Zhuojin Pipe Fitting Co., LtdEffects of Welding Materials on Microstructure and High-Temperature Performance of UMCo50 Overlay Welds
Literature Overview
This paper by Xiong Jiang, Xin Zhengqiu, Li Wenchao, Xue Haitao, and Tang Qiang, published in Hot Working Technology (Vol. 53, No. 21, 2024, pp. 130–136), investigates the influence of welding material selection on the microstructure and high-temperature performance of UMCo50 overlay welds. The work was motivated by the need to extend the service life of coal slurry feed combustion mixers in a CNOOC Huizhou petrochemical facility.
Core Technical Context
Coal slurry feed combustion mixers operate under extreme conditions:
- High temperature: 600–900 °C
- Corrosive environment: molten salts, sulfur compounds, alkali metals
- Abrasive wear: coal particles, ash
- Thermal cycling: start-up and shutdown cycles
UMCo50 is a cobalt-based overlay alloy (Co-Cr-W type) designed for high-temperature wear and corrosion resistance. The alloy contains approximately 50% Cr, 10–15% W, and balance Co, providing excellent resistance to high-temperature oxidation, molten salt corrosion, and abrasive wear.
The study compares UMCo50 with four alternative welding wires designed to optimize specific properties through compositional modification.
Welding Material Design
UMCo50 (Reference Alloy)
| Element | Co | Cr | W | C | Mo | Ni | Fe |
|---|---|---|---|---|---|---|---|
| Content (wt%) | Balance | 50 | 12 | 0.8 | 3 | 5 | < 5 |
Alternative Welding Wires
| Wire | Co | Cr | W | C | Mo | Mn | Si | Fe | Design Objective |
|---|---|---|---|---|---|---|---|---|---|
| UMCo50 | Balance | 50 | 12 | 0.8 | 3 | - | - | < 5 | Reference |
| Wire A | Balance | 45 | 15 | 1.0 | 2 | 1.0 | 0.5 | < 8 | Higher hardness, wear resistance |
| Wire B | Balance | 55 | 10 | 0.6 | 2 | - | - | < 3 | Higher oxidation resistance |
| Wire C | Balance | 48 | 14 | 0.9 | 2.5 | 1.5 | 0.8 | < 6 | Balanced properties |
| Wire D | Balance | 52 | 11 | 0.7 | 3.5 |