Hardfacing steel with nanostructured coatings of Stellite-6 by supersonic laser deposition

The ability to manufacture coatings is critical to engineering design. Many components require the application of additional layers toenhance mechanical properties and protect against hostile environments. Supersonic laser deposition (SLD) is a novel coating methodbased on cold spray (CS) principles. In this technique, the deposition velocities can be significantly lower than those required foreffective bonding in CS applications. The addition of laser heat energy permits a change in the thermodynamic experience of impactingparticles, thereby offering a greater opportunity for efficient bonding at lower velocities as compared with the CS process. The workreported in this paper demonstrates the ability of the SLD process to deliver hardfacing materials to engineering surfaces. Stellite-6 hasbeen deposited on low-carbon steel tubes over a range of process parameters to establish the appropriate target power and traversespeeds for the coating formation. The coating properties and parameters were examined to determine the primary characteristics andgrain structure size. Their morphology and performance were studied through optical microscopy, scanning electron microscope(SEM), X-ray diffraction, hardness measurements and wear testing. The results have shown that SLD is capable of depositing layers ofStellite-6, with properties that are superior to those of their conventionally manufactured counterparts.

Characteristics of Stellite 6 Deposited by Supersonic Laser Deposition Under Optimized Parameters

Stellite 6 powders were deposited on low carbon steel using SLD （supersonic laser deposition） under optimized parameters. The structure, line scan of elements and porosity of coating were examined and analyzed using SEM （scanning electron microscope）, OM （optical microscope） and XRD （X-ray diffraction）. The adhesion strength between coating and substrate was tested by PAT-ADHESION/TENSILE and E900STM adhesive. The results showed the deposition characteristics of optimized coating with N2 at a pressure of 3.0 MPa, a temperature of 450 ℃ and a laser power of 1.5 kW were compared with those of Stellite 6 coating deposited by the HVOF （high velocity oxygen fuel）.

Deposition Behavior at Different Substrate Temperatures by Using Supersonic Laser Deposition

The supersonic laser deposition （SLD） is a new fabrication process which combines the supersonic powder stream found in cold spray with laser heating of the deposition zone. Because of the instantaneity of particles impact, the deformation behaviors and the adhesion behaviors of particles impacted on the substrate by SI.D cannot be well investigated through experiments. Therefore, a finite elemen! model was developed to solve the problems above. Meanwhile, the heat effect of the substrate heated by laser was discussed. The effective plastic strain and the effec- tive stress between the particle and substrate at different laser preheal temperatures were studied. The results show that laser depositing temperatures of 1 000 and 1 100 ℃ on substrate would be the optimized for the bonding of parti- cles and substrate. In addition, the simulation results conformed to experimental results.