Surface Spectroscopic Studies of High-Strength Low-Alloy Steels before and after Annealing

Surface analyses of two high-strength low-alloy steels are reported before and after annealing. The surface analysis techniques used include ESCA, AES, and SIMS. The steel samples were hand polished and cleaned before annealing; the effects of cleaning have been investigated. Samples were annealed in flowing N₂ or in vacuum at 650°C. Changes in the steel surface as the annealing time and atmosphere were changed are reported. Additionally, differences between surfaces of two steels having similar bulk compositions were investigated both before and after annealing. Cleaning high-strength low-alloy steels generally decreased carbon contamination on the surface without affecting the nature or surface concentrations of iron, oxygen, or manganese. Vacuum annealing the steel produces a steady state much faster than when the steel is nitrogen annealed; however, the composition of the steel surface after vacuum annealing is similar to the surface after annealing in flowing N₂. Although the two steels investigated have similar bulk concentrations, type B steel has much higher Mn concentration on the surface than type A steel. The amount of Mn on the surface appears to affect the surface concentrations of Fe and O as the sample is annealed.