Microstructure evolution mechanism of single and multi-pass in laser cladding based on heat accumulation effect for invar alloy

Abstract

This work explores how the process parameters in laser cladding affect the evolution of the microstructure of the single pass and multi-pass cladding layers of Invar alloys. The research examined the cladding layers from three aspects: (1) the transformation of grain size, HAZ width, ratio of the columnar crystal to the equiaxed crystal, and change of Fe content of cladding layer; (2) the effects of heat accumulation on grain size, HAZ width and remelting zone; and (3) the hardness distribution of single pass and multi-pass cladding layers. The investigation has the following four findings: (1) the cladding layer is composed of equiaxed crystals at the top and columnar crystals at the bottom of cladding layer; (2) the processing parameters have significant effects on the width of the HAZ, proportion between the columnar and equiaxed crystals and the change of Fe content of cladding layer.(3) the gradual accumulation of heat causes the increase in HAZ width, the grain size, and the area of the remelting zone; and (4) the hardness progressively reduces from the top to bottom along the direction of the centerline of the cladding layer.