| 摘要: | 本研究選用BASF-Catamold MIM 4140 (42CrMo4)之金屬粉末作為射出材料，並射出拉伸試棒，在經過五個不同溫度進行燒結處理，隨後測量拉伸試棒之密度挑選出適合的燒結溫度，再進行均質化處理，以提高材料硬度、耐磨性和內部均勻性。接著，將拉伸試棒分為未珠擊和已珠擊兩個種類，透過珠擊條件變化，進行Hv硬度測試。根據Hv硬度測試結果，利用田口法進行最佳化實驗設計，選出最佳實驗組。最終，對拉伸試棒進行珠擊後滲氮熱處理、僅滲氮熱處理、淬火與回火後珠擊再滲氮熱處理和淬火與回火接續滲氮熱處理，隨後進行Hv硬度測試和拉伸試驗，以比較其Hv硬度、微觀結構和拉伸性質。
實驗結果顯示，為了減少淨零碳排需求，從密度測試中挑選出適合的燒結溫度為1340 ℃。在均質化處理後，經過珠擊後的拉伸試棒，由硬度測試(熱處理前)的結果得知，Hv硬度值在深度0.1 mm處會隨著珠擊條件中的粒徑、壓力與時間的增加而增加。透過硬度測試(滲氮熱處理前)的Hv硬度值進行田口法最佳化，得出的最佳組合為L18(2¹×3²)直交表中的第18組。經過僅滲氮處理的試棒以及淬火與回火接續滲氮處理的試棒，表面硬度皆顯著提升，而先珠擊後進行滲氮熱處理能進一步提升表面硬度，從硬度結果(滲氮熱處理後)得知，相比僅進行滲氮熱處理，先珠擊後滲氮熱處理的試棒硬度可提升約113%；相比僅進行淬火與回火接續滲氮熱處理，先淬火與回火後珠擊再滲氮熱處理的試棒硬度可提升約59%。由於這兩種處理方法對試棒硬度均可提升超過50%，若將目前滲氮熱處理的六小時縮短50%即三小時，其硬度仍可與原來製程時間的硬度相當，而依據硬度的需求可以選擇不同的珠擊條件，從而減少能源消耗與碳排放，有助於實現節能減碳的目標。最後，由拉伸試驗結果得知，兩種滲氮熱處理的抗拉強度與延伸率之最高與最低分別為未珠擊組別與L18組別18，其中，在淬火與回火後接續滲氮熱處理未珠擊組別中的降伏強度、抗拉強度與延伸率表現最為均衡，分別為1015.7 MPa、1197.8 MPa與7.6 %，由該組別達到了所制定的目標，適合需要優良機械性質而不需提升表面硬度的應用。
;This study used BASF-Catamold MIM 4140 (42CrMo4) metal powder as the injection material. Tensile samples were injected and sintered at five different temperatures. Then, the density of the samples was measured to select the suitable sintering temperature and homogenize the samples to improve the hardness, abrasion resistance, and uniformity of the internal distribution of the material. Next, the test bars were divided into two categories, without shot peened and shot peened, for shot peening tests and Hv hardness tests. Based on the results of the Hv hardness tests, Taguchi′s method was used to optimize the experimental design and select the best experimental group. Finally, the test bars were subjected to nitriding heat treatment after shot peening, nitriding heat treatment only, quenching and tempering followed by shot peening before nitriding heat treatment, and quenching and tempering followed by nitriding heat treatment, subsequently, Hv hardness testing was conducted. Finally, tensile testing was used to get the ultimate strength, and then the microstructure was observed at crack.
The experimental results showed that a suitable sintering temperature of 1340°C was selected from the density test to minimize the need for net zero carbon emissions. The hardness test results (before heat treatment) found that the Hv hardness value at a depth of 0.1 mm increases with increasing grain size, pressure, and time in the shot peening condition. Taguchi′s method of optimizing the Hv hardness values from the hardness test (before heat treatment) resulted in the optimum combination of group 18 in the L18 (2¹×3²) orthogonal array. The surface hardness of the nitrided test bars and the quenched-and-tempered test bars both increased significantly. Additionally, nitriding heat treatment after shot peening further increased surface hardness. According to the hardness results (after nitriding), the hardness of the shot peening test bars increased by approximately 113% compared to nitriding alone, and by about 59% compared to the quenched-and-tempered test bars. When comparing quenching and tempering followed by nitriding with the combination of shot peening and nitriding after quenching and tempering, the latter improved hardness by approximately 59%. Since both treatments increase the hardness of the test bars by more than 50%, shortening the current nitriding heat treatment time by 50% (to 3 hours) could still achieve comparable hardness to the original process. Additionally, different shot peening conditions can be selected based on hardness requirements, reducing energy consumption and carbon emissions, and helping to achieve the goal of energy conservation and carbon reduction.
Finally, the tensile test results showed that the highest and lowest tensile strength and elongation in the two nitriding treatments were found in the without-shot-peened group and the L18 group 18, respectively. In particular, the yield strength, tensile strength, and elongation in the without-shot-peened group of the nitriding treatment after quenching and tempering were the most balanced, with respective values of 1015.7 MPa, 1197.8 MPa and 7.6 %. This makes it the most suitable for applications requiring hardening, meeting the targets for applications that demand excellent mechanical properties without needing to further increase surface hardness. |
