In modern cement plants, the Vertical Roller Mill (VRM) is a critical piece of equipment for raw material and coal grinding. Key wear components such as grinding rollers and table liners operate under extremely harsh conditions, including abrasion, erosion, impact loading, and elevated temperatures.
Over time, these components experience uneven wear, leading to reduced grinding efficiency, increased power consumption, and unplanned shutdowns. Hardfacing restoration has therefore become a cost-effective and reliable solution to extend service life and maintain stable mill performance.
At BCC, the VRM hardfacing process has been standardized and upgraded through POP – Powder Overlay Process, BCC’s proprietary core technology, enabling precise control of metallurgical properties and wear performance.
POP Philosophy in VRM Hardfacing
POP is not merely a welding method. It is a materials engineering philosophy based on:
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Tailored alloy composition for specific wear mechanisms
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Controlled ratios of alloying elements (Cr, C, Mo, Nb, V, etc.)
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Optimized carbide type, size, and distribution
Each hardfacing layer is designed as a specific “recipe”, matched to actual operating conditions — similar to how different broths are prepared for different types of Phở.
Standard VRM Hardfacing Procedure at BCC
Wear Assessment and Condition Analysis
- Measurement of roller and table liner geometry
- Identification of wear patterns (uneven wear, ridging, wave wear)
- Evaluation of operating parameters: material type, moisture, particle size, grinding pressure
This step is essential to determine the correct POP alloy system.
Surface Preparation
- Removal of contaminants (oil, grease, dust)
- Machining and removal of worn hardfacing layers
- Surface profiling to ensure optimal bonding
According to POP principles, surface preparation directly determines coating longevity.
Preheating – Applied Only When Required
Preheating is NOT universally applied.
It is performed only under the following conditions:
- The base material is cast steel
- A buffer layer (buttering layer) is required between the base metal and the wear-resistant overlay
Purpose of preheating:
- Reduce thermal gradients
- Minimize hydrogen-induced cracking
- Control residual stresses in cast steel substrates
For rolled steel or fabricated components, preheating is typically not required, provided the correct POP hardfacing system is used.
Buffer Layer Application (When Applicable)
For cast steel components:
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A ductile buffer layer is deposited first
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The buffer layer acts as a stress-absorbing transition zone
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It improves metallurgical compatibility between the base metal and the wear layer
This step is critical for long-term reliability in cast components.
Hardfacing With POP Technology Cored Wire
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Application of POP-designed flux-cored wires
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Controlled parameters:
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Heat input
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Deposition rate
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Dilution control
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Layer thickness
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POP ensures uniform carbide distribution, avoiding brittle clusters or excessive dilution.
Profiling and Shape Restoration
- Rebuilding the functional grinding profile
- Ensuring optimal material flow and contact pressure
- Reducing vibration and uneven wear during operation
Controlled Cooling
- Natural or insulated cooling depending on component size
- Stress relaxation
- Stabilization of microstructure
Inspection and Acceptance
- Visual inspection
- Hardness measurement
- Surface crack inspection
- Dimensional verification
Proven Performance in Cement Plants
BCC’s POP-based VRM hardfacing solutions have demonstrated:
- Extended maintenance intervals
- Reduced localized repair frequency
- Improved grinding stability
- Lower total lifecycle cost
Conclusion
By integrating POP – Powder Overlay Process into VRM roller and table liner restoration, BCC delivers not just hardfacing, but a controlled, engineered wear solution.
This approach allows cement plants to:
- Extend equipment life
- Reduce dependency on imported wear parts
- Maintain consistent mill performance under demanding conditions
