交流电场增强45钢中温粉末法硼铝共渗特性

为克服传统粉末法硼铝共渗存在的处理温度高、渗速慢以及渗剂利用率低的缺点,研究以交流电场加速中碳 45 钢中温粉末法硼铝共渗。 分别采用光学显微镜、X 射线衍射仪、扫描电镜能谱仪和显微硬度计等观测共渗层厚度、组织、相结构、成分分布及硬度分布,研究电场对共渗的影响,分析硼、铝的交互作用。 研究发现:交流电场对硼铝共渗的促进程度与渗剂配比有关;当渗剂中铝粉的质量分数低于 3%时,共渗以渗硼为主,共渗层组织主要为表层含铝的锯齿状硼化物,铝促进硼化物生长,在施加交流电场时表现更为显著,当电场电流为 2 A 时,铝的促渗作用在铝粉的质量分数为 2%时达到峰值,渗层厚度约为相应不加铝粉的 3 倍,而当电场电流增至 6 A 时,渗层厚度约为相应不加铝粉的 10 倍, 增加电场电流会增加渗层次表层的硬度;当渗剂中铝粉的质量分数≥3%时,共渗以渗铝为主,渗层组织表现为渗铝特征,但渗层厚度远比相应单一渗铝的薄,交流电场的促渗作用不显著。

Characterization of Alternating Current Field Enhanced Pack Boron-Aluminizing at a Medium Temperature for 45 Steel

Alternating current field (ACF) enhanced pack boron-aluminizing (PBA) at a medium temperature for medium carbon 45 steel was studied to overcome the drawbacks of high treating temperature, slow diffusiong speed and low utilization of pack media in conventional PBA. The thickness, microstructure, phases, element distribution and hardness distribution of the coating were revealed with optical microscope, X-ray diffractormeter, energy dispersive specmeter in a scanning electron micro- scope and micro-hardness tester, respectively. The effects of the ACF on PBA were studied, and the interaction of boron with a- luminium during the PBA was analyzed. Results show that the promotion of ACF on PBA is related to the ratio of the pack media. When the content of Al powder in the pack media is less than 3%, boriding is predominant in coating. Boride with saw- tooth morphology is predominant in the PBA case, in the surface layer of which Al dissolves. The Al powder in the pack media promotes the PBA, especially when an ACF is applied. When a 2 A ACF current is applied, the promotion to PAB is maximized by employing 2% Al. The coating thickness is about three times as thick as the case obtained without employing Al powder. While when the ACF current is increased to 6 A, the coating thickness is about ten times as thick as the case obtained without employing Al powder. The hardness of the subsurface is increased with the increase of the ACF current. When the content of Al powder in the pack media is more than or equal to 3%, aluminizing is predominant in the PBA. The PBA case shows a feature of aluminizing, while its thickness is much thinner than that by corresponding single aluminizing. And the enhancing effect ofACF for producing such case is not remarkable.