Boronizing is a kind of surface hardening thermo chemical treatment in which boron atoms are diffused into a material surface and produce the hard phase boride. In comparison with other treatment, this treatment has advantages like producting harder phase on material and lower friction coefficient. In this study, powder boronizing methode was used for boronizing St37 steel. Mixedpowder wascontainingboric acidas boron sourceandother materials, including aluminaasasdiluents,cryoliteasactivatorandmagnesiumas reducing agent. Boronizing was carried out at 900, 950 and 1000°C for 2, 4, and 6 hours. In order todeterminephaseformedon the surfaceX-ray diffractionanalysewas carried outonaborided sample. Thento showtexturedboridelayer,about 30micronsfrom the surface was removedbyemery paper andX-ray diffractionanalysewas carried out again. The results showed thatafter thetreatment,Fe 2 B singlelayeronthe steel surfaceis formed. Also in the following sectionsof this layer, there is textureof the (002) plains. Opticalmicroscopy imagesofcross-sectionsof samplesshowedthatwith increasing duration oftreatment from 2to6 hoursandtemperature from900 to 1000°C the boride layerthickness increased from 35 to 105 micron.Hardness measurements were performed on the cross-section of the samples. The hardness of boride layers was between 1500-2400 HV and it faced with a sudden drop by moving from the surface to the inside. To study of samples wear resistance, wear test was performed on three samples including untreated, coated at 900°C for 2 hours, and coated at 1000°C for 6 hours.The results showedthat the borided samples weight lossis much smallerthan untreated sample so that the weight loss of coated sample at 900°C for 2 hours was 20 times less than the untreated sample. With increasing boride layer thickness, the wear resistance increased significantly.The coated sample at 900°C for 2 hours in load of 10 kg, after 200 meters had about 1.6 mg weight loss, while the coated samples at 1000°C for 6 hours in the same load, after 1000 meters showed weight loss of about 0.2 mg. Keywords: Surface treatment, Boronizing, Acid boric, Boride layer, Wear
