Laser boronising of Ti-6A1-4V as a result of laser alloying with pre-placed BN

This paper discusses the effect of CO2 laser alloying of pre-placed BN coat ing with Ti-6Al-4V alloy. The formation of titanium boride and titanium nit ride investigated using energy dispersive X-ray diffraction (EDXRD) result were related to the microhardness and microstructure. The nitrogen and boro n diffusion during the laser boronising process identified using secondary ion mass spectrometry (SIMS) and X-ray photoelectron spectrometry (XPS) ana lysis was compared with the EDXRD results. The surface hardness HV1500-1700 observed at the boronised layer was five to six times higher than that of untreated Ti-6Al-4V alloy. This was compared with needle platelet and dendr ite type microstructures. Theoretically estimated surface temperature value s were used to interpret the compound formation in the laser alloyed layer. (C) 1999 Elsevier Science S.A. All rights reserved.