Wear Cladding Repair of Cane Mill Roller Journals in Sugar Factories

Overview and Industry Context

The cane milling process in sugar factories is a high-intensity mechanical operation where rollers undergo severe abrasive and adhesive wear from sugarcane fibers, sand particles, and moisture. Journal bearing surfaces on cane mill rollers are critical load-bearing components, and their failure leads to unplanned shutdowns, loss of crushing capacity, and significant economic impact. The literature studied focuses on the systematic approach to identifying journal wear mechanisms, selecting appropriate overlay materials, and executing repair procedures that restore dimensional accuracy and service life. This study note synthesizes the core technical content and reflects on its applicability to similar heavy-duty rotating equipment repair scenarios encountered in engineering practice.

Wear Mechanism Analysis

The primary wear modes on cane mill roller journals include three-body abrasive wear from entrained sand and cane fiber fragments, adhesive wear from metal-to-metal contact under high sliding velocity, and fatigue spalling from cyclic contact stresses at the bearing interface. A typical cane mill roller operates at rotational speeds of 20 to 40 rpm with radial loads reaching 150 to 350 kN per journal. The specific sliding distance accumulates rapidly, often exceeding 50,000 km over a single crushing season. Understanding these mechanisms is essential for material selection because each wear mode demands different tribological properties from the overlay layer.

Key Wear Parameters

Cladding Material Selection

The base roller material is typically medium-carbon steel such as 45 steel or 40Cr with a hardness of 200 to 250 HB. The overlay material must provide a hardness differential of at least 200 HV above the base to resist abrasion while maintaining adequate toughness to avoid cracking under thermal and mechanical cycling. The literature evaluates several candidate materials including high-carbon chromium steel (H13 equivalent), cobalt-chromium alloys (Stellite 6 type), and tungsten carbide composite powders. Each option presents a trade-off between hardness, crack resistance, and cost.

The study concluded that a two-layer approach is optimal for cane mill journals: a transition layer of Ni-Cr-Mo alloy to ensure good bonding with the base steel and reduce residual stress, followed by a functional layer of high-carbon chromium steel or Co-Cr alloy for wear resistance. This layered strategy addresses both metallurgical compatibility and surface performance requirements.

Welding Process Selection and Parameters

The repair process involves GTAW (TIG) surfacing or SAW (submerged arc welding) overlay, depending on the journal geometry and access constraints. For smaller journals (under 300 mm diameter), GTAW provides superior control over heat input and dilution. For larger journals with wider surfaces, SAW with a consumable flux provides higher deposition rates and better surface quality. The critical process parameters are summarized below.

GTAW Overlay Parameters

SAW Overlay Parameters

Pre-Weld Preparation

Surface preparation is critical for ensuring metallurgical bonding between the base material and the overlay. The literature emphasizes a systematic preparation sequence: first, remove all worn material, rust, and contamination using grinding or shot blasting; second, machine the surface to a flatness tolerance of 0.1 mm per 100 mm; third, create a groove profile with a 60° included angle to ensure adequate root penetration; and fourth, apply a local preheat using induction heating or flame heating to bring the entire weld zone to the specified preheat temperature. The FMEA analysis identified insufficient preheat as the highest-risk factor for repair failure, with a severity of 9 and occurrence rating of 6, yielding a RPN of 216.

Post-Weld Inspection and Quality Control

The overlay layer must be inspected for defects before the journal is returned to service. The inspection protocol includes visual examination (VT) for surface cracks and porosity, magnetic particle testing (MT) for subsurface cracks, and ultrasonic testing (UT) for internal porosity and lack of fusion. Hardness testing across the entire overlay surface verifies uniform microstructure, with a typical acceptance criterion of 450–650 HV for the functional layer. Dimensional inspection using a coordinate measuring machine (CMM) or dial indicator confirms that the journal roundness is restored to within 0.05 mm TIR.

Engineering Practice Insights

From a practical standpoint, the most significant challenge in cane mill roller journal repair is managing residual stress and distortion in a heavily stressed rotating component. The literature recommends a multi-pass welding strategy with alternating weld directions to minimize angular distortion. A typical repair involves 3 to 5 layers of overlay, with each layer having a single-pass width of 8 to 12 mm. The interpass temperature must be carefully controlled because overheating the base material softens the heat-affected zone (HAZ) and reduces the load-bearing capacity of the journal.

Another critical insight is the importance of post-weld stress relief. Without proper PWHT, residual stresses in the overlay layer can reach 200 to 400 MPa, which combined with operational cyclic loading, can initiate fatigue cracks at the overlay-base interface. The recommended stress relief treatment is a furnace anneal at 550 to 650 °C for 2 hours per 25 mm of thickness, followed by slow cooling in the furnace. For field repairs where furnace access is limited, local induction stress relief at 550 to 600 °C is an acceptable alternative, though it requires careful temperature monitoring to avoid localized overheating.

A notable case study from the literature involved a sugar factory in Yunnan Province where a 380 mm diameter mill roller journal was repaired using the described two-layer GTAW overlay technique. The repair restored the journal to original dimensions with an overlay thickness of 3.2 mm. After 18 months of continuous operation, the overlay showed only 0.3 mm of wear, representing a service life extension of approximately 10 times compared to the original uncladded journal. This case validates the effectiveness of the systematic approach described in the literature.

Summary and Reflections

The study of cane mill roller journal wear cladding repair reveals that successful restoration depends on a holistic approach integrating wear mechanism analysis, appropriate material selection, precise process parameter control, and rigorous quality inspection. The two-layer overlay strategy of a Ni-Cr-Mo transition layer followed by a high-hardness functional layer provides an excellent balance between bonding integrity and wear resistance. Engineers working on similar heavy-duty rotating equipment repairs should adopt the FMEA methodology to identify and mitigate high-risk process variables, particularly preheat control and interpass temperature management. The economic justification for overlay repair over replacement is compelling, with typical savings of 60 to 80 percent in material cost and a significant reduction in downtime. This approach exemplifies how systematic welding engineering can extend asset life and improve operational reliability in demanding industrial environments.