Quantitative research on microstructure and thermal physical mechanism in laser melting deposition for Invar alloy

Self Cite

Individually fabrication forged parts and then joining them together through Laser Melting Deposition (LMD) is a viable way for manufacturing large components. For investigating the effect of the grain morphology of LMD joint, two 80mm-thick Ti6Al4V plates are successfully manufactured using three different scanning speeds (10, 15, and 20 mm/s). It is essential for understanding the thermal behaviour of melt pool during LMD to improve process quality. This study focuses on the energy density of heat source and the direction of heat flux, analyzing the effect of thermal behavior on the grain morphology and dimension of deposition area, equiaxed crystal zone (EQZ) and the substrate. The macrostructure is evaluated in the different thermal condition and scanning speeds. An extremely fine equiaxed crystal was observed near the joint boundary with a high temperature gradient and cooling rate. The curve epitaxial growth of fine columnar crystal rather than along straight lines is induced by the direction of heat conduction near the joint boundary. However, the orientation angle of epitaxial growth of the coarse columnar crystal is the same as previous deposition layer at the center of deposition area. Given the effect of high heat accumulation and low temperature gradient during LMD, the dimension of columnar crystal is coarsen significantly at the center of deposition area.

Section: Introductionmentioning

confidence: 99%

Effect of thermal behavior on the grain morphology and dimension of 80-mm-thick Ti6Al4V plates joined by laser melting deposition

Lyu

Wang

et al. 2022

Self Cite

“…Zhan et al analyzed the effect of different process parameters on morphology of cladding layer and also quantified the microstructure and width of the HAZ for Invar alloy. Tarak et al [17] considered that the influence of technology parameters of subsequent cladding layers on the microstructure and mechanical behavior of cladding layers to select desired process parameters and characterize the influence. The results show that the microstructure of the top layer was equiaxed, while the near substrate zone was fine dendritic.…”

Section: Introductionmentioning

confidence: 99%

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

Zhu

Chang³

et al. 2021

Self Cite

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.

“…Laser additive remanufacturing technology, as an emerging repair technology, has the characteristics of low dilution rate, less porosity and crack defects, dense structure, rapid solidification, more cleanness, and a good combination of cladding layer and substrate [6][7][8]. Due to the above significant advantages, laser additive remanufacturing technology has been applied in such important fields as single crystal turbine blades [9], continuous caster lateral rolls [10], hydraulic piston rods [11], railway rails [12], and has achieved remarkable economic benefits.…”

Section: Introductionmentioning

confidence: 99%

Laser additive remanufacturing parameters optimization and experimental study of heavy-duty sprocket

Guo

Yue

et al. 2021

Experimental research on laser additive remanufacturing technology of heavy-duty sprocket was carried out. The influences of laser power, scanning speed and powder feeding rate on cladding height, cladding area, melting area and dilution rate were compared and analyzed. The prediction models of the combination of process parameters with the geometric characteristics of cladding layer and dilution were established. A multi-objective process parameter optimization model with the maximum cladding height and cladding area maximum, the minimum melting area and dilution rate as objective functions was established, and the model was optimized and solved based on MOPSO algorithm. The laser additive remanufacturing repairing experiment of damaged sprocket was carried out by using the optimal parameters combination, and the microstructure and mechanical properties of the repaired region were analyzed. The results show that the scanning speed and powder feeding rate are the main factors influencing the geometric characteristics and dilution of the cladding area, and the models have good prediction accuracy. The optimal process parameters (1150 W, 950 mm/min, 3.8 rad/min) obtained by MOPSO algorithm is adopted to repair the damaged sprocket. The repaired area without cracks and pores, the cladding layer shows good metallurgical bonding with the substrate and the microhardness is twice that of the substrate. The experimental results prove that the laser additive remanufacturing technology is feasible to repair the damaged heavy-duty sprocket and has a strong engineering application prospect.