CLADDING TECHNOLOGY SHANXI CO., LTDRepair of S195 Diesel Engine Crankshaft Journal Using Vibration Cladding and Arc Spraying
Literature Overview
This 2005 paper by Hao Jianjun, Shen Yuzeng, and Ma Yuejin from the College of Mechanical and Electrical Engineering at Hebei Agricultural University, published in the journal Agricultural Machinery, presents a repair methodology for worn crankshaft journals on S195 diesel engines using a combination of vibration cladding and arc spraying techniques. The work addresses a practical and economically significant problem in agricultural machinery maintenance: the restoration of worn rotating components to serviceable dimensions without the need for complete replacement.
Core Technical Content
The S195 diesel engine is a widely used single-cylinder, four-stroke, water-cooled diesel engine in Chinese agricultural machinery. The crankshaft is one of the most critical components, and wear of the journal surfaces due to lubrication failure, contamination, or extended service beyond recommended intervals is a common failure mode. Traditional repair methods include grinding to an undersize diameter with matching undersize bearings, or welding repair followed by machining. The approach described in this paper combines vibration cladding for material buildup with arc spraying for surface finishing.
Vibration Cladding Process
Vibration cladding is a thermal spray process that uses a vibrating electrode to produce a high-velocity spray of molten metal particles. The process involves clamping a metal wire between two electrodes, one of which vibrates at a high frequency. The wire is fed through an arc gap, where it is melted and atomized by the interaction of the arc and the vibration. The resulting molten particles are propelled onto the substrate surface at high velocity, forming a dense, well-bonded coating.
| Parameter | Typical Range | Purpose |
|---|---|---|
| Wire feed speed | 0.5–2.0 m/min | Control coating thickness per pass |
| Arc current | 100–300 A | Ensure complete wire melting |
| Vibration frequency | 50–200 Hz | Optimize atomization and particle size |
| Standoff distance | 10–30 mm | Balance particle velocity and coating density |
| Substrate preheat | 150–300°C | Reduce thermal stress and improve bonding |
The vibration cladding process is particularly suitable for repair applications because it allows for localized material buildup on worn surfaces. The coating can be applied in multiple passes to achieve the required oversize dimension, and the process produces a coating with good metallurgical bonding to the substrate.
Arc Spraying for Surface Finishing
After the vibration cladding step, arc spraying is used to refine the surface finish and improve the coating properties. Arc spraying involves melting two metal wires simultaneously in an electric arc and atomizing the molten metal with a compressed gas stream. The resulting particles are deposited onto the substrate surface, forming a coating with a controlled thickness and surface roughness.
The combination of vibration cladding for bulk material buildup and arc spraying for surface finishing is a pragmatic approach to crankshaft journal repair. The vibration cladding provides the necessary oversize dimension with good bonding strength, while the arc spraying produces a smooth, dense surface suitable for bearing operation.
Material Selection
The selection of cladding materials is critical for the success of the repair. For crankshaft journals, the coating material must have:
- Adequate hardness and wear resistance to withstand bearing contact loads
- Good fatigue resistance to resist crack initiation under cyclic loading
- Compatibility with the base steel to avoid cracking during thermal cycling
- Sufficient toughness to prevent brittle failure
Commonly used materials for this application include low-carbon steel wires (such as 45 steel or 20 steel) for the vibration cladding step, which provide good bonding and dimensional buildup, and medium-carbon or alloy steel wires for the arc spraying step, which provide improved hardness and wear resistance.
Engineering Practice and Quality Control
The repair of crankshaft journals is a well-established practice in the maintenance industry, but achieving a reliable repair requires careful attention to process parameters and quality control. The following quality control steps are essential:
- Surface preparation: The worn journal surface must be thoroughly cleaned of oil, grease, and rust. Machining to expose fresh metal is often necessary to ensure good bonding. Surface roughness should be controlled to provide adequate mechanical interlocking.
- Preheating: The crankshaft should be preheated to 150–300°C to reduce thermal stresses and prevent cracking. The preheat temperature should be maintained throughout the cladding process.
- Coating application: Multiple passes should be applied to achieve the required oversize dimension. Each pass should be inspected for porosity, lack of adhesion, and surface defects.
- Post-deposition inspection: The coated surface should be inspected using magnetic particle testing (MT) or penetrant testing (PT) to detect cracks and other surface defects. Hardness testing should verify that the coating meets the required hardness specification.
- Machining and finishing: The coated journal should be machined to the final dimensional tolerance and surface finish requirements. The machining parameters should be optimized to avoid damaging the coating.
- Final inspection: The repaired crankshaft should undergo dimensional inspection, surface roughness measurement, and hardness verification before being returned to service.
Defect Analysis and Countermeasures
| Defect | Cause | Countermeasure |
|---|---|---|
| Poor adhesion | Inadequate surface preparation, insufficient preheat | Improve cleaning, increase preheat temperature |
| Cracking | Thermal stress, incompatible materials | Reduce thermal gradient, select compatible materials |
| Porosity | Contaminated wire, inadequate gas flow | Use clean wire, ensure proper gas supply |
| Excessive dilution | High current, low travel speed | Optimize process parameters |
| Surface irregularities | Unstable wire feed, vibration | Stabilize wire feed, control vibration frequency |
Study Insights and Implications
This research demonstrates the practical value of combining thermal spray processes for component repair. The vibration cladding and arc spraying combination offers a cost-effective alternative to complete crankshaft replacement, which is particularly important for agricultural machinery where operators often operate on tight budgets.
The work also highlights the importance of process optimization and quality control in repair applications. Unlike new manufacturing, where process parameters can be carefully controlled in a factory environment, repair work is often performed in field conditions with limited equipment and varying substrate conditions. The development of robust, flexible process parameters that can accommodate these variations is essential for reliable repair outcomes.
For engineers involved in maintenance and repair, this study provides a framework for evaluating the suitability of thermal spray processes for component restoration. The key considerations include the severity of wear, the availability of suitable spray materials, the required dimensional tolerances, and the expected service life of the repaired component.
In conclusion, the combination of vibration cladding and arc spraying for crankshaft journal repair represents a practical and effective approach to extending the service life of agricultural machinery components. The method offers significant economic benefits compared to replacement, while the quality control measures described in the study provide confidence in the reliability of the repair.