The effects of laser pulse energy and focal point position on laser surface hardening of AISI 410 stainless steel

In this paper the capability of laser surface hardening of martensitic stainless steel AISI 410 is conducted by using a Nd:YAG pulsed laser with a maximum power of 700 W. Focal point position (22mm to 34mm) and laser pulse energy (14.7J to 16.8J) were considered as process variable parameters. microhardness was measured in depth and surface of hardened layer. Metallography of samples was conducted in order to study the microstructure of hardened zone. Also geometrical dimensions of hardened zone (width and depth), microhandness distributions in depth and width of hardened layer, microstructure of hardened layer were investigated. Results show that by increasing laser pulse energy and decreasing the laser focal point position, the hardness and depth of hardened layer increases. Observations indicated that solid state transformation and carbide solution in steel during laser surface hardening process, improved the surface hardness. Lower delta ferrite in martensitic structure in laser hardened layer lead to higher microhardness. Maximum hardened layer of 350 µm in depth and 2208 µm in width and maximum surface hardness of 747 HV0.3 is obtained in maximum pulse energy of 16.8J.