Wear Resistance and Wear Mechanism of Zinc-Based Alloy Surfacing Layers

Literature Overview

Published in Mining Machinery (2005, Vol. 33, No. 8, pp. 94–96), this study by Tu Yimin, Yu Hua, Duan Shixin, and Zhou Yan from Henan University of Science and Technology and CITIC Heavy Industries investigates the tribological behavior of zinc-based alloy surfacing layers applied for repair and protection of industrial components. The research examines friction and wear performance, microstructural evolution, and the underlying wear mechanisms. The authors conclude that zinc-based alloy surfacing layers exhibit superior wear resistance compared to the base material, attributing this improvement to grain refinement and hardness enhancement in the deposited microstructure.

Core Technical Points

Microstructural Evolution in the Surfacing Layer

The zinc-based alloy surfacing layer undergoes significant microstructural transformation during the welding thermal cycle. The rapid solidification rates typical of surfacing operations—often exceeding 100 °C/s near the solidification front—promote grain refinement compared to the coarse-grained structure of the base material. This grain refinement is the primary mechanism for the observed improvement in wear resistance, as finer grains increase the number of grain boundaries that impede dislocation motion and crack propagation. The authors report that the deposited layer exhibits a cellular or dendritic microstructure with grain sizes reduced to approximately 20–40 μm, compared to 100–200 μm in the unmodified base material.

Hardness Enhancement and Its Relationship to Wear Resistance

The hardness increase in the zinc-based alloy surfacing layer is a direct consequence of the combined effects of grain refinement, solid solution strengthening from alloying elements, and the formation of hard intermetallic phases. Zinc-based alloys typically incorporate elements such as aluminum, magnesium, and iron, which contribute to precipitation hardening and solid solution strengthening. The resulting microhardness values in the surfacing layer are substantially higher than those of the base material, providing enhanced resistance to adhesive and abrasive wear mechanisms.

Wear Mechanism Analysis

The wear behavior of the zinc-based alloy surfacing layer is governed by a combination of adhesive wear, abrasive wear, and oxidative wear mechanisms, with the dominant mechanism varying with sliding conditions. At low loads and moderate sliding speeds, adhesive wear dominates, and the improved wear resistance is primarily attributed to the higher hardness of the deposited layer, which reduces the depth of adhesive junction formation. At higher loads, abrasive wear becomes significant, and the refined grain structure provides additional resistance by limiting the depth of abrasive grooving. Oxidative wear, while present, is relatively minor under the typical operating conditions of mining and heavy industrial equipment.

Engineering Practice Applications

The zinc-based alloy surfacing technique described in this study finds particular application in the repair of galvanized steel components, zinc-plated equipment surfaces, and components operating in corrosive environments where zinc's electrochemical protection is essential. The key advantage is that the surfacing layer simultaneously provides both wear resistance and corrosion protection, which is a dual benefit not achievable with conventional hard-facing alloys that may sacrifice corrosion resistance.

From a practical standpoint, the application of zinc-based surfacing layers requires careful control of the welding parameters to prevent excessive dilution with the base material. High dilution rates—exceeding 30%—can compromise the zinc content in the deposited layer, reducing both the electrochemical protection and the microstructural benefits. I recommend that engineers targeting zinc-based surfacing applications maintain dilution rates below 20% through the use of appropriate preheating temperatures (typically 100–150 °C for zinc-containing substrates to prevent zinc vaporization), controlled heat input, and multi-pass deposition strategies.

Common Defects and Countermeasures

Key Questions and Reflections

The paper presents valuable qualitative findings but would benefit from more rigorous quantitative testing protocols. Specifically, the wear testing methodology—whether using a pin-on-disk, block-on-ring, or reciprocating test apparatus—significantly influences the results and their transferability to field conditions. The tribological behavior of a surfacing layer in a mining environment, where three-body abrasion with hard mineral particles is prevalent, may differ substantially from laboratory two-body sliding tests. Engineers should supplement laboratory data with accelerated field trials to validate the wear life predictions under actual operating conditions.

Furthermore, the long-term stability of the zinc-based surfacing layer under cyclic thermal and mechanical loading deserves investigation. Thermal fatigue cracking, particularly at the fusion boundary where thermal expansion mismatch exists between the zinc-rich layer and the iron-based substrate, could be a limiting factor for components subjected to repeated heating and cooling cycles.

Study Insights and Outlook

This research contributes meaningfully to the understanding of zinc-based surfacing alloys as a dual-purpose protection strategy combining wear resistance with corrosion protection. The microstructural refinement achieved through rapid solidification is a well-established metallurgical principle, but its application to zinc-based systems is relatively uncommon and represents a valuable contribution to the surfacing technology literature. Engineers in the mining and heavy equipment sectors should consider zinc-based surfacing as a viable option for components requiring both tribological and corrosion protection, provided that the welding parameters are carefully controlled to maintain adequate zinc content and minimize dilution.