Eliminating Cladding Cracks: Pre-Heating and Stress Analysis

摘要

Laser cladding, as a surface modification or a rapid prototyping tool, has great potential in manufacturing industry. However, clad layers often have large thermal and/or phase transformation stress that may cause fracture. Due to this reason, selection of cladding materials has been limited. It further restricts functionality of a laser-clad component. A systematic study in material-process-stress relation has been conducted. Tool steel powder H13 and micro-melt 10V (MM10) were chosen as cladding materials. Low alloy steel 4150 was used as a substrate material. Induction pre-heating is applied to reduce cooling rates. Three patterns, single bead, intersection of two beads and pad consisting of 9 parallel beads, were generated for stress analysis. The difference induced by pre-heating process is significant. Laser cladding of these materials can be done without any micro-cracks if a pre-heating process is employed. Cladding stress in each bead was measured via x-ray diffraction method. Effect of the preheating process on wear resistance of cladding material was investigated. Fracture mechanism is discussed and proposed.