Laser surface hardening of austenitic stainless steel

For the purpose of studying the possibilities of increasing the wear resistance, keeping a high level of corrosion strength, austenitic stainless steel specimens mainly containing 19.2%Cr and 9.4%Ni were two-step surface alloyed using added materials (AMs) with hard particles of carbides (WC), nitrides (TiN), and borides (TiB₂). The simultaneous melting of AM and surface layer was performed by a CO₂ continuous wave laser on a numerically controlled X-Y table. On these specimens, the microstructural characteristics, microhardness, and depth of the molten zone were determined, which allowed definition of the AM with the best hardening effect. The research continued by two-step laser surface alloying of the same base material with different effective AM quantities. The specimens were processed by continuous wave laser radiation, by multiple-pass with 35% overlap. The alloyed layers were described by light optical microscopy, x-ray diffractometry, flash spectrometry, and hardness measurement. The conditions to obtain compact surface layers with 2.5 to 3 times higher hardness than the base material were determined.