Surface laser alloying can improve mechanical behaviour, particularly hardness, wear or corrosion resistance. Here, different boron coatings - boron carbides, boron, boron-iron or zirconia-boron mixtures - on a chromium-molybdenum steel are laser melted; the laser tracks show rather homogeneous microstructures; hardness increases with boron content and can reach about 1200 HV over a one millimeter depth with 5.7% boron, without the formation of the brittle phase FeB.