Laser treatment of the 38HMJ steel surface in a liquid nitrogen environment

摘要

Samples of the 38HMJ steel kept in a liquid nitrogen bath (LN2) at 77 K are treated by a 1 kW CO_2 laser beam of intensity of about 1.3 x 10~5 W/cm~2 on the sample surface. For thermal processing by means of the 10,6 mum radiation the transparency window of LN2 below 0.3 eV is utilised. the irradiation effects are compared with results obtained for the reference samples of the same material under standard gas shielding conditions. Measurements of microhardness HV 0.1 indicate on reduction of the heat affected zone for the LN2 case. A similar effect is observed for higher sample velocities and a value of about 700 HV is obtained in a 30 mum surface layer. Surface analysis by means of Auger electron spectroscopy confirms the lcoal nitrogen enrichment of the laser treated areas depending onthe processing conditions.