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, heat-affected zone (HAZ) width, ratio of the columnar crystal to the equiaxed crystal, and change of Fe content of the 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 the 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 the 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 the bottom along the direction of the centerline of the cladding layer.
Highlights
The laser cladding is an advanced additive fabricating technology
The content are as follow: (1) the transformation of grain size, heat-affected zone (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 microstructure of substrate was composed of singlephase austenite, whose grain size was small (Fig. 3(b))
Summary
The laser cladding is an advanced additive fabricating technology. The laser beam shines on and melts the particles and the surface of the substrate, and fuse them together. Dinda et al [16] analysed the structure and properties of cladding layer by optical microscope (OM), scanning electron microscope (SEM), X-ray diffraction and hardness test They found the microstructure of the cladding layer is columnar dendritic in nature, which grew epitaxially from the substrate. A quantitative research into the microstructure and thermal process of the cladding layers is essential to the investigation of the microstructure in laser cladding process, because it will provide significant reference for precise repair of Invar alloy mould. The content are as follow: (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 correlations between process parameters and microstructure characteristics of cladding layer are further established
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