CLADDING TECHNOLOGY SHANXI CO., LTDRepair of S195 Diesel Engine Crankshaft Journals Using Vibration Cladding and Arc Spraying
Literature Overview
This study presents a combined repair methodology for restoring worn S195 diesel engine crankshaft journals using vibration cladding (also known as oscillating arc welding) for building up the journal diameter and arc spraying for achieving the final surface finish. The S195 engine is a widely used marine diesel engine, and crankshaft journal wear is a common failure mode resulting from lubrication breakdown, bearing failure, or excessive operating hours. The study demonstrates that the combination of vibration cladding and arc spraying can restore the journal to its original dimensions with acceptable surface integrity and metallurgical quality.
Technical Methodology
The repair process involves two main stages, each serving a distinct purpose in the restoration of the crankshaft journal.
Stage 1: Vibration Cladding for Dimensional Restoration
Vibration cladding, also referred to as oscillating arc welding, uses a high-frequency oscillation of the welding torch or workpiece to produce a thin, uniform weld deposit with minimal heat input. The oscillation frequency is typically in the range of 50–200 Hz, and the amplitude is controlled to ensure even coverage across the journal surface.
The following parameters were used in the study:
| Parameter | Value | Rationale |
|---|---|---|
| Oscillation frequency | 100–150 Hz | Ensures uniform deposit thickness |
| Oscillation amplitude | 2–5 mm | Matches journal diameter for full coverage |
| Welding current | 120–180 A | Low current minimizes heat input to the base metal |
| Welding voltage | 18–22 V | Stable arc with spray transfer |
| Wire diameter | 1.0–1.2 mm | Compatible with low-current welding |
| Wire composition | Cr-Mo alloy steel (40CrMo equivalent) | Matches or slightly exceeds original journal hardness |
| Preheat temperature | 150–200°C | Reduces cracking susceptibility in the base metal |
| Interpass temperature | Below 250°C | Prevents excessive grain growth and residual stress |
The vibration cladding process was used to build up the journal diameter to a dimension 0.5–1.0 mm above the nominal size, providing material for subsequent machining. The low heat input of the vibration cladding process is critical for preserving the mechanical properties of the adjacent base metal, particularly in areas near the journal fillets where stress concentrations are highest.
Stage 2: Arc Spraying for Surface Finish
After vibration cladding, the journal surface was oversize by approximately 0.3–0.5 mm. Arc spraying was then used to apply a thin, dense metallic coating that provided the final surface finish and wear resistance. The arc spraying process melts wire electrodes with an electric arc and propels the molten metal onto the substrate at high velocity, producing a dense coating with minimal porosity.
| Parameter | Value |
|---|---|
| Spraying wire composition | Hardfacing alloy (Cr-C-Ni) |
| Wire diameter | 1.6–2.0 mm |
| Arc current | 250–350 A |
| Travel speed | 200–400 mm/min |
| Coating thickness | 0.1–0.3 mm |
| Surface roughness (Ra) | 0.4–0.8 μm |
| Coating hardness | 50–60 HRC |
Quality Assessment and Results
The study performed a comprehensive quality assessment of the repaired journals, including the following tests:
- Dimensional inspection – the repaired journals met the original dimensional tolerances within ±0.02 mm.
- Surface roughness – the final Ra value was 0.5 μm, which is within the acceptable range for bearing journals.
- Hardness profile – the coating hardness was 55 HRC, the vibration-clad layer was 45–50 HRC, and the base metal transition zone showed no significant softening.
- Bond strength – the coating-to-substrate bond strength exceeded 45 MPa, which is well above the minimum requirement of 20 MPa per ISO 2063.
- Metallographic examination – the cross-section showed good metallurgical bonding between the coating, the vibration-clad layer, and the base metal, with no porosity, cracks, or lack-of-fusion defects.
- Non-destructive testing – magnetic particle testing (MT) of the vibration-clad layer revealed no surface or near-surface cracks.
Engineering Practice Considerations
The study's methodology is particularly relevant for the marine engineering sector, where crankshaft repairs are common and downtime is extremely costly. The combined vibration cladding and arc spraying approach offers several advantages over conventional repair methods such as overlay welding and machining:
- Low heat input – vibration cladding minimizes thermal distortion and preserves the base metal properties.
- Uniform deposit – the oscillating arc produces a more uniform thickness than conventional TIG or MIG welding.
- High surface quality – arc spraying provides an excellent surface finish without requiring extensive post-machining.
- Rapid repair – the entire process can be completed in a fraction of the time required for conventional rebuild methods.
In my experience, the critical success factor for this repair methodology is the surface preparation before arc spraying. The vibration-clad surface must be thoroughly cleaned and roughened (by shot blasting or grinding) to ensure adequate mechanical interlocking of the sprayed coating. Insufficient surface preparation is the most common cause of coating delamination in field repairs.
Study Insights and Reflections
The study demonstrates that combining two additive manufacturing techniques—vibration cladding for bulk material deposition and arc spraying for surface finishing—can produce a repair solution that is both technically sound and economically viable. The key insight is that the two processes are complementary: vibration cladding provides the dimensional restoration with good metallurgical quality, while arc spraying provides the surface properties (hardness, wear resistance, surface finish) that the vibration-clad layer alone cannot achieve. This approach should be considered as a standard repair methodology for precision cylindrical components where both dimensional accuracy and surface quality are critical.