Characterization of Fe-Cr-Ni Alloys Produced by Laser Surface Alloying using Mixed Power Feed

Abstract

A screw fed, gravity flow, carrier gas aided powder delivery system was used to produce laser surface alloys using chromium and nickel powders on AISI 1016 steel. A 10 kW continuous wave CO₂ laser was used for alloying, at incident power densities up to 1.2 × 10¹⁰ W m⁻² and traverse speeds up to 0.03 m s⁻¹. Ten overlapped passes were used to make alloyed zones 0.05 m long by 0·015 m wide. Alloys with up to 80 wt-%Cr and 58%Cr + 26%Ni were obtained. Surface roughness and corrosion resistance measurements were made. The microstructure was characterized by transmission and scanning electron microscopy. Smoother surfaces were obtained by increasing traverse speed and beam diameter. Corrosion samples passivated spontaneously in a 3.5%NaCI solution in distilled water, but were susceptible to pitting corrosion when uneven su;faces were subjected to corrosion testing. Microstructures were highly refined with a high dislocation density. These results are related to process mechanisms. The reported method of powder delivery is versatile, flexible, and reproducible, and can be used to make useful alloys.