Stress analysis and microstructure-property evaluation of grid-path wire arc additive repair grate plates

For the wire arc additive repair of high-chromium cast iron (HCCI) grate plates, a novel grid-based path planning method was proposed. The method employs the direct projection technique to generate surface meshes on the point cloud, followed by variable-attitude oscillatory filling. The low-carbon steel grid used during the repair effectively inhibits crack propagation in HCCI, preventing the spalling of the deposited metal. Comparative analysis of stress distributions among the zigzag, contour offset and grid path planning revealed that the grid path reduced peak stress and variance by 29.8 % and 9.6 %, respectively. The microstructure of the HCCI grate plate body consists of primary austenite and martensite. Martensitic transformation occurs at the interface between eutectic carbides and primary austenite, where lath martensite encapsulates the eutectic carbides. Both primary carbides and eutectic carbides exhibit a hexagonal close-packed structure with similar crystallographic characteristics. The M₇C₃ carbides formed a robust wear-resistant framework, preventing abrasive particles from penetrating the matrix and reducing continuous sliding on the wear surface. Primary austenite provided critical structural support, preventing carbide detachment and significantly improving the material’s wear resistance. At 750 °C, the wear rate of the deposited metal was measured at 2.02 %, while at room temperature, it was 1.46 %. Both rates were significantly lower than the 3.71 % wear rate of the deposited metal on the currently used grate plates. The wear surface of HCCI exhibits numerous plow grooves, microcracks, and carbide spalling, which generate abrasive particles and accelerate wear. The dominant wear mechanism is a combination of micro-cutting and fracture-induced spalling.