible without risk of interface separation. Third, medium-frequency induction quenching, particularly carburizing quenching, was found to increase the matrix hardness of the overlay layer and further enhance its wear resistance.

Process Parameter Analysis

The dilution effect is a central concern in tungsten carbide overlay welding. When the molten pool is too deep or too wide, the tungsten carbide particles dissolve into the melt and reprecipitate as smaller, less effective carbide phases. The authors observed that different dilution levels result in different matrix hardness values, which directly impacts the abrasion resistance. This finding aligns with established welding metallurgy principles regarding dilution control in hardfacing applications. The recommended practice is to use pulsed arc or short-arc welding processes that provide shallow penetration and controlled heat input.

The heat treatment approach is particularly noteworthy. Medium-frequency induction heating provides localized, rapid heating that minimizes thermal distortion of tubular geometries. Carburizing quenching introduces additional carbon into the overlay matrix, promoting the formation of fine cementite and other iron carbides that complement the retained tungsten carbide particles. This is a practical insight for maintenance engineers who need to restore service life to worn tubular components without complete replacement.

Engineering Practice Implications

From a manufacturing standpoint, this research has direct relevance to the repair of drill collars, crusher rolls, and wear parts that incorporate cast tungsten carbide inserts. The finding that metallurgical bonding is achievable opens the door to extending the service life of these components through overlay welding followed by proper heat treatment. However, the study also highlights a critical limitation: process window control is essential. The balance between overlay thickness and molten pool depth must be carefully managed to avoid carbide dilution.

In practical application, the following process guidelines can be derived from this work:

The carburizing quench recommendation is particularly valuable for field operations because medium-frequency induction equipment is portable and does not require large furnaces. This makes the approach suitable for on-site repair of large tubular components that cannot be transported to a fabrication shop.

Key Questions and Reflections

One question that arises from this study is the long-term durability of the overlay after carburizing quench treatment under cyclic loading conditions. While the study demonstrates improved hardness and wear resistance, fatigue performance under repeated impact loading, as encountered in mining and crushing applications, remains to be fully characterized. Additionally, the study does not address the effect of multiple overlay passes on carbide distribution uniformity, which is a practical concern when building up significant overlay thickness.

Another reflection concerns the economic aspect. Cast tungsten carbide is an expensive material, and the overlay welding approach offers a cost-effective repair strategy compared to complete part replacement. However, the need for precise process control and post-weld heat treatment adds complexity to the repair procedure. Maintenance teams must be trained in the specific parameter windows to achieve reliable results.

Summary

This study provides valuable experimental data on the overlay welding of tubular cast tungsten carbide components, confirming that metallurgical bonding is achievable and that medium-frequency carburizing quench treatment can significantly enhance the wear resistance of the overlay matrix. The key process insight is that both overlay thickness and molten pool depth must be carefully controlled to prevent excessive carbide dilution. For engineers working in maintenance and repair of wear-critical tubular components, this research offers a practical pathway to extend service life through controlled overlay welding combined with appropriate post-weld heat treatment.