Manganese steel for high-impact crushing wear where work hardening does the job. Martensitic and high-chrome white iron where abrasion dominates and impact stays low. Cast steel for structural frames and housings.
Grade chosen against the actual impact-to-abrasion balance, because hardness alone is the wrong specification. Wear parts matched in sets where mating geometry decides service life. Heat treatment, machining, and NDE in-house.