Laser hot-wire cladding of Co-Cr-W metal cored wire

Abstract

Laser hot-wire cladding (LHWC) is a hybrid deposition process where the wire is preheated by resistant heat during the deposition process. This process can dramatically increase the deposition efficiency and the material utilization rate. In this study, a cobalt-based metal cored wire was deposited by using laser hot-wire cladding. The CMOS camera assisted by a green laser illumination was used to monitor the stability of the deposition process and to investigate the molten pool width and length. The effects of processing parameters such as wire feed rate and scanning speed on the clad geometrical characteristics (height, wetting angle, and dilution rate) were studied in detail. The variation of the secondary dendrite arm spacing (SDAS) and microhardness with different processing parameters was discussed. The microstructure and corrosion resistance of the deposited alloy were finally analyzed. It was found that the resistant heat applied on the wire was a dominate factor influencing the stability of the deposition process. The clad height could be predicted by measuring the molten pool width. The molten pool length could be used as an indicator to reflect the cooling rate of the process. The clad height, wetting angle, and dilution rate were all sensitive to the wire feed rate and the scanning speed. The microhardness was mainly determined by the dilution rate. A high dilution rate decreased the clad hardness. The microstructure of the deposited alloy had a typical hypo-eutectic structure. An improved corrosion resistance of the deposited coating was obtained when compared to the substrate.