Development of an abrasion resistant steel composite with in situ TiC particles

Particles of crushed ferrotitanium (FeTi) were mixed with three iron-base p owders of different carbon and alloy content as well as some graphite to ob tain a metal matrix composite (MMC) by hot isostatic pressing (HIP) or hot uniaxial pressing (HUP) and an in situ transformation of the FeTi particles to TiC. In situ means "at the same site or position", i.e. a phase change within the particles by an inward diffusion of carbon. The HUP specimens we re not fully dense but useful to study the microstructural transformation i n time. Already after 4 min at 1000 degreesC, a hard TiC case had formed ar ound the FeTi particles, the thickness of which increased up to 300 ruin. I ron and other impurities were enriched in the particle core, which did not transform to TiC. Pin-on-dise test with fully dense HIP specimens against f lint, Al2O3 and SiC of 80 and 220 mesh size at room temperature revealed th at the abrasive wear resistance of the new MMC with 10 vol.% in situ TiC pa rticles, 63-100 mum in size and dispersed in a hardened steel matrix, was s uperior to a reference MMC with CrB2 and close to one with WC/W2C. A commer cial MMC with 50 vol.% TiC particles of 1-4 mum in size showed a considerab ly lower wear resistance than the in situ MMC. Measuring the microhardness and specific scratch energy up to 600 and 700 C, respectively, indicate a p otential of in situ TiC for elevated temperature service. The design of in situ MMC for wear protection is discussed, which is based on the larger siz e of in situ TiC particles compared to conventional ones and on the cost re duction. (C) 2001 Elsevier Science B.V. All rights reserved.