Wear resistant alloys for coal handling equipment. Progress report, January 1--September 30, 1977

Abstract

The in-service operating conditions of coal transport and fragmentation equipment involve various combinations of dry or liquid slurry abrasion, impact loading, and temperatures that may vary from ambient to elevated (500/sup 0/F--1000/sup 0/F). Both 2-body and 3-body abrasive wear can be encountered. The published literature contains little information on testing materials under the various abrasive conditions that are of concern, especially 3-body wear. However, a number of tests were identified which may serve to provide wear data under different service conditions. A dry abrasive wear tester, to be used for screening alloys, was constructed. A review of the alloy steel literature was completed and was used to select low-alloy and secondary hardening steel compositions for screening. Initial screening criteria included the stipulation of a hardness of R/sub c/55 with an impact toughness of around 15 ft lbs or a fracture toughness of 80 KSI..sqrt..in., depending on the application being considered. Several of the steels that were evaluated to date appeared to meet these criteria. A systematic development of secondary hardening steels has been evolved and it has been shown that good combinations of strength and toughness were achieved through proper composition and microstructural control. These higher alloyed steels appear to be suited for long-term, elevated-temperature service. The lower alloy Cr-Ni-Mo and Cr-Si-Mo steels investigated also exhibited good combinations of strength and toughness and may be suitable for ambient temperature use.