Fabrication of High Chromium White Iron Surface Layers on Ductile Cast Iron Substrate by Laser Surface Alloying

摘要

High chromium white iron surface layers (HWSLs) have been produced on a ductile cast iron EN-GJS-700-2 substrate by diode laser surface alloying with a direct injection of a pure chromium powder into the molten pool. The main objective of this study was to investigate the effect of laser alloying parameters on the microstructural evolution in the HWSLs. The composition of the uniformly alloyed HWSLs contained up to 14.4 wt.% Cr. Both hypoeutectic and eutectic high chromium white iron microstructures were obtained. The type and morphology of eutectic carbides are affected by both the chromium concentration in the molten pool and the solidification conditions. With increasing chromium content, the fraction of eutectic regions in the hypoeutectic HWSLs increases and the eutectic carbides become progressively smaller. The rod-type morphology of the M7C3 eutectic carbides was dominant in the eutectic HWSLs. An average hardness of the HWSLs was influenced by the size of carbide precipitations, and was 675 HV and 650 HV for hypoeutectic and eutectic compositions, respectively.