Microscale Clad Thickness Measurement after Laser Cladding via Laser Speckle Photography

Abstract

Laser cladding is a promising technique that has been used for surface modification. It uses a high-power laser to melt a deposited powder and a thin layer of a substrate forming a hard coating with a certain thickness according to the laser cladding process parameters. Conventionally, the thickness of the deposited layer is measured by means of an optical microscope. The application of Laser Speckle Photography (LSP) for determining the thickness of the formed layer is an innovative technique of such technology used primarily for material surface topography investigation. LSP is a low-cost, non-destructive and non-contact optical imaging technique that can gather highly significant information about the monitored object. In this study, the laser cladding process was performed by the deposition of 60% tungsten carbide particles (WC) plus 40% nickel-based alloy (NiCrBSiC) powder blend on Ti6Al4V titanium substrate. A continuous Nd:YAG laser system attached with a coaxial cladding nozzle was used to perform the clad layer. Different laser processing parameters were carried out to reach the optimum conditions for favorable mechanical properties. The LSP findings were verified by the experimental results. The results proved the ability of LSP to measure the layer thickness of the samples with high accuracy. It was indicated that the laser scanning speed has a significant impact on the obtained layer thickness than the laser power, taking into account the fixed of all other processing parameters.