Research on lubricity of oils containing the hexagonal boron nitride

The paper presents the test results of lubricity properties of Hydrol L-HL 32 hydraulic oil, Mobilube 1 SHC 75w-90 gear oil, and two base oils: SN-150 and SN-650, containing hexagonal boron nitride. To conduct the required tests, a four ball machine was used. This device is commonly used when assessing lubricity properties of oils and greases. The following normative lubricity parameters were defined: the value of welding point Pz [daN], the value of last non-seizing load Pn [daN], the value of seizing at smoothy growing load Pt [daN], as well as the wear limiting capacity load Goz [daN/mm2]. Furthermore, several non-normative tests were completed that covered indication of two parameters making it possible to complete an assessment of lubricity properties of oils. Based on the tests, it was determined that hexagonal boron nitride is a good additive that improves lubricity properties. Improvement in the above properties was recorded both in the case of hydraulic oil and gear oil, as well as oil bases. Relatively better improvement results were obtained in the case of oil bases, where the improvement in the results after using boron nitride, was more visible than in the case of hydraulic and gear oil. The best improvement results for hydraulic oil were obtained after adding 4% h-BN, whereas in the case of the SN-150 oil base, this value was 2% h-BN. The best improvement results for gear oil and SN-650 oil base were also obtained after adding 4% h-BN. The possibility of using the values of h-BN bigger than 4% was excluded. It was determined that bigger content of h-BN in oil generates negative effects (under four ball conditions). Keywords: tribology, lubricity, boron nitride.