Effect of Cladding Speed on Cladding Forming Quality

Literature Overview and Fundamental Significance

Cladding speed is one of the most critical process parameters governing the forming quality of weld overlay layers. This study systematically investigates the influence of travel speed on bead geometry, dilution ratio, microstructure, and mechanical properties across multiple cladding processes including plasma arc, gas metal arc, and submerged arc welding. The research provides quantitative relationships between speed and quality metrics that are directly applicable to procedure development and production optimization. Understanding the speed-quality relationship is fundamental to achieving consistent overlay performance in both new fabrication and repair applications.

Core Technical Findings

The study demonstrates that cladding speed exerts a non-linear influence on overlay quality, with an optimal range that balances productivity against metallurgical performance. At low speeds, excessive heat input causes high dilution, coarse microstructure, and potential distortion. At high speeds, insufficient heat input leads to incomplete fusion, porosity, and poor bead profile. The optimal speed window is process-specific and depends on consumable type, base metal thickness, and required overlay thickness.

Bead Geometry vs. Speed Relationship

Travel Speed (mm/min)	Bead Width (mm)	Bead Height (mm)	Reinforcement Ratio	Dilution (%)
100	18.5	3.2	0.17	35–40
150	16.2	3.0	0.19	28–33
200	14.5	2.8	0.19	22–27
250	12.8	2.5	0.20	18–22
300	11.2	2.2	0.20	15–19
350	9.8	1.8	0.18	12–16
400	8.5	1.4	0.16	10–14

The optimal speed for most plasma arc cladding applications falls in the 200–300 mm/min range, where the dilution ratio is minimized while maintaining adequate fusion. Below 150 mm/min, the excessive heat input causes dilution to increase rapidly. Above 350 mm/min, incomplete fusion defects become prevalent.

Microstructural Response to Speed Variation

Speed Range	Microstructure	Grain Size	Hardness (HV30)	Cracking Tendency
100–150 mm/min	Coarse dendritic, coarse grain	80–120 μm	450–520	Low (slow cooling)
150–250 mm/min	Fine dendritic, moderate grain	40–70 μm	550–650	Low
250–350 mm/min	Very fine dendritic, fine grain	20–40 μm	600–700	Medium
350–450 mm/min	Mixed, possible incomplete fusion	Variable	400–550	High

Process-Specific Speed Optimization

Different cladding processes exhibit different optimal speed ranges due to their inherent heat input characteristics and arc behavior.

Process	Typical Speed Range	Optimal Speed	Heat Input (kJ/mm)	Max Dilution
Plasma arc (PTA)	150–400 mm/min	200–300 mm/min	0.5–1.5	15–25%
GMAW (short arc)	100–300 mm/min	150–250 mm/min	1.0–2.5	25–40%
GMAW (spray)	200–500 mm/min	300–400 mm/min	1.5–3.0	20–35%
SAW	50–200 mm/min	100–150 mm/min	3.0–6.0	30–50%
TIG	50–200 mm/min	80–150 mm/min	0.8–2.0	20–35%
Hot-wire TIG	100–300 mm/min	150–250 mm/min	1.0–2.5	15–25%

Defect Analysis and Speed Correlation

Defect Type	Speed Range Where Occurs	Mechanism	Prevention
Excessive dilution	<150 mm/min	Excessive heat input melts base metal	Increase speed, reduce current
Incomplete fusion	>350 mm/min	Insufficient arc penetration	Decrease speed, increase current
Porosity	>300 mm/min	Rapid solidification traps gas	Reduce speed, improve shielding
Crater crack	All speeds (end of bead)	High cooling rate at termination	Backfill, slow cooling
Hot cracking	250–350 mm/min	Rapid solidification, segregation	Reduce speed, control interpass temp
Distortion	<150 mm/min	Excessive thermal input	Increase speed, use backing plate

Engineering Practice Guidelines

For production cladding operations, the following speed selection guidelines are recommended:

Initial procedure development: Begin at the midpoint of the typical speed range for the selected process, then adjust based on bead geometry and dilution measurements.
Dilution control: For corrosion-critical applications requiring dilution below 20%, operate at the upper end of the optimal speed range (250–350 mm/min for plasma arc).
Thickness buildup: For multi-pass cladding, maintain consistent speed between passes to ensure uniform overlay composition. Speed variation between passes of more than 20% creates compositional banding.
Thermal management: At speeds below 200 mm/min, implement active cooling (water-backed plate or interpass cooling) to control interpass temperature and minimize distortion.
Productivity optimization: For non-critical wear applications where dilution of 25–35% is acceptable, speeds of 300–400 mm/min significantly improve productivity with minimal quality compromise.

Study Insights and Practical Implications

The cladding speed investigation reveals that this single parameter simultaneously controls dilution, microstructure, defect susceptibility, and productivity. The fundamental challenge is that the optimal speed for metallurgical quality often conflicts with the optimal speed for productivity. Engineers must make explicit trade-off decisions based on the criticality of the application. For nuclear, chemical, or offshore applications where overlay integrity is safety-critical, the lower speed range should be maintained even at the cost of productivity. For general industrial wear applications, the upper speed range provides acceptable quality at significantly improved throughput.

The study also highlights the importance of speed consistency within a single weld run. Speed fluctuations of even 10–15% create visible bead profile irregularities and compositional variations that can compromise the overlay's functional performance. Modern plasma arc systems with CNC torch control can maintain speed accuracy within ±2%, which is essential for high-quality production cladding. For manual operations, operator training and consistent technique are the primary means of speed control, and the acceptance criteria should be adjusted accordingly. The quantitative data presented in this study provides a solid foundation for developing site-specific speed guidelines that balance quality requirements against production constraints.