Application of the recatest test technique to assess the structural and mechanical quality of nitrided layers produced on S355 and 40HM steels, using the ReCalo2 test stand.

The paper presents a series of material tests for S355, 40HM structural steels subjected to the process of controlled gas nitriding. Within their grade, these steels are significantly differentiated by the thickness of the nitride layer and the depth of the internal nitriding zone. In the structural description of the nitrided layers, a metallographic analysis was used, including a spherical microsection (PN EN-1071-2:2004) supplemented with measurements of profile hardness with determination of their thickness HV0.5 g= r+50, g= 400 HV0.5. The mechanical quality of the layers system was assessed on the basis of tests using the Rockwell indenter test technique with an increasing load of up to 200N (ASTM C1624, ISO 20502 and ISO EN 1071). The use of the proprietary Recatest technique, which is a combination of two material tests of a scratch and a spherical microsection, allowed for a precisely describe the mechanical behavior of the structures of the nitrided layer with quantitative parameters of the deformed structures within the scratch, e.g. change in the depth of the scratch related to the load, thickness of the material of the nitride layer dented under the bottom of the scratch and others. The data is differentiated by the load of the moving Rockwell indenter, the grade of the nitrided material and the structure of the nitrided layer, and especially the thickness of the iron nitrides. The paper presents the essential design features of the Recalo2 test stand in comparison to other solutions found on the global market. [ABSTRACT FROM AUTHOR]