The Twin Wire Arc Spray process is an automated system for depositing a molten, high performance metal coating on the base metal of pressure vessels, boiler firesides, fan blades, piping, and turbine parts subject to corrosion and erosion. The inconel materials, with high nickel, high chrome matrix content are selected not only for corrosion and erosion properties, but also for thermal expansion, matching it to carbon steel. The resulting coating provides and excellent barrier layer to protect the surface from further deterioration. Table 1 compares characteristics of the Twin Wire Electric Wire Arc spray process with other field repair technologies including flame spray coatings and weld overlay. The Twin Wire Arc spray process exhibits superior mechanical bond strength and coating density than flame spray and unlike weld overlay has no heat affected zone (HAZ).
| Classifications | Wire Arc Sray | Flame Spray | Weld Overlay |
|---|---|---|---|
| Bond Type | Mechanical | Mechanical | Metallurgical |
| Bond Strength (PSI) | 5000 – 7000 | 2500 – 4000 | 60,000+ |
| Density (%) | 88 – 95 | 70 – 90 | ~100 |
| Deposit Rate | High | Medium | Low |
| HAZ | None | None | Yes |
| Substrate Temp (oF) | 125 – 175 | 200 – 275 | Full Base Metal |