Prakt. Met. Sonderband 38 (2006) 387 
An investigation on the effects of various etchants, etching 
techniques and etching time on the microstructure of Sandvik 
1RK91 stainless steel 
H.Arabi*, J. Samei**, M.Abbasi**, M.Bigdeli***, A.Khosravani*** 
* Department of Material Science and Engineering, Iran University of Science and 
Technology, Tehran, Iran. 
**Mechanical Engineering Department, Material Science and Engineering Group, 
K.N.Toosi University, Tehran, Iran. 
**Material Science and Engineering Department, Sharif University of Technology, Tehran, 
Iran. 
Abstract 
Current studies on the microstructure of Sandvik 1RK91 stainless steel have almost been 
accomplished by scanning and transmition electron microscopes. So there is only a little 
information available on the optical metallography of this steel. Existence of considerable 
amounts of Cr, Ni and Mo in Sandvik steel composition renders it highly corrosion resistant 
steel. Mo has a highly anticorrosive effect on the property of steels in presence of Cl ions. 
Therefore only a few etchants are capable of etching this type of steel. In order to study 
the effects of various etchants and etching time on this type of steel, thirteen samples with 
different compositions were selected. Then they were subjected to different etchants at 
various time to see the effects of these parameters on the revealed structure of the 
samples. Optimum etching time for each etchant has been achieved by trail and error. 
Also to study the effects of the amount of cold work on etching time some samples were 
cold rolled. Results of this study show that by increasing the amount of cold work, the 
amount of etching time decreases in general. However the amount of decreases in etching 
time not only depends on the amount of cold work but also on the used etchant. Worth 
mentioning, the effects of various etching techniques such as normal, hot, electrolytic and 
thermal etching in addition to the above mentioned parameters on revealed structures 
were studied too. Finally appropriate etchants, etching time and etching techniques to 
reveal martensite, austenite, grain boundaries, twin boundaries etc, have been outlined for 
each sample. By studying and comparing the images obtained from various samples, 
some results show that Fry reagent to reveal martensite when normal etching is used and 
Nitric acid for grain boundaries and Hydrochloric acid for twin boundaries when electrolytic 
etching is used and V2A reagent to reveal general structure when hot etching is used, are 
effective. 
1. Introduction 
Stainless steel Sandvik 1RK91, is a new generation of maraging stainless steel that has 
been produced by AB Sandvik Co. recently [1]. This type of steel has approximately 0.01 
wt% of carbon and a nominal chemical composition of 12Cr-9Ni-4Mo-2Cu [1-3]. After 
casting these steels are normally subjected to solution annealing at 1000 °C, following by 
ageing at 400-500 °C [2,3].