等离子束硬化工艺参数对硼铸铁硬化轨迹交叉点的组织与硬度的影响

研究了等离子束表面硬化工艺参数对硼铸铁硬化轨迹交叉点处硬化层的组织与硬度分布的影响。试验结果表明，交叉点处硬化层的组织为隐针马氏体 残留奥氏体 片状石墨 硼化物，其硬化层的深度和硬度均高于单道硬化层的深度和硬度。交叉点处硬化层中的最高硬度并未出现在最表面，而是发生在距表面有一定距离的次表层；且随电流增加，最高硬度的位置向硬化层内部推移。硬化层中硬度分布很不均匀，其最高硬度两侧均具有较大的硬度梯度，但随电流增大，硬度梯度减小。

Effect of Plasma Beam Surface Hardening Parameters on Microstructure and Hardness of Boron Cast Iron at Junction of the Two Hardening Traces

Effects of plasma beam surface hardening parameters on microstructure and hardness distribution of the hardening layer of boron cast iron at junction of two hardening traces were investigated.Experimental results show that the microstructure in the junction of hardened layers consists of cryptocrystalline martensite,retained austenite,flake graphite and boride,and its hardness and depth are higher than those in the single hardening trace.The highest hardness in junction of hardened layers does not present at the top surface,but at the sub surface in certain distance from the surface.The position where the highest hardness appears moves towards inside along the depth of hardened layer with increase of the electrical current.The hardness distribution is obviously non-homegeneous in hardened layer,the hardness gradient in both sides of top hardness is steeper,and reduces with increase of the electrical current.