【摘要】：裂紋是激光選區(qū)熔化(SLM,selective laser melting)鎳基高溫合金最嚴(yán)重的缺陷之一,嚴(yán)重削弱了材料的力學(xué)性能。采用逐行掃描策略制備了Inconel 625合金試樣,利用掃描電子顯微鏡(SEM)、電子背散射衍射(EBSD)等檢測方法研究了裂紋微觀形貌、周邊元素和晶粒分布等。SEM結(jié)果顯示在常溫下成形件內(nèi)部形成大量細(xì)小裂紋,裂紋長度約100μm。裂紋形成的內(nèi)因是在快速凝固的過程中,由于Nb,Mo元素的局部偏析,形成(γ+Laves)共晶凝固。同時(shí)在脆性相Laves周圍形成應(yīng)力集中,導(dǎo)致沿著晶界開裂,SLM高凝固速率產(chǎn)生的殘余應(yīng)力是微裂紋產(chǎn)生的直接原因。通過基板加熱工藝減小熱殘余應(yīng)力,利用X射線測定了不同預(yù)熱溫度(150和300℃)下的殘余應(yīng)力值。結(jié)果顯示基板預(yù)熱降低了熱殘余應(yīng)力,并最終抑制了裂紋的產(chǎn)生,隨著溫度的升高,裂紋數(shù)量逐漸減少,在預(yù)熱溫度300℃時(shí)裂紋數(shù)量最少。
[Abstract]:Crack is one of the most serious defects in laser selective melting (SLM,selective laser melting) nickel base superalloy, which seriously weakens the mechanical properties of the material. The microstructure of Inconel 625 alloy was studied by scanning electron microscope (SEM), (SEM), electron backscattering diffraction (EBSD), etc. SEM results show that a large number of small cracks are formed in the forming parts at room temperature, and the crack length is about 100 渭 m. The internal cause of crack formation is the formation of (緯 Laves) eutectic solidification due to local segregation of Nb,Mo elements during rapid solidification. At the same time, stress concentration is formed around the brittle phase Laves, which leads to the crack along the grain boundary and the residual stress produced by the high solidification rate is the direct cause of the microcracks. The thermal residual stress was reduced by the substrate heating process. The residual stress values at different preheating temperatures (150 and 300 鈩，

本文編號：2203930