There are various ways in which the surface of the Tool steel can achieve higher hardness.This process varies from one steel to another and careful study must be made on the steel,its properties and the application to which they will be put before a final decision on the method is reached. The various ways are:

* Nitriding,
* Flame Hardening,
* Carburizing,
* Powder carburizing,
* Gas Carburizing,
* Nitro Carburizing,
Special treatments like Sub Zero cooling are also used to improve the tool life.

Surface Treatment methods:

Method	Temperature   C	Properties achieved	Layer thickness	Surface Hardness (HV)
Carburizing box   Salt bath   Gas   Cabonitriding	860-900   860-900   890-950   820-870	Very good results   from   low content steels	Upto 2mm	900(Max)
Nitriding-Gas   Salt bath   Nitrocarburizing   Ion Nitriding	510-530   570   570	Surface hardness,   wear   resistance retention   to   tempering increase	Upto 1mm	1200(Max)
CVD	950-1100	Starts with polished   surface, follows with   vacuum hardening	0.006-0.009mm	3500(Max)
PVD	400-500	Hardened and   tempered   tools, starts with   highly   polished surface, no   change in dimensions	0.002-0.005mm	2000-2500
Oxidizing	300-350	To form oxide layer   on   surface of hot work   tool steels	Upto 0.01mm