Effects of process parameters on dimensional precision and tensile strength of wax patterns for investment casting by selective laser sintering

Turbine blades,produced by the directional solidification(DS)process,often require high dimensional accuracy and excellent mechanical properties.A critical step in their production is the fabrication of wax patterns.However,the traditional manufacturing process has many disadvantages,such as long-term production,low material utilization rate,and the high cost of producing a complex-shaped wax pattern.Selective laser sintering(SLS)is one of the most extensively used additive manufacturing techniques that substantially shortens the production cycle.In this study,SLS was adopted to fabricate the wax pattern instead of the traditional manufacturing process.The orthogonal experiment method was carried out to investigate the effects of laser power,scanning speed,scanning space,and layer thickness on the dimensional precision and morphologies of the SLS parts.The SLS parts showed a minimum dimensional deviation when laser power,scanning speed,scanning space,and layer thickness were 10 W,3000 mm·s^(-1),0.18 mm,and 0.25 mm,respectively.In addition,the tensile strength and fracture morphologies were closely associated with the laser volumetric energy density(VED).The tensile strength reached a maximum when the VED was 0.0762 J·mm-3,with an evident brittle fracture morphology.The wax pattern manufactured in this way meets the accuracy and strength requirements for investment casting.This research offers a novel path for the production of wax patterns for complex-shaped turbine blades by SLS.

A model for simulation of recrystallization microstructure in single-crystal superalloy

In the present investigation, a coupled crystal plasticity finite-element(CPFE) and cellular automaton(CA) model was developed to predict the microstructure of recrystallization in single-crystal(SX) Ni-based superalloy.The quasi-static compressive tests of [001] orientated SX DD6 superalloy were conducted on Gleeble3500 tester to calibrate the CPFE model based on crystal slip kinematics.The simulated stress-strain curve agrees well with the experimental results. Quantitative deformation amount was introduced in the deformed samples of simulation and experiment, and these samples were subsequently subjected to the standard solution heat treatment(SSHT).Results of CA simulation show that the recrystallization(RX) nucleation tends to occur at the third stage of SSHT process due to the high critical temperature of RX nucleation for the samples deformed at room temperature. The inhomogeneous RX grains gradually coarsen and compete to reach more stable status by reducing the system energy.Simulated RX grain density decreases from 7.500 to1.875 mm,agreeing well with the value of 1.920 mmfrom electron backscattered diffraction(EBSD) detection of the experimental sample.