Laser Cladding of Wear and Corrosion Resistant Materials with A High Power Direct Diode Laser

Laser cladding is a material deposition technique that enables selective surface modification of a workpiece. A metallic or ceramic layer can be added locally to the surface of a workpiece to improve the hardness or corrosion resistance, for example, without changing the properties of the bulk material. Several tracks can be overlapped to cover a large area, and excess material can be removed by grinding or machining. Powder cladding offers the most versatility for controlling the geometry of the clad track and for depositing tracks on complex shapes. Successful case study results of several materials in laser cladding with a high power direct diode laser with a robot assisted system are presented, including Stellite 6 (CrCo alloy), Nistelle 625 (CrNi alloy) onto low-carbon steel and Mo on H13. Direct diode lasers offer numerous advantages over other lasers for cladding. The infrared wavelength of the diode laser is more readily absorbed by metals than the energy of CO2 or Nd:YAG lasers, so no absorptive coating is needed for the substrate. Furthermore, these lasers are suitable for cladding large areas due to their large spot sizes and nearly uniform intensity distribution. Tracks formed with the pre-placed powder method have a maximum thickness on the order of 1.5 mm, an average width of 8.5 mm, and less than 2% dilution for all but one case. Tracks formed with the blown-powder method have a maximum thickness on the order of 0.6 mm, an average width of 8.7 mm, and dilution of order 10% or less. In case of Mo cladding, a high Mo concentration of 76.7 wt% was achieved. Diode lasers offer nearly uniform laser intensity over a large laser spot. The resulting clad tracks show superior geometry and quality to clad tracks formed by a Gaussian laser beam.