The Effect of Boriding Treatment on the Fatigue Resistance of X70 Steel

The boriding treatment is a very effective technique for hardening the surface to improve resistance to wear and friction, but it can also have negative effects on the mechanical properties and fatigue resistance of steel treated with this hardening technique. Boride parameters, such as temperature and holding time, affect the microstructure of the base metal and the boride layer. This study is interesting and important because understanding the effect of boriding and boriding parameters on the fatigue strength of X70 steel may have significant implications for industrial applications where fatigue is a major concern, such as offshore structures and transport equipment components. In order to better understand the effects of the boriding process on fatigue resistance, we carried out a series of fatigue tests on samples of X70 steel that had undergone different treatments. Three treatments were carried out, such as boriding treatment alone; direct quenching alone, and boriding followed by direct cooling. After analyzing the test results, we can evaluate the effect of each treatment on the fatigue properties of X70 steel and determine the optimal treatment combination to improve service performance. The results showed that boriding treatment followed by direct quenching has higher fatigue resistance than boriding treatment alone. Experimental data from microhardness tests showed that direct quenching after boriding increased the hardness of the base metal after boriding, which made it possible to obtain a balance between the surface hardness and the hardness of the interior of the metal. The morphology, microstructure, thickness of the borided layer, and crack origin sites were determined by means of the scanning electron microscope (SEM), an optical microscope, and microhardness by a microhardness tester.