Quality Control of Cladding on Wear-Resistant Components for Cement Equipment

Literature Overview

This technical paper by Zhang Liguo and Zhong Libin from China National Materials International Engineering Corporation (Tianjin Branch) addresses the practical challenges of cladding quality control for wear-resistant components in cement manufacturing equipment. Published in New Century Cement Herald in 2014, the work reflects the industrial reality of maintaining and refurbishing critical cement plant components such as mill liners, kiln wear plates, and preheater tower internals. The significance of this work lies in its practical orientation, bridging the gap between academic overlay welding research and field-level quality assurance in a demanding industrial environment.

Process Selection and Application Scope

Cement equipment components subjected to severe abrasion from raw materials, clinker, and gypsum require periodic cladding or replacement. The primary cladding processes employed in cement plant maintenance include:

Component	Typical Wear Mechanism	Recommended Cladding Process	Overlay Material
Ball mill liners	Abrasion + impact	SAW or FCAW overlay	High chromium cast iron, martensitic stainless steel
Kiln wear plates	Abrasion + thermal cycling	ESW or SAW overlay	310SS, Ni-based alloys
Preheater tower internals	Abrasion + corrosion	GMAW or SAW overlay	309L/310SS
Fan impellers	Erosion	TIG or GMAW overlay	Stellite 6, Co-based alloys
Conveyor rollers	Abrasion	SAW overlay	High carbon martensitic steel

The selection of cladding process is governed by component geometry, production schedule constraints, and the required overlay thickness. For large flat or gently curved surfaces, SAW and ESW are preferred due to high deposition rates. For complex geometries such as impellers and cyclone internals, GMAW and TIG are more practical. The total cladding thickness typically ranges from 3-10 mm for mill liners and 2-5 mm for kiln wear plates, requiring multiple passes with careful interpass temperature management.

Quality Control Framework

The quality control approach described in this literature follows a systematic PDCA (Plan-Do-Check-Act) framework adapted to the specific challenges of cement plant maintenance welding. The Plan phase involves detailed assessment of the component condition, wear pattern analysis, and selection of appropriate overlay material and process parameters. The Do phase encompasses welding execution with strict adherence to qualified welding procedures. The Check phase includes both in-process monitoring and post-weld inspection. The Act phase involves corrective actions based on inspection results and lessons learned.

Key quality control checkpoints include:

Base metal preparation: Grinding to remove the worn surface, ensuring a clean, oxide-free surface with a uniform bevel geometry. The surface roughness should be controlled below Ra 12.5 μm to ensure proper fusion.
Preheat control: For high-carbon martensitic overlay materials, preheating to 200-300°C is essential to reduce residual stresses and prevent cold cracking. For stainless steel overlays on carbon steel substrates, preheat temperatures of 100-200°C are recommended.
Interpass temperature: Must not exceed 250°C for martensitic overlays and 150°C for austenitic stainless steel overlays to prevent excessive grain growth and sensitization.
Post-weld heat treatment: Stress relief at 550-650°C for 2 hours per inch of thickness for martensitic overlays; solution treatment at 1050-1100°C for austenitic stainless steel overlays where permitted.

Defect Identification and Root Cause Analysis

Using a 5W2H approach, the literature identifies common defects and their root causes in cement equipment cladding operations:

Defect	What	Where	When	Why	Who	How
Hot cracking	Cracks in weld metal	Overlay layer, hot pass	During welding	High sulfur/phosphorus in base metal, low dilution	Welder	Reduce sulfur, increase dilution
Cold cracking	Cracks at interface	Fusion line	1-24 hours post-weld	High carbon equivalent, hydrogen embrittlement	Welder	Preheat, use low-hydrogen consumables
Spalling	Overlay delamination	Overlay-base interface	During service	Excessive residual stress, poor fusion	Welder/Inspector	Stress relief, improve fusion
Excessive dilution	Reduced hardness	Overlay layer	During welding	High current, low travel speed	Welder	Adjust parameters, use back-plate
Undercut	Groove at weld toe	Overlay edge	During welding	Excessive arc energy, improper stick angle	Welder	Reduce current, improve technique

The FMEA (Failure Mode and Effects Analysis) approach is particularly valuable in this context. For each welding parameter, the potential failure mode, severity, occurrence, and detection ratings are assessed to prioritize quality control efforts. For example, excessive preheat temperature has a high severity rating (9) for martensitic overlays because it reduces hardness and wear resistance, but the occurrence rating may be low (2) if proper monitoring is in place, resulting in a risk priority number of 18, which falls in the acceptable range.

Engineering Practice and Field Lessons

The literature emphasizes several practical lessons learned from years of cement plant maintenance operations:

Field welding conditions are rarely ideal. Wind, vibration, and limited access require process flexibility and robust consumable selection.
The dilution problem is the most persistent challenge. Using a backing plate or applying a high-alloy first pass (such as 309L) followed by the final overlay material can effectively manage dilution.
Wear testing should be conducted on coupon samples welded under identical conditions to the actual component to validate overlay performance before full-scale application.
Post-weld inspection should include visual examination, magnetic particle testing for surface defects, and ultrasonic testing for subsurface discontinuities. Hardness testing at multiple locations provides a rapid assessment of overlay uniformity.

Summary

This literature provides a practical and comprehensive framework for quality control of cladding operations on cement equipment wear-resistant components. The integration of systematic quality management tools such as PDCA, 5W2H, and FMEA with metallurgical knowledge and field experience offers a replicable approach for other industrial maintenance operations. Engineers involved in similar applications should adopt this structured quality control methodology to reduce rework rates, extend component service life, and ensure operational safety in demanding industrial environments.