Laser engineered net shaping process for SAE 4140 low alloy steel

This paper presents the investigation of the macrostructure, microstructure, and solidification structure of two ferrous based materials produced by the LENS™ process. The material deposited and examined in this work was a SAE 4140 low alloy steel. The focus of this work is to (1) identify the solidification structure and measure the Dendritic Arm Spacing (DAS) to determine growth/cooling rates at the solid/liquid interface, (2) identify and quantify discontinuities in the build structure, and (3) examine the affect of solidification and thermal history on the sample microstructure to further the understanding of the LENS™ process.

► The solidification morphology was clearly observed as a cellular/dendritic. ► The microstructure is mixed consisting of ferrite, bainite and tempered martensite. ► Varying metal powder deposition rate shows more intense melting processes. ► Highly enhanced turbulence in melt causes non-uniform structural properties. ► Total surface heat flux becomes uniform resulting realistic molecular structure prediction.