功率对激光熔化沉积FeCrW系ODS钢微观组织与力学性能的影响

Effect of power on microstructure and mechanical properties of FeCrW ODS steel deposited by laser melting

采用增材制造方法分别在600、800和1000 W激光功率下直接熔化沉积制备FeCrWYAl系ODS不锈钢单壁件,研究了激光功率对ODS不锈钢件微观组织和性能的影响,以期获得相对更好的激光功率参数;并在该激光功率下,分别制备了FeCrWY和FeCrWAl合金单壁对比件,讨论微合金元素Al和Y对激光熔化沉积单壁件显微组织的影响。采用扫描电镜(SEM)和能谱(EDS)等对开裂单壁件的断口组织进行表征和分析,讨论了其断裂机制,并采用维氏硬度计测量了合金的显微硬度。结果表明:随着激光功率的提高,合金试样的组织更粗大、开裂更严重;合金元素Y和Al的添加使得合金开裂更严重,合金试样的开裂与凝固末期产生的结晶裂纹有关,为热致裂纹。断口组织分析表明,合金试样平行沉积方向为沿晶开裂,晶界处的氧元素偏析及细小的钨的碳化物相所导致的柱状晶晶界弱化可能是合金试样沿沉积方向贯穿开裂的重要原因之一。随着激光功率的下降,合金试样的硬度下降,但组织较为均匀;不同功率制备的FeCrWYAl和FeCrWAl样品组织均为单相铁素体组织,而600 W制备获得的FeCrWY样品组织为铁素体/马氏体双相组织。

FeCrWYAl ODS stainless steel thin-wall parts were prepared by direct melting deposition at laser power of 600 W,800 W and 1000 W,respectively. The effect of laser power on microstructure and mechanical properties of the ODS stainless steel parts was studied in order to obtain relatively better laser power parameters,and FeCrWY and FeCrWAl alloy thin-wall parts were prepared at this laser power, respectively,and the effects of microalloyed elements Al and Y on the microstructure of the thin-wall parts deposited by laser melting were discussed. The fracture structure of cracked thin-wall parts was characterized and analyzed by scanning electron microscopy ( SEM) and energy dispersion spectrum ( EDS),and the fracture mechanism was discussed. The microhardness of the alloy samples was measured by Vickers hardness tester. The results show that with the increase of laser power,the microstructure of the alloy samples is coarse and the cracking is more serious,and the addition of alloy elements Y and Al makes the cracking of the alloy samples more serious,and the cracking of the alloy samples is related to the crystallization crack at the end of solidification,which is a thermal crack. The fracture microstructure analysis shows that the parallel deposition direction of the alloy samples is intergranular cracking,and the segregation of oxygen elements at the grain boundary and the weakening of columnar grain boundary caused by the fine WC carbide phase may be one of the important reasons for the penetration cracking of the alloy samples along the deposition direction. With the decrease of laser power,the hardness of the alloy sample decreases,but the microstructure is more uniform. The microstructure of the FeCrWYAl and FeCrWAl samples prepared at different laser powers is single-phase ferrite structure,while the microstructure of the FeCrWY sample prepared at laser power of 600 W is ferrite /martensite dual-phase structure.