The influence of wave strain hardening on the corrosion resistance of welded joints of structural steels in agricultural machinery

BACKGROUND: Corrosion damage to structural steels, especially in welded joints of agricultural machinery, leads to significant economic losses (3-5% of GDP). In addition to the main conventional methods of corrosion protection (painting, galvanizing), the technology of manufacturing (hardening) of parts has a significant impact on corrosion resistance. The effect of surface plastic deformation (SPD) on corrosion resistance remains insufficiently studied, especially for welded joints of steels of the agricultural industry. AIM: Definition of quantitative patterns of the influence of wave strain hardening (WSH) parameters on the corrosion resistance, microstructure and microhardness of structural steels (09G2S, 30KhGSA, 40Kh, 45, 10HSND) and their welded joints for the development of optimal processing conditions. METHODS: Five grades of agriculture-purposed structural steels (09G2S, 30KhGSA, 40Kh, 45, 10KhSND) and their welded joints were studied. The samples were subjected to wave strain hardening (WSH) with variable processing parameters. Corrosion resistance was assessed by weight loss after salt fog tests. The microstructure (grain size, defects) was analyzed using optical microscopy. RESULTS: Experimental studies have revealed the dependence of the effect of wave strain hardening on corrosion resistance depending on the steel grade. For alloy steels (30KhGSA, 40Kh, 10HSND, 09G2S), WSH can both increase and decrease resistance depending on the processing conditions and the type of sample (base metal or welded joint). The maximum improvement in corrosion resistance reached 42%. On the contrary, for carbon steel 45, the use of WSH led to a decrease in corrosion resistance by 26–35%. CONCLUSION: WSH effectively increases the corrosion resistance of alloy steels (up to 42%), but requires individual selection of processing modes (including the overlap coefficient) for each material and type of joint. The use of WSH on carbon steel 45 is not recommended due to a decrease in corrosion resistance.