Dr Nijhawan has made notable contribution in iron-making and pneumatic steel-making techniques, austenitic grain size control and abnormality in steels. He has developed several substitute families of ferrous and non-ferrous alloys, including stainless steels. He has been responsible for the setting up of heavy integrated pilot plants at the National Metallurgical Laboratory. Dr Nijhawan has also done valuable work for ferrous and non-ferrous metallurgical industries in the public and private sectors.