【摘要】：LD鋼是一種新型的冷作模具鋼,已廣泛應用于模具制造業(yè)。但是模具鋼常處于高應力、高沖擊力作用下易被磨損,模具使用壽命不高,對其進行表面強化可以有效提高表面硬度和耐磨性。在眾多表面強化方法中TD鹽浴法具有設備簡單、強化效果好等優(yōu)點,故TD法已成為提高模具耐磨性的有效途徑。本文通過對LD冷作模具鋼進行TD鹽浴法制備碳化釩涂層,探究了滲釩工藝對滲釩層組織、物相及性能的影響,并探討滲釩層形成機制;研究不同磨損試驗條件下滲釩層的摩擦磨損行為和磨損機制。同時研究稀土添加量對滲釩層組織和性能的影響。研究結果表明:鹽浴最佳基礎配方為:78 Na2B4O7+8 V2O5+4 Al+10 NaF,wt.%;不同溫度、時間工藝下制備得到的滲釩層物相均為VCx相,覆層厚度和顯微硬度隨滲釩溫度的升高而增加,覆層厚度和顯微硬度值隨TD鹽浴滲釩處理時間增長而增加。LD鋼最佳滲釩工藝為950℃×8 h,該工藝下得到的滲釩層厚度約為6.1μm,顯微硬度值約為1975 HV,約為原始試樣顯微硬度值的2.63倍。950℃時滲層的生長動力學曲線滿足類拋物線形方程l2.632=13.657t,形成的碳化釩晶粒為等軸晶粒。隨著載荷和滑動速度的增加,滲釩試樣和原始試樣的摩擦系數均逐漸降低,在8.2 N載荷下,滲釩后試樣的磨損體積約為原始試樣磨損體積的1/10~1/9。在不同滑動速度條件下,滲釩試樣的體積磨損量均約為原始試樣體積磨損量的1/8~1/7,故LD鋼經TD鹽浴滲釩處理后,耐磨性得到了有效提高。滲釩層磨損機制主要為疲勞磨損和粘著磨損。950℃×8 h TD鹽浴稀土滲釩工藝中稀土最佳添加量為4%,其滲層厚度和硬度分別為7.5μm和2235 HV,與普通滲釩相比,分別提高了29.3%和22.8%。此外,添加4%稀土后滲層表面晶粒尺寸約為0.32μm,未添加稀土滲釩層表面晶粒尺寸約為0.57μm,故添加稀土后具有明顯的細化晶粒作用。
[Abstract]:LD steel is a new type of cold working die steel, which has been widely used in die manufacturing industry. However, die steel is often subjected to high stress and wear under high impact force, and the service life of die is not long. Surface strengthening can effectively improve the surface hardness and wear resistance. Among many surface strengthening methods, TD salt bath method has the advantages of simple equipment and good strengthening effect, so TD method has become an effective way to improve the wear resistance of dies. In this paper, vanadium carbide coating was prepared by TD salt bath method on LD cold working die steel. The effect of vanadizing process on the microstructure, phase and properties of vanadizing layer was investigated, and the formation mechanism of vanadizing layer was discussed. The friction and wear behavior and wear mechanism of vanadium layer under different wear test conditions were studied. At the same time, the effect of rare earth addition on the microstructure and properties of vanadium layer was studied. The results showed that the optimum basic formula of salt bath was: 1: 78 Na2B4O7 8 V2O5 4 Al 10 NaF,wt.%; at different temperatures, and the vanadium layer prepared by the reaction of different time was VCx phase, and the thickness and microhardness of the coating increased with the increase of vanadium temperature. The coating thickness and microhardness value increase with the increase of TD salt bath vanadizing treatment time. The optimum vanadizing process for LD steel is 950 鈩，

本文編號：2224764