Preliminary Investigation into Repair of High Strength Steel Using Laser Cladding
High-strength steels are used in several critical aerospace applications such as aircraft landing gear, primary structure and engine components. These steels, such as the AISI 4340 assessed here exhibit small critical crack sizes, and when they suffer in-service damage from impact or corrosion, repairing the damage is particularly challenging. One potential repair method is using laser assisted metal deposition (LAMD or ‘laser cladding’ LC), to rebuild the damaged region or the grinding depression remaining after the damage has been removed. The critical situations where these materials are used makes it essential that repairs do not introduce any degradation, such as microcracking, that could lead to failure in service. In this trial, 420 grade stainless steel cladding powder was used to produce a clad layer with both high strength and good corrosion resistance. The cladding was performed under various powder mass flow rates, traverse speeds, and laser powers. The clad thickness and the depth of the fusion zone varied, as expected, with all the cladding conditions. It was found that there was very little porosity, and importantly, no evidence of microcracking under any cladding condition. There were some small defects near the clad boundary, apparently associated with each clad pass. The absence of microcracking is a promising result, and the research will be continued to assess the effect of microstructure and defects on performance of the repaired plates.
Jian-Feng Nie and Allan Morton
R. Mohammed et al., "Preliminary Investigation into Repair of High Strength Steel Using Laser Cladding ", Materials Science Forum, Vols. 654-656, pp. 362-365, 2010