Study On Selective Laser Melting Processing And Properties Of FeCrAl Alloy

Selective Laser Melting(SLM),as one of the most important additive manufacturing technologies,has been widely used in the research and application of additive manufacturing of metal materials such as aluminum alloys,iron alloys,and titanium alloys.FeCrAl alloy has the advantage of low temperature coefficient of resistance,high thermal stability,low density,high oxidation resistance,and low price.In terms of industrial application,the use of FeCrAl alloy to make the honeycomb structure catalyst carrier of automobile exhaust gas purifier is considered to be the most promising metal carrier.Up until now,research about additive manufacture and related material development for FeCrAl alloy has rarely been reported and this alloy has drawn little attention in the field of additive manufacture.This study is focused on the application of FeCrAl alloy in automobile exhaust purifier carrier.By choosing selective laser melting(SLM)as the main technology,this study constructed the relationship modeling between SLM processing parameters and relative density of Fe20Cr5Al alloy through systematic central composite design(CCD),and optimized the SLM processing parameters thereafter.Two heat treatment processes,including annealing at850?for 1 hour and quenching upon soaking at 1150?for 1 hour,have been made to SLM processed Fe20Cr5Al alloy.The effects of heat treatments on microstructure and mechanical properties of Fe20Cr5Al alloy were investigated to reveal the influencing mechanisms.The high temperature oxidation test was made to SLM processed Fe20Cr5Al alloy to evaluate the oxidation resistance of this alloy.The thin-walled honeycomb structure of Fe20Cr5Al alloy was prepared by SLM,and precious metal catalyst was deposited on the honeycomb carrier by electroless plating.The exhaust purification performance was tested.It is found that:(1)Based on CCD,the relationship modeling between SLM processing parameters(laser power P,W,scanning speed V,mm/s,and hatch spacing h,mm)and the relative density(RD)of Fe20Cr5Al was constructed as:RD=-0.5067485+0.004296*P+0.000242*V+21.994799*h+6.76187*P*V-0.00409*P*h-0.00422*V*h-0.000008*P~2-6.97095*V~2-115.4205*h~2The optimal SLM processing parameters per this model include laser power 310 W,scanning speed 1500 mm/s,and hatch spacing 0.06 mm.The relative density via the optimal SLM processing parameters can reach 98.6%.(2)Hardness testing for SLM processed Fe20Cr5Al before and after heat treatments shows that there is no noticeable hardness difference between horizontal cross-section and vertical cross-section and therefore no apparent hardness anisotropy.Two heat treatments apparently reduce the hardness of SLM processed Fe20Cr5Al.Annealing at 850?for 1 hour reduces the hardness on horizontal cross-section from HV269 to HV254 and the hardness on vertical cross-section from HV251 to HV238.And more noticeably,quenching upon soaking at 1150?for 1 hour reduces the hardness on horizontal cross-section to HV238 and the hardness on vertical cross-section to HV234.(3)Tensile test shows that for SLM processed Fe20Cr5Al,UTS is 824.8 MPa and elongation is 12.3%.Two heat treatments reduces the UTS but increases the elongation.Annealing at 850?for 1 hour reduce the UTS to 802.3 MPa and increase the elongation to20.5%.Quenching upon soaking at 1150?for 1 hour reduces the UTS to 725.6 MPa and increases the elongation to 16.7%.(4)For SLM processed Fe20Cr5Al,oxidation test at 800?shows no mass increase and oxidation test at 1000?shows the oxidation rate is 0.042 g/m~2·h.(5)Exhaust purification test shows that the Pd/FeCrAl honeycomb catalyst prepared by chemical plating in this study has low conversion rate for NO but the good purification result for methylbenzene,which is close to the commercial Pd/Cordierite catalyst.