Enhanced wear and corrosion resistance of high-speed laser-clad automotive brake discs for Euro-7 compliance

Abstract Meeting the Euro 7 brake particle emission limit of 7 mg · km −1 requires brake discs that combine high durability and minimal wear. This study systematically investigates the efficacy of high-speed laser cladding (HSLC, <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mn>5.6</mml:mn> <mml:mspace width="0.25em"/> <mml:mi mathvariant="normal">m</mml:mi> <mml:mo>·</mml:mo> <mml:msup> <mml:mrow> <mml:mi mathvariant="normal">min</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>1</mml:mn> </mml:mrow> </mml:msup> </mml:math> ) for enhancing the wear and corrosion resistance of automotive brake discs fabricated from GG25 grey cast iron. Three distinct metal matrix composite (MMC) coatings were developed via laser cladding: Disc-1 employed a 431L stainless steel matrix reinforced with TiC, CrC, and B 4 C ; Disc-2 utilized a CoCrMo matrix with CrC and B 4 C ; and Disc-3 incorporated a NiCrSi matrix supplemented with WC and B 4 C . After controlled grinding, all coatings attained a uniform thickness of ≈400 μ m. Microstructural characterization by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) confirmed the formation of a dense, homogeneous clad layer with a robust metallurgical bond to the substrate. Mechanical testing showed that surface hardness rose from Disc-1 (550 ±50 HV) to Disc-2 (615 ±45 HV) and Disc-3 (675 ±55 HV), correlating with improved wear resistance and friction stability (COF ≈ 0.45 across 100–500 °C). Salt-spray (ASTM B117, 5% NaCl) endurance reached 275 h for Disc-2 and 235 h for Disc-3,confirming strong chloride resistance. Combined disc plus pad wear remained &lt;0.5 g for all coatings, while an economic analysis indicated that Disc-3 offers the best performance to cost ratio (relative cost = 0.5). The simultaneous improvements in COF, wear mass and corrosion life imply brake particle emissions below the Euro 7 threshold, positioning HSLC MMC coatings as the first single-process route to achieve Euro 7 compliance under service conditions.