Tribomechanical, and microstructural morphological analysis of nitride ferrous powder metallurgy composites for enhanced automotive valve guide performance

Abstract

The growing challenges of reducing exhaust emissions and improved fuel economy has triggered automotive engineers to design and manufacture engine parts with superior mechanical properties and dimensional accuracies. Valve guides are cylindrical structures supporting inlet valve and exhaust valve stems during operation. Conventionally made of grey cast iron material, valve guide suffers from severe wear losses leading to loss of fuel and increased emissions due to improper valve stem seating. Here, the synthesis of a novel ferrous powder metallurgy composite is presented and wear characteristics have been studied at varying loads of 30 N, 40 N and 50 N and varying sliding speeds of 0.5 m/s, 1 m/s and 2 m/s under lubricated conditions. The samples have undergone nitriding heat treatment at 1150 °C to improve surface hardness to 700 Hv. The samples have shown negative wear rates due to high hardness and capillary action of lubricating oil and exhibited stable friction coefficient values. This has been attributed to the formation of hard phases Fe2N, Fe3N, and Fe4N and Fe(Mn)3C and twinning-induced plastic compounds like (Fe24Mn) 0.08 as evident from XRD analysis. The morphological analysis of worn out samples was done with SEM Coupled with EDS and it showed micro-cutting, Ploughing, and delamination as main wear phenomenon.

Keywords

• Powder metallurgy
• Pin of disc
• Sliding wear
• Synthesis
• Ferrous
• Lubrication