EFFECTS OF B4C AND CR3C2 ON MICROSTRUCTURE AND PROPERTIES OF LASER CLADDING CO-BASED ALLOY COATINGS

Based on the background of automotive mold surface strengthening, the effects of three different enhancements on the microstructure evolution, micro-hardness and wear resistance of laser cladding cobalt-based coatings were studied. The three reinforcing materials were Co45 alloy powder, Co45/8% B4C mixed powder and Co45/8% B4C/5% Cr3C2 mixed powder. They were respectively used to conduct laser cladding on the surface of die steel with preset powder method, with laser power of 2000W and scanning speed of 4mm/s. According to the test results, the hardness and wear resistance of the cladding coating were the best when Co45/8% B4C powder was added. In addition, the study also found that B4C reacted with Cr3C2 during laser cladding to eventually generate Cr2B. The CrB2 generated for the first time during the reaction was transformed into the most stable Cr2B with an orthorhombic Fddd symmetry due to its poor stability. Therefore, the sample with Co45/8% B4C/5% Cr3C2 mixed powder was affected with a slight decrease in microhardness and wear resistance.