Preliminary search on iron alloys boriding by means of P.T.A.

Low carbon steel (AISI 1010) samples were submitted to the P.T.A. technique using a Fe–B powder (8=13.5% wt.). The coatings consist of FnB orthorombic boride crystals that, in the outermost part, are surrounded, at the grain boundary, by FeB tetragonal boride and that, in the inner part, are embedded in the Fe–B–C ternary eutectic (Fea–Fe3BxC1–x–Fe2B). The relative abundance of the eutectic increases in relation to the distance from the external surface. Microhardness measurements, taken throughout the coating depth, gave constant values (about 1,300 HV0.1) similar to those characteristic of Fe2B boride. Annealing treatments in inert gas at 1,273 K for different times (2÷24 h) showed no modification in the constituent phases and microhardness values.