This master thesis deals with surface hardening of steels, especially with rotary flash hardening of 42CrMo4 steel (WNr 1.3563, ČSN 15142). In this method homogenous heating of whole surface occurs during a very fast rotation of the component. In the theoretical part of this thesis the most common methods of surface hardening are described, with focus on laser and electron beam technologies. In the experimental part special device for this application was constructed. Rotary flash hardening was done using different radiation source and experimantal device parameters. The hardened surface layer of maximal thickness of 0,7 mm and width of 5,6 mm was achieved using laser beam. Results with electron beam were way better, because this technology allows to control the distribution of power along the beam width in order to improve the width/thickness ratio of hardened layer. Using this method maximal layer thickness of 1,4 mm and width of 13,4 mm was achieved.

In this master thesis, performed at Ovako Group R&D (Hofors) a new machining test method for ranking heats of calcium-treated steels, M-Steels, has been proposed.  A total of six different heats of 42CrMo4-M steel in the quenched-and-tempered (Q+T) condition were tested. The proposed method uses dry turning with coated cemented carbide tools at a cutting speed of 225 m/min, 2 mm depth of cut, and a feed rate of 0.35 rev/min. The machining test is tuned so that M-Steels within medium-sized bar diameters and a small hardness interval can be differentiated by monitoring the flank wear progression of the cutting tool. This method is easily taught to a CNC-operator, it mimics real workshop conditions and can be repeated with relative robustness and ease of execution. It is possible to get a ranking where both the M-Steel treatment and hardness are included.  The major differentiator of tool wear performance was found to be a combination of wear of the outermost Al2O3 coating and the build-up and renewal of protective slag deposits on the tool rake. The rake face wear was found similar between the M-Steels samples, so it is thought that the effect of the slag deposits, as thermal barriers, affect the plastic deformation and wear of the flank face. Given the slag deposits sub-micron thickness, this indirect method of recording the flank wear is highly recommended to showcase the positive effects of the M-Steel in machining The inclusion content was evaluated according to ASTM E45 and with a scanning electron microscope (SEM) automated inclusion assessment. The link between the machinability performance of the M-Steels and their inclusion characteristics could not be clarified in this work.  Teknisk-naturvetenskapliga fakulteten

The goal of the thesis is wear analysis of cutting inserts used for machining 42CrMo4 steel. Theoretical part of the thesis contains comparison of turning and milling machining processes, machining methods for ball screws made of 42CrMo4 and description of experimental methods of tool wear analysis. Experimental part of thesis contains methodology of cutting inserts wear measurement for chosen machining method. The following testing is focused on cutting insert wear as well as workpiece surface analysis. Thesis is finished with processing of measured data and overall evaluation of achieved results.