As the high carbon high speed steel type R18 is a very abrasion resistant material due to its high hardness resulting from hard carbides and martensitic matrix .In this work we had tested , the spectra chemical composition, hardness , of that steel before and after heat treatment , and determination of phase transformation points by dilatometer during heating and cooling at the rates of 10 and 20 C˚/min. .Mechanical properties after different temperatures of heat treatments were tested. Valuable results were achieved .All results were shown in the tables (1-6) in the text, which could be considered as the continuation of many authors works, who tried other methods , in their investigations ..The main goal is to has high abrasion resistanse at high temperature during high speed machining.