This paper presents two methods of introducing boron into the surface layer of iron alloys, namely diffusion
boronizing by means of the powder method and laser alloying with a TRUMPF TLF 2600 Turbo CO2 gas
laser. Amorphous boron was used as the chemical element source. As regards diffusion drilling, the influence
of temperature and time on the properties of the layer was tested. During the laser alloying, the influence of the
thickness of the boriding paste layer as well as the power and laser beam scanning velocity was determined. How
the carbon content in steel and alloying elements in the form of chromium and boron influence the structure of
the surface layer was tested. To achieve this object, the following grades of steel were used: C45, C90, 41Cr4,
102Cr6, and HARDOX boron steel. The microhardness and wear resistance of the obtained boron-containing
surface layers were tested. A Metaval Carl Zeiss Jena light microscope and a Tescan VEGA 5135 scanning
electron microscope, a Zwick 3212B microhardness tester, and an Amsler tribotester were used for the tests.
The structure of the diffusion- borided layer consists of the needle-like zone of FeB + Fe2B iron borides about
0.15 mm thick, with a good adhesion to the substrate of the steel subjected to hardening and tempering after
the boriding process. After the laser alloying, the structure shows paths with dimensions within: width up to
0.60 mm, depth up to 0.35 mm, containing a melted zone with a eutectic mixture of iron borides and martensite,
a heat affected zone with a martensitic-bainitic structure and a steel core. The microhardness of both diffusionborided
and laser-borided layers falls within the range of 1000 – 1900 HV0.1, depending on the parameters
of the processes. It has been shown that, apart from the structure and thickness of the layer containing boron
and microhardness, the frictional wear resistance depends on the state of the steel substrate, i.e. its chemical
composition and heat treatment. The results of testing iron alloys in the borided state were compared with those
obtained only after the heat treatment.
Microstructure of Fe–TiC Composite Surface Layer on Carbon Steel Formed by Laser Alloying Process