FLS Surface Wear-Resistant Cladding Technology for Cement Engineering Applications

Literature Overview

This study note examines the application of surface wear-resistant cladding technology developed by FLS (formerly F.L.Smidth, a leading cement equipment manufacturer) for cement engineering components. Published in 2003 by Wang Fang and associated with Hainan Cement Co., Ltd., this work addresses the critical challenge of abrasive wear in cement production environments where equipment such as grinding mills, cyclones, chutes, and conveyors are subjected to severe abrasive conditions from cement clinker, raw meal, and fly ash. The document provides practical insight into how overlay welding technologies are deployed to extend service life and reduce maintenance costs in the cement industry.

Core Technical Approach

The cement industry demands overlay solutions capable of withstanding high-temperature abrasive wear, often at temperatures between 100°C and 400°C, with impact energy from falling materials ranging from 5 to 20 J. The FLS approach typically involves multi-pass surfacing welds using hardfacing alloys applied via submerged arc welding (SAW) or shielded metal arc welding (SMAW) to base components made of low-carbon steel or low-alloy steel. The overlay design philosophy focuses on achieving a balance between hardness (typically 55-65 HRC for the overlay surface) and toughness to resist both abrasion and impact damage.

Typical Hardfacing Alloy Selection

Process Parameters and Deposition Strategy

The cladding process typically employs a multi-layer strategy: a transition layer is first deposited to dilute carbon and prevent intergranular cracking in the base metal, followed by two to three overlay layers of hardfacing alloy. For SAW overlay, typical parameters include a current of 400-600 A, arc voltage of 28-35 V, and travel speed of 200-350 mm/min. The preheat temperature is maintained at 150-250°C to reduce residual stresses and minimize hydrogen-induced cracking risk. Post-weld heat treatment (PWHT) at 600-650°C for 2-4 hours is recommended for thick overlay builds exceeding 8 mm to temper the martensitic microstructure and reduce hardness-induced brittleness.

Common Defects and Countermeasures

Engineering Practice Integration

In cement engineering applications, the overlay design must account for the specific wear mechanism present. For grinding mill liners, the primary mechanism is abrasion at moderate impact energy, favoring high-carbon martensitic alloys with carbide reinforcement. For cyclone liners operating above 300°C, oxidation resistance becomes critical, and high-chromium alloys with 25-30% Cr are preferred to form a protective Cr₂O₃ scale. The service life improvement achieved through proper overlay design typically ranges from 3x to 8x compared to bare carbon steel components, depending on the operating conditions and alloy selection.

Key Reflections and Study Insights

The FLS technology represents a mature engineering approach that prioritizes reliability over exotic material solutions. The key lesson for practitioners is that overlay design in cement applications must be driven by a thorough understanding of the local wear mechanism rather than simply maximizing hardness. A hardness of 65 HRC provides no benefit if the overlay spalls due to thermal cycling or if the base metal cracks from excessive residual stress. The transition layer concept and PWHT protocol are not optional extras but essential elements of a robust overlay system. Furthermore, the economic justification for overlay welding in cement plants is compelling: the cost of overlay material and labor is typically less than 15% of the cost of replacing the entire component, making it one of the most cost-effective maintenance strategies available. Engineers should always perform a wear mechanism analysis before selecting overlay alloys, as the wrong alloy choice can lead to premature failure and higher total cost of ownership despite initial savings.