Influence of laser polishing in an inert atmosphere on the high cycle fatigue strength of AISI 1045 steel

• The paper deals with the influence of laser polishing in N2 on the fatigue life.
• Experimental tests have been done on untreated and laser polished specimens.
• We demonstrate that laser polishing in N2 atmosphere barely affects the fatigue limit.
• There is a reduction in the fatigue strength in the finite-life zone.
• Data and coefficients useful for fatigue calculations are provided.

This paper presents a study of the high-cycle fatigue behaviour of normalised 1045 AISI steel after laser polishing in a N2 atmosphere. When laser polishing is done in air, the surface layer has pores, inclusions and oxides, which are detrimental to the fatigue strength; however, laser polishing in N2 produces better surface features and fatigue-behaviour. With the laser parameters used in this study, a heat-affected zone of about 100 μm appears in the surface where the residual stresses are compressive. In this zone, the metallurgical structure is martensitic and ferritic because the pearlitic zones have changed to martensitic during the laser-polishing process, while the ferritic ones have remained unchanged. Fatigue tests showed that the fatigue strength is scarcely affected by laser polishing in N2. This paper also provides quantitative data and calculation procedures useful for the fatigue analysis of 1045 AISI steel components finished by laser polishing in an inert atmosphere.