The effect of boronizing on mechanical properties of ferrous materials produced by powder metallurgy

Ferrous materials produced by powder metallurgy (PM) is used widespread in automotive industry, because they have net shape without machining and extend cost saving. Economic life of many structural parts is limited by wear. The demands have increased hardness and wear resistance on the surface and higher toughness in the core than those of common parts made of low carbon steel. Boronized steels have great abrasive wear resistances, since they have high hardness. Their hardness are higher than nitriding and carburetion steels. Usually boronized coating hardness on yields, made of ferrous, guard at high temperature comparate of nitriding coating and with boronizing coefficient of friction is around Teflon. In this study, the effect of boronizing duration and surface roughness on mechanical properties of the coatings for different P/M products with Fe–4Ni–1.5Cu–0.5Mo chemical compositions was investigated. In this purpose, 2 groups of P/M products with different density and surface roughness were produced by cold pressing and sintering. All of the specimens were subjected to boronizing process at 950°C for 2, 4 and 6 hours. Cross-sections of the boronized specimens were observed by optical microscopy in order to determine thickness of the FeB layers. The effect of boronizing duration, surface roughness and density on surface hardness, on wear resistance and on fracture toughness was determined.