The different advantages of alloy steel are as:

(a) Higher strength, toughness and hardness upon surface and over bigger cross-section.

(b) Better harden-ability and retention of hardness at higher temperature as good for creep and cutting tools.

(c) Higher resistance against oxidation and corrosion.

The properties of plain C affected by the alloying elements steel in four ways:

(a) Via strengthening ferrite whilst forming a solid solution. The strengthening effects of several alloying elements are in this order as: Chromium, W, V, Mo, Nickel, Mn and Si.

(b) Via forming carbides that are stronger and harder. Carbides of Chromium and V are hardest and strongest against wear mostly during tempering. High alloy tool steel employs such effect.

(c) Nickel And Mn lowers the austenite formation temperature whilst other alloying elements raise this temperature. Mainly elements shift eutectoid composition to lower C percentage.

(d) Mainly elements shift the isothermal transformation curve like TTT to lower temperature, consequently lowering the critical cooling rate. Mn, Nickel, Chromium and Mo are prominently effective in this respect.