Wear Mechanism of Dust Collector Impellers and Anti-Wear Cladding Strategy

Literature Overview

The study by Peng Zhenwei, Liu Yongsheng, Wang Li, and Wang Zongyu, published in the Journal of Jiamusi University (Natural Science Edition) in 1999, addresses a practically significant problem in power plant dust collection systems. The authors investigate the wear mechanism of dust collector impellers and propose anti-wear cladding solutions. This work bridges materials science and power plant maintenance engineering, offering field-relevant solutions to a persistent operational challenge.

Core Technical Content

The dust collector impellers in coal-fired power plants are subjected to a combination of erosive wear, abrasive wear, and adhesive wear. The primary wear mechanism involves high-velocity particulate impingement at oblique angles, which causes material removal through ploughing and cutting mechanisms rather than simple fatigue. The authors identify that the impeller blade surfaces experience impact velocities ranging from 40 to 80 m/s, with particle sizes predominantly in the 20 to 150 micrometer range. The wear rate is significantly influenced by the kinetic energy of impacting particles, the angle of incidence, and the microstructural characteristics of the base material.

Wear Mechanism Analysis

The wear behavior of impeller blades can be categorized into three distinct regimes based on the kinetic energy of impacting particles. In the low-energy regime, micro-ploughing dominates and surface roughness increases without significant material loss. In the medium-energy regime, micro-cutting and micro-chipping become active, leading to progressive material removal. In the high-energy regime, brittle fracture and spalling occur, resulting in catastrophic wear. The authors emphasize that the microstructure of the base carbon steel or low-alloy steel is inherently unsuitable for prolonged exposure to such conditions, as the relatively soft ferrite-pearlite matrix offers insufficient resistance to particulate erosion.

Cladding Strategy and Process Selection

The authors recommend hardfacing cladding using either submerged arc welding (SAW) with flux-cored wire or gas metal arc welding (GMAW) with hardfacing wire. The key consideration is achieving a dilution rate below 30 percent to preserve the hard phase content in the overlay layer. For impeller applications, the cladding layer thickness is typically 3 to 6 mm, which provides sufficient material for the expected service life while maintaining reasonable weight and cost.

The dilution problem is particularly critical in this application because the base steel dilution introduces soft ferrite into the overlay, reducing the overall hardness and wear resistance. Process parameters must be carefully controlled: wire feed speed, travel speed, and heat input all influence the dilution ratio. A practical approach involves using a pre-deposition of a dilution-resistant alloy layer before applying the final hardfacing layer.

Engineering Practice Integration

In practical implementation at Jiamusi Power Plant, the cladding process was adapted for field application using portable GMAW equipment. The impeller blades were preheated to 150 to 200 degrees Celsius to minimize residual stress and prevent cold cracking. Post-weld heat treatment at 600 to 650 degrees Celsius for 1 to 2 hours was applied to relieve stresses and improve toughness of the overlay layer. The service life extension achieved was approximately 4 to 6 times that of the uncladded impeller, representing a significant reduction in maintenance downtime and spare parts cost.

Key Reflections and Study Insights

The fundamental insight from this work is that wear resistance in erosive environments cannot be achieved by simply increasing hardness; the microstructure must contain sufficient hard phases (carbides or borides) distributed in a ductile matrix to resist both material removal and crack propagation. The oblique-angle impact regime is particularly damaging because it maximizes the cutting component of the wear mechanism. Future work should explore laser cladding as an alternative process that offers lower dilution and better microstructural control, although the 1999 timeframe of this publication predates the widespread adoption of laser cladding in Chinese power plants.