Use of Hexagonal Boron Nitride in Automotive Friction Materials

The major goal of this research study was to address the possible replacement of copper and selected solid lubricants by environmentally friendly hexagonal boron nitride (h-BN). Model friction samples were manufactured and subjected to friction assessment and screening tests (FAST) and full scale automotive brake dynamometer (Dyno) tests. The SAE recommended J2430 procedure provided the necessary data for the Brake Effectiveness Evaluation Procedure (BEEP) by Brake Manufacturers' Council. The obtained results indicate that the overall coefficient of friction, as detected in FAST, increased with respect to baseline with a 1:1 substitution of h-BN for either Cu or metal sulfides (Sb₂ S₃ and MoS₂). The thickness losses in FAST tests were similar or lower when h-BN was being used to replace copper and metal sulfides, except for the HCR type of h-BN. Dyno (SAE J2430) results indicated that the friction level of h-BN modified samples was similar in respect to the baseline material when copper or metal sulfides were replaced by h-BN. The detected wear rates of h-BN modified samples in Dyno tests were higher when compared to the baseline material. Five out of eight samples containing h-BN meet all criteria in BEEP; the other three failed in the hot performance. The test results indicated that certain types of h-BN can be considered as prospective materials for formulations of environmentally friendly friction material.