活化剂和表面激光淬火对TC4钛合金低温包埋渗铝的影响

doi:10.13251/j.issn.0254-6051.2025.02.047

摘要/Abstract

摘要： 研究了活化剂和激光淬火前处理对TC4钛合金低温渗铝的影响。采用固体粉末包埋法对TC4钛合金基材进行(550~700) ℃×4 h渗铝,包括NH₄Cl、NH₄F、NaF三种活化剂条件下的渗铝,以及对TC4合金基材进行表面激光淬火后的渗铝。使用扫描电镜、能谱仪和X射线衍射仪分析了渗铝试样的截面形貌、元素含量和物相组成。结果表明,在700 ℃×4 h包埋渗铝时,采用NaF、NH₄F和NH₄Cl三种活化剂,可使TC4合金表层铝含量从约10.04%分别增加到11.56%、15.66%和16.96%,较基体中铝含量分别增加15.1%、56.0%和68.9%,NH₄Cl的催化促渗效果最佳,NH₄F次之,NaF的效果最差,该结果与热力学分析结论一致。当保温温度降低到600 ℃时,渗铝后试样表层Al含量几乎无变化;但对TC4合金基材进行表面激光淬火前处理,可以细化表层晶粒,促进低温渗铝。TC4合金经过表面激光淬火后,表层α-Ti相平均晶粒尺寸随着激光功率的增加而不断减小;当在功率240 W进行表面激光淬火时,α-Ti相平均晶粒尺寸相比淬火前减小47.9%;在该功率进行4次表面淬火后,α-Ti相平均晶粒尺寸相比淬火前减小68.6%;表层晶粒尺寸的减小,可促进合金表层Al含量从约10.04%增加到600 ℃×4 h渗铝后的15.54%。

关键词: 低温渗铝, 包埋渗, 激光淬火, 活化剂, TC4钛合金

Abstract: Effects of activators and surface laser-quenching pretreatment on low-temperature aluminizing of TC4 titanium alloy were studied. The solid powder pack cementation aluminizing of TC4 alloy was conducted between 550-700 ℃ for 4 h with three different activators of NH₄Cl, NH₄F and NaF, respectively, in the pack mixture, and the aluminizing of TC4 alloy substrate after surface laser-quenching was carried out. The cross-sectional morphology, element content and surface phase of the aluminized layers were analyzed by means of scanning electron microscope (SEM), energy dispersive spectrometer (EDS) and X-Ray diffractometer (XRD). The results reveal that the three activators, NaF, NH₄F and NH₄Cl, can make Al content increase from 10.04% to 11.56%, 15.66% and 16.96%, respectively, of the surface layer of TC4 alloy after 700 ℃×4 h pack aluminizing. Compared with the Al content of the substrate, it is increased by 15.1%, 56.0% and 68.9%, respectively. The catalytic permeation effect of NH₄Cl is the best, followed by NH₄F, and the effect of NaF is the worst. The experiment results and the thermodynamic analysis are coincident. When the holding temperature drops to 600 ℃, there is almost no change in the surface Al content of the specimen after aluminizing. However, surface laser-quenching pretreatment of TC4 alloy substrate can refine the surface grain size and promote low-temperature aluminizing. After surface laser-quenching of TC4 alloy, the surface average grain size of α-Ti phase decreases continuously with the increase of laser power. When surface laser-quenched under 240 W, the average grain size of α-Ti phase is reduced by 47.9% compared with that without laser-quenching, and after four times laser-quenching at this power, the average grain size of α-Ti phase can be reduced by 68.6% than that without laser-quenching. The reduction of grain size of α-Ti phase on surface layer can promote the diffusion of aluminum in the surface layer, of which the content increases from 10.04% to 15.54% after 600 ℃×4 h aluminizing.

Key words: low-temperature aluminizing, pack cementation, laser-quenching, activator, TC4 titanium alloy

中图分类号:

TG174.4

卢嘉成, 田晓东. 活化剂和表面激光淬火对TC4钛合金低温包埋渗铝的影响[J]. 金属热处理, 2025, 50(2): 292-297.

Lu Jiacheng, Tian Xiaodong. Effects of activators and surface laser-quenching on low-temperature pack aluminizing of TC4 titanium alloy[J]. Heat Treatment of Metals, 2025, 50(2): 292-297.

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