具有TRIP效应的高硼铁基耐磨合金的相关基础研究

High-boron wear-resistant alloy has been applied for some wear-resistant accessories in our country. Its uses have limitation in some industry areas because of low impact toughness and poor plasticity. Therefore, the correlative basic research is very important to break through the technical bottleneck in order to develop the high-boron wear-resistant alloy with low cost, reduction of precious alloy consumption. It is known that the TRIP effect make steels have excellent impact toughness and plasticity. Therefore in this project, Mn, Al and Si elements are chosen as main studied object, which was regarded as to play the key role in the TRIP effect. Basing on the known effects of the elements on the precipitation behavior of the hard phase, the stability of the meta-stable austenite phase and the alloy properties are at first studied after the alloy was treated by I-Q-P treatment. It is then investigated the TRIP behaviors under condition of impact abrasive wear and its effect on anti-wear properties of the alloys. The microstructure and phase of the alloys are characterized by TEM、SEM、XRD and EBSD, the mechanical properties and the wear-resistant property are measured according to the country standard. The theory of strengthening and toughening of the wear-resistant alloy is developed by the phase transformaition. At last, it will be revealed the effects of Mn, Si and Al element on the formation of the metastable austenite phase, the mechanical properties and the anti-wear properties in the alloys after I-Q-P treatment. A theoretical guidance for the new generation of wear-resistantr alloy will be provided by the project.

高硼耐磨合金在我国经济建设中已有应用，但由于塑韧性低而应用受限于一些工业领域。为了开发此高耐磨性、低成本、节约贵重合金资源的合金，进行相关的基础研究来突破其技术瓶颈变得尤为重要。值得注意的是TRIP效应使钢具有优异的塑韧性。因此，本项目选择钢中对TRIP效应起着关键性作用的Mn、Al和Si等元素作为研究对象，在已找出它们对高硼耐磨合金中硬质相析出行为影响的基础上，先研究这些元素对经过I-Q-P处理组织中亚稳奥氏体相的稳定性及其合金的性能影响规律，再研究合金在冲击磨粒磨损下TRIP行为及其对耐磨性能的作用。采用TEM、SEM、XRD和EBSD表征合金的组织与相，测定其力学性能和耐磨性能，发展该耐磨合金的相变强韧化理论，并揭示Mn、Si和Al等元素在I-Q-P处理的合金中对奥氏体演变、力学性能和耐磨性能的作用规律及机制，为研发新一代耐磨合金提供理论依据。

具有TRIP效应的高硼铁基耐磨合金熔炼后的凝固先是奥氏体枝晶结晶，再发生（Fe2B+奥氏体）共晶转变，形成先共晶枝晶+共晶的混合组织，为典型铸造合金组织。合金中Al和Si元素使枝晶组织心部有铁素体，也使残余奥氏体中无碳化物析出。Mn则使合金中铁基固溶体冷却转变马氏体，并稳定了残余奥氏体。合金组织表征采用TEM、EBSD、XRD、EPMA和其他常规组织分析手段，性能主要测试冲击功、耐磨性和硬度。第一性原理计算出合金Mn含量约2-4%wt对脆性相（Fe,Mn）2B晶胞性能有改善作用。铸态合金组织中有块状残余奥氏体，但因（Fe,Mn）2B硬度为HV1200-1800，其硬质使合金具有很高的耐磨性，铸态合金冲吸收能量小于2J，断口上分析出主要是（Fe,Mn）2B脆性断裂导致的。.配分热处理能改善合金韧性。将合金先在奥氏体和铁素体两相区加热，Mn向硼化物和共晶体中奥氏体富集，使合金共晶体中出现具有TRIP效应的残余奥氏体，能改善合金韧性，从而提出Mn配分热处理概念。系列高硼合金经I-Q-P或Q-P配分热处理，基体组织中残余奥氏体主要以薄板状形式存在，其量从约5%wt提高到约20%wt，从而提出共格相界面增强碳配分的论说：配分中（Fe,Mn）2B在组织是硬质骨架，造成马氏体与残余奥氏体受压应力，从而碳原子可快速通过有共格相界面，因而残余奥氏体富碳而稳定性好。薄板状残余奥氏体具有TRIP效应，因而合金冲击吸收能量提高到11J，磨损中残余奥氏体发生马氏体转变，能含住或支撑增强相，虽然其量增加使合金硬度下降HRC2-5，但耐磨性提高耐磨性提高约2倍，合金耐磨机理也有变化。合金的耐磨性是NM500耐磨钢的十倍多。