Laser Cladding of Two Hardfacing Alloys Onto Cylindrical Low Alloy Steel Substrates With a High Power Direct Diode Laser

Abstract

Blown-powder laser cladding is an efficient method for enhancing the surface properties of engineering components while preserving the properties of the base material. High power direct diode lasers (HPDDLs) offer wide beams with nearly uniform intensity distribution, allowing the deposition of wide clad tracks with flatter profiles than those produced with a Gaussian beam. In this work, a 4.0 kW HPDDL is used to perform blown-powder cladding on AISI 4140 and AISI 5150 steel shafts. The first part of the experiments concerns two-layer circumferential tracks created from two commonly used hardfacing alloys: Stellite 6 (Co-Cr alloy) and Nistelle 625 (Ni-Cr alloy). The effects of laser power and powder feed rate on the clad geometry are assessed. Increasing the powder feed rate and holding constant all other parameters decreases the track width-to-thickness aspect ratio. All tracks exhibit dendrite microstructures that are characteristic of powder-based clad tracks. The tracks exhibit no cracks or porosity. Energy dispersive X-ray (EDX) analysis reveals dilution of five percent or less between the clad and substrate materials. The second part of the experiments concerns overlapping of single-layer clad tracks in a continuous helical pattern on the substrate to form a layer that covers a large area. Clad layer thickness and inter-track porosity are measured to determine the optimum degree of overlap for producing a high-quality clad layer. The thickness of the resulting Stellite 6 and Nistelle 625 clad layers decreases as the overlap percentage decreases. No inter-track, interfacial, or bulk pores are present for any tests, comprising overlap percentages of 50% and lower.