Study On The Influence Of Rifling Characteristics On The High Temperature Performance Of Gun Bore Coatings

Gun bore coating is an effective means to improve the high-temperature resistance,ablation resistance,wear resistance,and service life of the gun barrel.Up to now,the tests and analysis on the high-temperature performance of the gun bore coating are mostly based on ignoring the rifling structure,and there are few studies considering the influence of the rifling characteristics on the high-temperature performance of the coating.In order to effectively improve the tactical and technical performance and prolong the service life of the gun,it is urgent to analyze the influence of rifling characteristics on the hightemperature performance of the surface coating.In this study,the samples of electroplating Cr coating and arc ion plating Cr coating with rifling characteristics were studied.The high-temperature thermal shock performance of two-kind Cr coatings and the influence of rifling cross-section shape on the surface coating performance were analyzed by high-temperature thermal shock test and numerical simulation.The results were summarized as follows:(1)Under the thermal shock test conditions of 900℃ and 10 min,the differences in the high-temperature thermal shock resistance of two-kind Cr coatings on rifling surface are obvious,which is manifested in the thermal shock products and crack expansion speed.After thermal shock tests,a dense oxidation protective film was formed on the surface of two-kind Cr coatings,and brittle oxides with destructive effects were also detected on the surface of electroplating Cr coating.In addition,the number and expansion speed of cracks on the surface of electroplating Cr coating were significantly higher than those of arc ion plating Cr coating.The difference in thermal shock performance between the twokind Cr coatings is mainly related to the accumulated fatigue stress,thermal mismatch stress,and the inherent characteristics of two-kind Cr coatings.(2)Under the thermal shock test conditions of 900℃ and 10 min,the thermal shock damage of coating at the concave corner of the groove and the convex corner of the land was focused on.The experimental results show that under the same cycles of thermal shock test,the thermal shock damage degree of the two typical regions was always as follows: the coating at the concave corner of the groove is larger than that of the convex corner of the land.The difference in thermal shock damage between the two typical regions is mainly related to the convective heat transfer area and temperature stress concentration.(3)Under the thermal shock test conditions of 900℃ and 10 min,with the different transition angles of the rifling substrate,the thermal shock performance of the surface coating was specifically shown as follows: arc rifling was better than trapezoidal rifling,trapezoidal rifling was better than rectangular rifling.In the high-temperature thermal shock cycle simulation of ignoring the monitoring deviation caused by the fixed boundary,the equivalent stress of three cross-section shape rifling models was negatively correlated with the transition angle of the rifling substrate.That is,the larger the transition angle of the rifling substrate,the smaller the stress extreme value and average stress of the rifling model.In this study,the high-temperature thermal shock damage behavior and the performance difference of two-kind Cr coatings on the rifling surface were clarified,among which the high-temperature thermal shock performance of the arc ion plating Cr coating is more excellent.In addition,the corresponding relationship between the crosssection shape of the rifling and the high-temperature thermal shock damage of the surface Cr coating was obtained.The three designed shapes have a significant effect on the hightemperature thermal shock performance of the surface Cr coating,among which the arc rifling can effectively reduce the thermal stress extreme value of the rifling specimens.