In order to obtain the thicker austenite layer with both high content of nitrogen and homogenous microstructure on surface of the duplex stainless steels,it is necessary to develop an appropriate high temperature nitriding technology.

With the nitriding temperature increasing the layer thickness increased,the surface phases gradually precipitated CrN and γ′ from the prime α′N and ε,the surface hardness improved and the wear resistance raised.

The study proves that utilizing high temperature reinforcing carburizing,higher temperature sub balance carbon potential diffusion and pre cooling quenching can effectively increase the speed of carburizing improve diffusion layer structure and eliminate carburizing grinding crack.

Based on the analysis of reservoir damage and the results of lab experiment,five wells in BZ34 oilfield with low permeability and high temperature are treated by multi-hydrogen acid system.