This book emphasizes that there are various modes of wear, erosion, and friction, and it should be clear at this point that dealing with abrasion problems requires a very different solution than dealing with cavitation problems. However, there are rather limited options that engineers and maintenance personnel have in fixing an existing tribology problem or a perceived one. They can try to identify a material that resists a particular mode of wear or erosion without a coating or surface treatment, or they can try to identify a substrate and coating or treatment that will do the job. This chapter is about the former: materials that can solve tribology problems unaided; they do not need to be coated or surface treated, but may require ordinary heat treatments for through hardening. They are materials that can be purchased “off the shelf” and used.