硼化物层脆性的分析与控制

ANALYSIS AND CONTROL OF BRITTLENESSOF THE BORIDE LAYER

在试验研究结果和其他文献报道的基础上，综合分析和讨论了硼化物层的系列致脆因素。据此，提出了若干减脆措施。添加氮，某些过渡或稀土金属元素能有效减小硼化物层的本征脆性。这归因于硼化物层，主要由Ｆｅ＿２Ｂ相构成，并伴有少量分散的第二相质点，且用化物层晶界结构得以改善，其组织不仅细化且致密。依靠钢号的精选亦能改善共渗钢件基体与过渡层的显微组织，可减轻硼化物的生长织构，减小共渗层的表现脆性。靠工艺材料的净化也能控制硼化物层的表观脆性。通过多元渗硼与后继热处理工艺参数的优化亦可减小表现脆性。此外，对硼化物层脆性测试方法亦作了评述。为正确评价硼化物层的脆性，推荐了几种实用的测试方法。

Based on our experimental results and those reported in the literature, a num-ber of factots which cause the brittleness of the boride layer on steel are analyzed anddiscused. Furthermote, some methods to alleviate the brittleness of boride layer areproposed as follows. Introducing such elements as nitrogen, some transition or rare earthmetals can effectively decrease the intrinsic brittleness of the boride layer. This can beattributed to the following reasons. The structure of the boride layer is mainly composedof Fe2B phase, along with a small amount of dispersed second phase particles. the grainboundary structure of the boride layer is improved. The structure of the boride layet be-comes not only fine but also compact.The microstructure of the core matrix and thetransition layer of a co-penetrated steel part can be improved by selecting the type ofsteels. also, the growth texture of tke boride phase can be alleviated. Thus, the apparentbrittleness of the co-penetrated boride layer can be decreased. The apparent brittleness ofthe boride layer can be controlled by the purification of the technical materials used,too. The apparent brittleness can be lessened by optimization of the polybasic boronizingparameters and the parameters of the post-heat treatment. In addition, the measuringmethods for boride layer brittleness are reviewed. Several practical useful measuringmethods are recommended in order to evaluate correctly the apparent brittleness of theboride laver.