合金铸铁光束相变硬化层的组织和硬度

采用５ｋＷ光束加热设备对珠光体合金灰铸铁进行了表面相变硬化处理。研究了相变层的组织和硬度特征，以及光束能量参数对相变层组织和硬度的影响规律。实验结果表明，合金铸铁光束表面相变硬化层由与基材相邻的不完全相变区及表面完全相变区组成。完全相变区的组织是马氏体，随能量密度提高马氏体针片尺寸增加，硬度降低。不完全相变区是残余珠光体与托氏体型珠光体的混合组织，其硬度较完全相变区显著下降。采用光束相变硬化处理可在灰铸铁表面获得深度 ０．２ｍｍ以上，硬度近 ９００ｋｇ／ｍｍ２的强化层。

Microstructure and Hardness of strengthened Layer in Light Beam Hardening of Alloying Cast Iron

Surface hardening of alloying gray cast iron with pearlite microstructure by using 5kW light beam heating equipment has been performed. The microstructure and hardness of the transformation layer and the effect of light beam energy parameters on them have been studied. The experimental results show that the surface hardened layer consists of non-full transformation area which is adjacent to the base metal and surface full transformation area. The microstructure of full transformation area is martensite. As the light energy intensity increases,the acicular size of martensite increases,and the hardness decreases. The microstructure of non-full transformation area is the mixture of residual pearlite and troostite - type pearlite, and the hardness is largely lower than that of full transformation area. A strengthened layer with more than 0. 2mm depth and near 900kg/mm~2 hardness can be obtained on the surface of gray cast iron by light beam hardening.